ZIP视觉里程计参考论文及数据集下载百度网盘地址 11.42MB

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视觉里程计参考论文及数据集下载百度网盘地址.zip 大约有9个文件
  1. 基于双目视觉的视觉里程计相关论文/
  2. 基于双目视觉的视觉里程计相关论文/AV1FeaturefromAcceleratedSegmentTest.pdf 453.27KB
  3. 基于双目视觉的视觉里程计相关论文/BARSAN-IoanAndrei-RobustDenseMapping-ICRA-2018-CameraReady.pdf 3.12MB
  4. 基于双目视觉的视觉里程计相关论文/KITTI数据集最全网盘地址.txt 108B
  5. 基于双目视觉的视觉里程计相关论文/LK特征点跟踪算法.pdf 341.88KB
  6. 基于双目视觉的视觉里程计相关论文/LSD A Fast Line Segment Detectorwith a False Detection Control.pdf 2.21MB
  7. 基于双目视觉的视觉里程计相关论文/PL-SLAM：a Stereo SLAM System through the Combination of Points and Line Segments.pdf 3.27MB
  8. 基于双目视觉的视觉里程计相关论文/Robust Stereo Visual Odometry through a ProbabilisticCombination of Points and Line Segments.pdf 2.73MB
  9. 基于双目视觉的视觉里程计相关论文/金字塔L-K光流.pdf 206.53KB

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写论文整理的视觉里程计参考论文PDF，KITTI数据集下载百度网盘地址，进攻参考。
<link href="/image.php?url=https://csdnimg.cn/release/download_crawler_static/css/base.min.css" rel="stylesheet"/><link href="/image.php?url=https://csdnimg.cn/release/download_crawler_static/css/fancy.min.css" rel="stylesheet"/><link href="/image.php?url=https://csdnimg.cn/release/download_crawler_static/89541504/raw.css" rel="stylesheet"/><div id="sidebar" style="display: none"><div id="outline"></div></div><div class="pf w0 h0" data-page-no="1" id="pf1"><div class="pc pc1 w0 h0"><img alt="" class="bi x0 y0 w1 h1" src="/image.php?url=https://csdnimg.cn/release/download_crawler_static/89541504/bg1.jpg"/><div class="t m0 x1 h2 y1 ff1 fs0 fc0 sc0 ls0 ws0">1</div><div class="t m0 x2 h3 y2 ff2 fs1 fc0 sc0 ls0 ws0">PL-SLAM:<span class="_ _0"> </span>a<span class="_ _0"> </span>Stereo<span class="_ _0"> </span>SLAM<span class="_ _0"> </span>System<span class="_ _0"> </span>through<span class="_ _0"> </span>the<span class="_ _0"> </span>Com<span class="_ _1"></span>bination</div><div class="t m0 x3 h3 y3 ff2 fs1 fc0 sc0 ls0 ws0">of<span class="_ _0"> </span>P<span class="_ _1"></span>oin<span class="_ _1"></span>ts<span class="_ _0"> </span>and<span class="_ _0"> </span>Line<span class="_ _0"> </span>Segmen<span class="_ _1"></span>ts</div><div class="t m0 x4 h4 y4 ff3 fs2 fc0 sc0 ls0 ws0">R<span class="_ _1"></span>ub<span class="_ _2"></span>en<span class="_ _3"> </span>Gomez-Ojeda,<span class="_ _3"> </span>Da<span class="_ _1"></span>vid<span class="_ _3"> </span>Zuñiga-No<span class="_ _2"></span>ël,<span class="_ _3"> </span>F<span class="_ _4"></span>rancisco-Angel<span class="_ _3"> </span>Moreno,</div><div class="t m0 x5 h4 y5 ff3 fs2 fc0 sc0 ls0 ws0">Da<span class="_ _1"></span>vide<span class="_ _3"> </span>Scaramuzza,<span class="_ _3"> </span>and<span class="_ _3"> </span>Ja<span class="_ _1"></span>vier<span class="_ _3"> </span>Gonzalez-Jimenez</div><div class="t m0 x6 h5 y6 ff4 fs3 fc0 sc0 ls0 ws0">A<span class="_ _1"></span>bstr<span class="_ _1"></span>act<span class="_ _2"></span><span class="ff5">—T<span class="_ _4"></span>raditional<span class="_ _5"> </span>approac<span class="_ _1"></span>hes<span class="_ _5"> </span>to<span class="_ _5"> </span>stereo<span class="_ _5"> </span>visual</span></div><div class="t m0 x7 h5 y7 ff5 fs3 fc0 sc0 ls0 ws0">SLAM<span class="_ _6"> </span>rely<span class="_ _6"> </span>on<span class="_ _6"> </span>p<span class="_ _2"></span>oin<span class="_ _1"></span>t<span class="_ _6"> </span>features<span class="_ _6"> </span>to<span class="_ _6"> </span>estimate<span class="_ _6"> </span>the<span class="_ _6"> </span>camera</div><div class="t m0 x7 h5 y8 ff5 fs3 fc0 sc0 ls0 ws0">tra<span class="_ _2"></span>jectory<span class="_ _7"> </span>and<span class="_ _7"> </span>build<span class="_ _8"> </span>a<span class="_ _7"> </span>map<span class="_ _8"> </span>of<span class="_ _7"> </span>the<span class="_ _8"> </span>en<span class="_ _1"></span>vironment.<span class="_ _7"> </span>In<span class="_ _8"> </span>lo<span class="_ _1"></span>w-</div><div class="t m0 x7 h5 y9 ff5 fs3 fc0 sc0 ls0 ws0">textured<span class="_ _3"> </span>environmen<span class="_ _1"></span>ts,<span class="_ _6"> </span>though,<span class="_ _3"> </span>it<span class="_ _6"> </span>is<span class="_ _3"> </span>often<span class="_ _6"> </span>difficult<span class="_ _3"> </span>to</div><div class="t m0 x7 h5 ya ff5 fs3 fc0 sc0 ls0 ws0">find<span class="_ _9"> </span>a<span class="_ _9"> </span>sufficien<span class="_ _1"></span>t<span class="_ _9"> </span>num<span class="_ _1"></span>b<span class="_ _2"></span>er<span class="_ _9"> </span>of<span class="_ _9"> </span>reliable<span class="_ _9"> </span>p<span class="_ _a"></span>oin<span class="_ _1"></span>t<span class="_ _9"> </span>features<span class="_ _9"> </span>and,</div><div class="t m0 x7 h5 yb ff5 fs3 fc0 sc0 ls0 ws0">as<span class="_ _9"> </span>a<span class="_ _3"> </span>consequence,<span class="_ _3"> </span>the<span class="_ _9"> </span>p<span class="_ _a"></span>erformance<span class="_ _3"> </span>of<span class="_ _3"> </span>suc<span class="_ _1"></span>h<span class="_ _3"> </span>algorithms</div><div class="t m0 x7 h5 yc ff5 fs3 fc0 sc0 ls0 ws0">degrades.<span class="_ _0"> </span>This<span class="_ _b"> </span>pap<span class="_ _a"></span>er<span class="_ _b"> </span>prop<span class="_ _2"></span>oses<span class="_ _b"> </span>PL-SLAM,<span class="_ _0"> </span>a<span class="_ _b"> </span>stereo</div><div class="t m0 x7 h5 yd ff5 fs3 fc0 sc0 ls0 ws0">visual<span class="_ _c"> </span>SLAM<span class="_ _c"> </span>system<span class="_ _c"> </span>that<span class="_ _c"> </span>com<span class="_ _1"></span>bines<span class="_ _c"> </span>b<span class="_ _2"></span>oth<span class="_ _c"> </span>p<span class="_ _a"></span>oints<span class="_ _c"> </span>and</div><div class="t m0 x7 h5 ye ff5 fs3 fc0 sc0 ls0 ws0">line<span class="_ _c"> </span>segmen<span class="_ _1"></span>ts<span class="_ _c"> </span>to<span class="_ _c"> </span><span class="fc2 sc0">w</span><span class="_ _1"></span><span class="fc2 sc0">ork</span><span class="_ _c"> </span><span class="fc2 sc0">robustly</span><span class="_ _6"> </span><span class="fc2 sc0">in</span><span class="_ _c"> </span><span class="fc2 sc0">a</span><span class="_ _c"> </span><span class="fc2 sc0">wider</span><span class="_ _d"> </span><span class="fc2 sc0">v</span><span class="_ _1"></span><span class="fc2 sc0">ariet</span><span class="_ _1"></span><span class="fc2 sc0">y</span><span class="_ _c"> </span><span class="fc2 sc0">of</span></div><div class="t m0 x7 h5 yf ff5 fs3 fc0 sc0 ls0 ws0"><span class="fc2 sc0">scenarios</span>,<span class="_"> </span>particularly<span class="_ _c"> </span>in<span class="_"> </span>those<span class="_ _c"> </span>where<span class="_"> </span>point<span class="_ _c"> </span>features</div><div class="t m0 x7 h5 y10 ff5 fs3 fc0 sc0 ls0 ws0">are<span class="_ _c"> </span>scarce<span class="_"> </span>or<span class="_ _c"> </span>not<span class="_ _c"> </span>well-distributed<span class="_ _c"> </span>in<span class="_ _c"> </span>the<span class="_"> </span>image.<span class="_ _c"> </span>PL-</div><div class="t m0 x7 h5 y11 ff5 fs3 fc0 sc0 ls0 ws0">SLAM<span class="_ _6"> </span>leverages<span class="_ _6"> </span>both<span class="_ _6"> </span>p<span class="_ _a"></span>oints<span class="_ _6"> </span>and<span class="_ _6"> </span>segments<span class="_ _6"> </span>at<span class="_ _6"> </span>all<span class="_ _6"> </span>the</div><div class="t m0 x7 h5 y12 ff5 fs3 fc0 sc0 ls0 ws0">instances<span class="_"> </span>of<span class="_ _b"> </span>the<span class="_"> </span>pro<span class="_ _a"></span>cess:<span class="_ _e"> </span>visual<span class="_"> </span>o<span class="_ _2"></span>dometry<span class="_ _4"></span>,<span class="_"> </span>keyframe</div><div class="t m0 x7 h5 y13 ff5 fs3 fc0 sc0 ls0 ws0">selection,<span class="_ _6"> </span>bundle<span class="_ _3"> </span>adjustment,<span class="_ _3"> </span>etc.<span class="_ _6"> </span>W<span class="_ _4"></span>e<span class="_ _6"> </span>con<span class="_ _1"></span>tribute<span class="_ _6"> </span>also</div><div class="t m0 x7 h5 y14 ff5 fs3 fc0 sc0 ls0 ws0">with<span class="_ _9"> </span>a<span class="_ _9"> </span>lo<span class="_ _a"></span>op<span class="_ _3"> </span>closure<span class="_ _9"> </span>pro<span class="_ _a"></span>cedure<span class="_ _9"> </span>through<span class="_ _9"> </span>a<span class="_ _3"> </span>no<span class="_ _1"></span>vel<span class="_ _9"> </span>bag-of-</div><div class="t m0 x7 h5 y15 ff5 fs3 fc0 sc0 ls0 ws0">w<span class="_ _1"></span>ords<span class="_ _8"> </span>approach<span class="_ _7"> </span>that<span class="_ _8"> </span>exploits<span class="_ _7"> </span>the<span class="_ _8"> </span>com<span class="_ _1"></span>bined<span class="_ _8"> </span>descriptive</div><div class="t m0 x7 h5 y16 ff5 fs3 fc0 sc0 ls0 ws0">p<span class="_ _a"></span>o<span class="_ _f"></span>w<span class="_ _1"></span>er<span class="_ _d"> </span>of<span class="_ _d"> </span>the<span class="_ _d"> </span>tw<span class="_ _1"></span>o<span class="_ _d"> </span>kinds<span class="_ _d"> </span>of<span class="_ _d"> </span>features.<span class="_ _d"> </span>Additionally<span class="_ _4"></span>,<span class="_ _6"> </span>the</div><div class="t m0 x7 h5 y17 ff5 fs3 fc0 sc0 ls0 ws0">resulting<span class="_ _c"> </span>map<span class="_"> </span>is<span class="_ _c"> </span>richer<span class="_ _c"> </span>and<span class="_"> </span>more<span class="_ _c"> </span>diverse<span class="_ _d"> </span>in<span class="_"> </span>3D<span class="_ _c"> </span>ele-</div><div class="t m0 x7 h5 y18 ff5 fs3 fc0 sc0 ls0 ws0">men<span class="_ _1"></span>ts,<span class="_ _3"> </span>which<span class="_ _9"> </span>can<span class="_ _9"> </span>b<span class="_ _a"></span>e<span class="_ _9"> </span>exploited<span class="_ _3"> </span>to<span class="_ _9"> </span>infer<span class="_ _3"> </span>v<span class="_ _1"></span>aluable,<span class="_ _9"> </span>high-</div><div class="t m0 x7 h5 y19 ff5 fs3 fc0 sc0 ls0 ws0">lev<span class="_ _1"></span>el<span class="_ _7"> </span>scene<span class="_ _7"> </span>structures<span class="_ _10"> </span>lik<span class="_ _1"></span>e<span class="_ _7"> </span>planes,<span class="_ _10"> </span>empty<span class="_ _10"> </span>spaces,<span class="_ _10"> </span>ground</div><div class="t m0 x7 h5 y1a ff5 fs3 fc0 sc0 ls0 ws0">plane,<span class="_ _9"> </span>etc.<span class="_ _9"> </span>(not<span class="_ _9"> </span>addressed<span class="_ _9"> </span>in<span class="_ _3"> </span>this<span class="_ _9"> </span>w<span class="_ _1"></span>ork).<span class="_ _3"> </span>Our<span class="_ _9"> </span>prop<span class="_ _a"></span>osal</div><div class="t m0 x7 h5 y1b ff5 fs3 fc0 sc0 ls0 ws0">has<span class="_ _8"> </span>b<span class="_ _a"></span>een<span class="_ _9"> </span>tested<span class="_ _8"> </span>with<span class="_ _9"> </span>sev<span class="_ _1"></span>eral<span class="_ _9"> </span>popular<span class="_ _9"> </span>datasets<span class="_ _8"> </span>(such<span class="_ _8"> </span>as</div><div class="t m0 x7 h5 y1c ff5 fs3 fc0 sc0 ls0 ws0">KITTI<span class="_ _6"> </span>and<span class="_ _6"> </span>EuRoC),<span class="_ _3"> </span>and<span class="_ _6"> </span>is<span class="_ _6"> </span>compared<span class="_ _6"> </span>to<span class="_ _3"> </span>state<span class="_ _6"> </span>of<span class="_ _6"> </span>the</div><div class="t m0 x7 h5 y1d ff5 fs3 fc0 sc0 ls0 ws0">art<span class="_ _8"> </span>metho<span class="_ _a"></span>ds<span class="_ _8"> </span>lik<span class="_ _f"></span>e<span class="_ _8"> </span>ORB-SLAM,<span class="_ _8"> </span><span class="fc2 sc0">rev</span><span class="_ _1"></span><span class="fc2 sc0">ealing</span><span class="_ _8"> </span><span class="fc2 sc0">a</span><span class="_ _8"> </span><span class="fc2 sc0">more</span><span class="_ _8"> </span><span class="fc2 sc0">robust</span></div><div class="t m0 x7 h5 y1e ff5 fs3 fc0 sc0 ls0 ws0"><span class="fc2 sc0">p</span><span class="_ _a"></span><span class="fc2 sc0">erformance</span><span class="_"> </span><span class="fc2 sc0">in</span><span class="_"> </span><span class="fc2 sc0">most</span><span class="_"> </span><span class="fc2 sc0">of</span><span class="_ _e"> </span><span class="fc2 sc0">the</span><span class="_"> </span><span class="fc2 sc0">ex</span><span class="fc2 sc0">p</span><span class="_ _a"></span><span class="fc2 sc0">erimen</span><span class="fc2 sc0">ts</span><span class="fc2 sc0">,</span><span class="_"> </span><span class="fc2 sc0">while</span><span class="_"> </span><span class="fc2 sc0">still</span></div><div class="t m0 x7 h5 y1f ff5 fs3 fc0 sc0 ls0 ws0"><span class="fc2 sc0">running</span><span class="_ _c"> </span><span class="fc2 sc0">in</span><span class="_"> </span><span class="fc2 sc0">real-time.</span><span class="_ _d"> </span>An<span class="_"> </span>open<span class="_ _c"> </span>source<span class="_"> </span>v<span class="_ _1"></span>ersion<span class="_ _c"> </span>of<span class="_"> </span>the</div><div class="t m0 x7 h5 y20 ff5 fs3 fc0 sc0 ls0 ws0">PL-SLAM<span class="_ _6"> </span>C++<span class="_ _6"> </span>code<span class="_ _6"> </span>will<span class="_ _6"> </span>b<span class="_ _a"></span>e<span class="_ _6"> </span>released<span class="_ _6"> </span>for<span class="_ _6"> </span>the<span class="_ _6"> </span>b<span class="_ _a"></span>enefit</div><div class="t m0 x7 h5 y21 ff5 fs3 fc0 sc0 ls0 ws0">of<span class="_ _9"> </span>the<span class="_ _8"> </span>communit<span class="_ _1"></span>y<span class="_ _4"></span>.</div><div class="t m0 x6 h5 y22 ff4 fs3 fc0 sc0 ls0 ws0">Index<span class="_ _b"> </span>T<span class="_ _4"></span>erms<span class="_ _a"></span><span class="ff5">—Stereo<span class="_ _b"> </span>Visual<span class="_ _0"> </span>SLAM,<span class="_ _b"> </span>line<span class="_ _b"> </span>segment</span></div><div class="t m0 x7 h5 y23 ff5 fs3 fc0 sc0 ls0 ws0">features,<span class="_ _9"> </span>bundle<span class="_ _8"> </span>adjustment,<span class="_ _8"> </span>lo<span class="_ _a"></span>op<span class="_ _9"> </span>closure</div><div class="t m0 x8 h6 y24 ff6 fs4 fc0 sc0 ls0 ws0">I.<span class="_ _e"> </span>Intr<span class="_ _1"></span>oduction</div><div class="t m0 x6 h6 y25 ff7 fs4 fc0 sc0 ls0 ws0">In<span class="_ _6"> </span>recent<span class="_ _6"> </span>y<span class="_ _1"></span>ears,<span class="_ _6"> </span>visual<span class="_ _6"> </span>Simultaneous<span class="_ _6"> </span>Localization<span class="_ _6"> </span>And</div><div class="t m0 x7 h6 y26 ff7 fs4 fc0 sc0 ls0 ws0">Mapping<span class="_ _7"> </span>(SLAM)<span class="_ _8"> </span>is<span class="_ _7"> </span>firmly<span class="_ _8"> </span>progressing<span class="_ _7"> </span>to<span class="_ _1"></span>wards<span class="_ _7"> </span>the<span class="_ _8"> </span>degree</div><div class="t m0 x7 h6 y27 ff7 fs4 fc0 sc0 ls0 ws0">of<span class="_ _10"> </span>reliability<span class="_ _10"> </span>required<span class="_ _10"> </span>for<span class="_ _10"> </span>fully<span class="_ _10"> </span>autonomous<span class="_ _7"> </span>v<span class="_ _1"></span>ehicles:<span class="_ _7"> </span>mobile</div><div class="t m0 x7 h6 y28 ff7 fs4 fc0 sc0 ls0 ws0">rob<span class="_ _a"></span>ots,<span class="_ _0"> </span>self-driving<span class="_ _0"> </span>cars<span class="_ _0"> </span>or<span class="_ _0"> </span>Unmanned<span class="_ _0"> </span>Aerial<span class="_ _b"> </span>V<span class="_ _4"></span>ehicles</div><div class="t m0 x7 h6 y29 ff7 fs4 fc0 sc0 ls0 ws0">(UA<span class="_ _4"></span>V<span class="_ _4"></span>s).<span class="_ _9"> </span>In<span class="_ _9"> </span>a<span class="_ _9"> </span>nutshell,<span class="_ _9"> </span>the<span class="_ _9"> </span>SLAM<span class="_ _9"> </span>problem<span class="_ _9"> </span>consists<span class="_ _9"> </span>of<span class="_ _9"> </span>the</div><div class="t m0 x7 h6 y2a ff7 fs4 fc0 sc0 ls0 ws0">estimation<span class="_ _8"> </span>of<span class="_ _8"> </span>the<span class="_ _8"> </span>vehicle<span class="_ _8"> </span>trajectory<span class="_ _9"> </span>giv<span class="_ _1"></span>en<span class="_ _8"> </span>as<span class="_ _8"> </span>a<span class="_ _9"> </span>set<span class="_ _8"> </span>of<span class="_ _8"> </span>poses</div><div class="t m0 x7 h6 y2b ff7 fs4 fc0 sc0 ls0 ws0">(p<span class="_ _a"></span>osition<span class="_ _3"> </span>and<span class="_ _6"> </span>orien<span class="_ _1"></span>tation),<span class="_ _6"> </span>while<span class="_ _3"> </span>simultaneously<span class="_ _3"> </span>building</div><div class="t m0 x7 h6 y2c ff7 fs4 fc0 sc0 ls0 ws0">a<span class="_ _9"> </span>map<span class="_ _9"> </span>of<span class="_ _9"> </span>the<span class="_ _9"> </span>en<span class="_ _1"></span>vironment.<span class="_ _8"> </span>Apart<span class="_ _9"> </span>from<span class="_ _9"> </span>self-lo<span class="_ _a"></span>calization,<span class="_ _9"> </span>a</div><div class="t m0 x7 h6 y2d ff7 fs4 fc0 sc0 ls0 ws0">map<span class="_ _9"> </span>b<span class="_ _a"></span>ecomes<span class="_ _3"> </span>useful<span class="_ _3"> </span>for<span class="_ _9"> </span>obstacle<span class="_ _3"> </span>av<span class="_ _1"></span>oidance,<span class="_ _3"> </span>ob<span class="_ _a"></span>ject<span class="_ _9"> </span>recog-</div><div class="t m0 x7 h6 y2e ff7 fs4 fc0 sc0 ls0 ws0">nition,<span class="_ _9"> </span>task<span class="_ _9"> </span>planning,<span class="_ _9"> </span>etc.<span class="_ _9"> </span>[1].</div><div class="t m0 x6 h6 y2f ff7 fs4 fc0 sc0 ls0 ws0">As<span class="_ _9"> </span>a<span class="_ _9"> </span>first-lev<span class="_ _f"></span>el<span class="_ _9"> </span>classification,<span class="_ _9"> </span>SLAM<span class="_ _9"> </span>systems<span class="_ _9"> </span>can<span class="_ _9"> </span>b<span class="_ _a"></span>e<span class="_ _9"> </span>di-</div><div class="t m0 x7 h6 y30 ff7 fs4 fc0 sc0 ls0 ws0">vided<span class="_ _8"> </span>in<span class="_ _1"></span>to<span class="_ _8"> </span><span class="ff8">top<span class="_ _1"></span>olo<span class="_ _1"></span>gic<span class="_ _f"></span>al<span class="_ _3"> </span><span class="ff7">(e.g.<span class="_ _8"> </span>[2]–[5])<span class="_ _8"> </span>and<span class="_ _8"> </span></span>metric<span class="_ _9"> </span><span class="ff7">approac<span class="_ _1"></span>hes.</span></span></div><div class="t m0 x9 h7 y31 ff9 fs5 fc0 sc0 ls0 ws0">This<span class="_ _11"> </span>work<span class="_ _11"> </span>has<span class="_ _11"> </span>been<span class="_ _11"> </span>supported<span class="_ _11"> </span>by<span class="_ _11"> </span>the<span class="_ _11"> </span>Spanish<span class="_ _11"> </span>Go<span class="_ _f"></span>vernmen<span class="_ _1"></span>t<span class="_ _11"> </span>(pro<span class="_ _a"></span>ject</div><div class="t m0 x7 h7 y32 ff9 fs5 fc0 sc0 ls0 ws0">DPI2017-84827-R<span class="_ _8"> </span>and<span class="_ _7"> </span>grant<span class="_ _8"> </span>BES-2015-071606)<span class="_ _7"> </span>and<span class="_ _8"> </span>the<span class="_ _8"> </span>Andalusian</div><div class="t m0 x7 h7 y33 ff9 fs5 fc0 sc0 ls0 ws0">Gov<span class="_ _1"></span>ernment<span class="_ _7"> </span>(project<span class="_ _8"> </span>TEP2012-530).</div><div class="t m0 x9 h7 y34 ff9 fs5 fc0 sc0 ls0 ws0">R.<span class="_ _7"> </span>Gomez-Ojeda,<span class="_ _7"> </span>F.A.<span class="_ _7"> </span>Moreno,<span class="_ _8"> </span>D.<span class="_ _10"> </span>Zuñiga-No<span class="_ _a"></span>ël,<span class="_ _7"> </span>and<span class="_ _8"> </span>J.<span class="_ _10"> </span>Gonzalez-</div><div class="t m0 x7 h7 y35 ff9 fs5 fc0 sc0 ls0 ws0">Jimenez<span class="_ _12"> </span>are<span class="_ _12"> </span>with<span class="_ _12"> </span>the<span class="_ _12"> </span>Machine<span class="_ _12"> </span>P<span class="_ _1"></span>erception<span class="_ _12"> </span>and<span class="_ _12"> </span>Intelligen<span class="_ _1"></span>t</div><div class="t m0 x7 h7 y36 ff9 fs5 fc0 sc0 ls0 ws0">Robotics<span class="_ _13"> </span>(MAPIR)<span class="_ _13"> </span>Group,<span class="_ _14"> </span>Universit<span class="_ _1"></span>y<span class="_ _13"> </span>of<span class="_ _14"> </span>Malaga.<span class="_ _13"> </span>(email:</div><div class="t m0 x7 h7 y37 ff9 fs5 fc0 sc0 ls0 ws0">rubengo<span class="_ _a"></span>o<span class="_ _a"></span>j@gmail.com).</div><div class="t m0 x9 h7 y38 ff9 fs5 fc0 sc0 ls0 ws0">D.<span class="_ _8"> </span>Scaram<span class="_ _f"></span>uzza<span class="_ _8"> </span>is<span class="_ _8"> </span>with<span class="_ _8"> </span>the<span class="_ _8"> </span>Robotics<span class="_ _8"> </span>and<span class="_ _8"> </span>Perception<span class="_ _8"> </span>Group,<span class="_ _8"> </span>Dep.</div><div class="t m0 x7 h7 y39 ff9 fs5 fc0 sc0 ls0 ws0">of<span class="_ _8"> </span>Informatics,<span class="_ _8"> </span>Universit<span class="_ _1"></span>y<span class="_ _9"> </span>of<span class="_ _8"> </span>Zuric<span class="_ _f"></span>h,<span class="_ _8"> </span>and<span class="_ _8"> </span>Dep.<span class="_ _8"> </span>of<span class="_ _9"> </span>Neuroinformatics,</div><div class="t m0 x7 h7 y3a ff9 fs5 fc0 sc0 ls0 ws0">Universit<span class="_ _1"></span>y<span class="_ _7"> </span>of<span class="_ _8"> </span>Zuric<span class="_ _1"></span>h<span class="_ _8"> </span>and<span class="_ _7"> </span>ETH<span class="_ _7"> </span>Zurich,<span class="_ _7"> </span>Switzerland.</div><div class="t m0 xa h7 y3b ff9 fs5 fc0 sc0 ls0 ws0">(a)<span class="_ _8"> </span><span class="ffa">lt-easy<span class="_ _15"> </span></span>(b)<span class="_ _8"> </span><span class="ffa">euro<span class="_ _4"></span>c/V2-01-easy</span></div><div class="t m0 xb h7 y3c ff9 fs5 fc0 sc0 ls0 ws0">(c)<span class="_ _8"> </span><span class="ffa">euro<span class="_ _4"></span>c/V1-01-easy<span class="_ _16"> </span><span class="ff9">(d)<span class="_ _8"> </span>Map<span class="_ _8"> </span>from<span class="_ _7"> </span>(c)</span></span></div><div class="t m0 xc h7 y3d ff9 fs5 fc0 sc0 ls0 ws0">Figure<span class="_ _9"> </span>1.<span class="_ _17"> </span>Low-textured<span class="_ _8"> </span>environmen<span class="_ _1"></span>ts<span class="_ _9"> </span>are<span class="_ _9"> </span>challenging<span class="_ _8"> </span>for<span class="_ _9"> </span><span class="ffa">fe<span class="_ _1"></span>ature-</span></div><div class="t m0 xc h7 y3e ffa fs5 fc0 sc0 ls0 ws0">b<span class="_ _1"></span>ase<span class="_ _1"></span>d<span class="_ _d"> </span><span class="ff9">SLAM<span class="_"> </span>systems<span class="_"> </span>based<span class="_ _3"> </span>on<span class="_"> </span>traditional<span class="_ _3"> </span>keypoints.<span class="_ _3"> </span>In<span class="_"> </span>con<span class="_ _1"></span>trast,</span></div><div class="t m0 xc h7 y3f ff9 fs5 fc0 sc0 ls0 ws0">line<span class="_"> </span>segments<span class="_"> </span>are<span class="_"> </span>usually<span class="_"> </span>common<span class="_"> </span>in<span class="_"> </span>h<span class="_ _1"></span>uman-made<span class="_"> </span>environmen<span class="_ _1"></span>ts,</div><div class="t m0 xc h7 y40 ff9 fs5 fc0 sc0 ls0 ws0">and<span class="_ _7"> </span>apart<span class="_ _7"> </span>from<span class="_ _7"> </span>an<span class="_ _7"> </span>improv<span class="_ _1"></span>ed<span class="_ _8"> </span>camera<span class="_ _10"> </span>lo<span class="_ _a"></span>calization,<span class="_ _7"> </span>the<span class="_ _7"> </span>built<span class="_ _7"> </span>maps<span class="_ _8"> </span>are</div><div class="t m0 xc h7 y41 ff9 fs5 fc0 sc0 ls0 ws0">richer<span class="_ _11"> </span>as<span class="_ _11"> </span>they<span class="_ _11"> </span>are<span class="_ _11"> </span>p<span class="_ _a"></span>opulated<span class="_ _11"> </span>with<span class="_ _11"> </span>more<span class="_ _10"> </span>meaningful<span class="_ _11"> </span>elements<span class="_ _11"> </span>(3D<span class="_ _11"> </span>line-</div><div class="t m0 xc h7 y42 ff9 fs5 fc0 sc0 ls0 ws0">segments).</div><div class="t m0 xc h6 y43 ff7 fs4 fc0 sc0 ls0 ws0">In<span class="_ _e"> </span>this<span class="_"> </span>pap<span class="_ _a"></span>er,<span class="_ _e"> </span>w<span class="_ _1"></span>e<span class="_ _e"> </span>fo<span class="_ _a"></span>cus<span class="_ _e"> </span>on<span class="_"> </span>the<span class="_ _e"> </span>latter,<span class="_ _18"> </span>whic<span class="_ _1"></span>h<span class="_ _e"> </span>take<span class="_"> </span>into</div><div class="t m0 xc h6 y44 ff7 fs4 fc0 sc0 ls0 ws0">accoun<span class="_ _1"></span>t<span class="_ _8"> </span>the<span class="_ _7"> </span><span class="ff8">ge<span class="_ _1"></span>ometric<span class="_ _8"> </span><span class="ff7">information<span class="_ _7"> </span>of<span class="_ _7"> </span>the<span class="_ _8"> </span>en<span class="_ _1"></span>vironment<span class="_ _10"> </span>and</span></span></div><div class="t m0 xc h6 y45 ff7 fs4 fc0 sc0 ls0 ws0">build<span class="_ _18"> </span>a<span class="_ _18"> </span>ph<span class="_ _1"></span>ysically<span class="_ _18"> </span>meaningful<span class="_ _18"> </span>map<span class="_ _18"> </span>of<span class="_ _18"> </span>it<span class="_ _18"> </span>[6],<span class="_ _18"> </span>[7].<span class="_"> </span>These</div><div class="t m0 xc h6 y46 ff7 fs4 fc0 sc0 ls0 ws0">approac<span class="_ _1"></span>hes<span class="_ _7"> </span>can<span class="_ _10"> </span>b<span class="_ _a"></span>e<span class="_ _10"> </span>further<span class="_ _7"> </span>classified<span class="_ _10"> </span>in<span class="_ _f"></span>to<span class="_ _10"> </span><span class="ff8">dir<span class="_ _1"></span>e<span class="_ _1"></span>ct<span class="_ _8"> </span><span class="ff7">and<span class="_ _10"> </span></span>fe<span class="_ _1"></span>atur<span class="_ _1"></span>e-</span></div><div class="t m0 xc h6 y47 ff8 fs4 fc0 sc0 ls0 ws0">b<span class="_ _1"></span>ase<span class="_ _1"></span>d<span class="_ _19"> </span><span class="ff7">systems.<span class="_ _6"> </span>The<span class="_ _6"> </span>first<span class="_ _6"> </span>group,<span class="_ _6"> </span>i.e.<span class="_ _6"> </span></span>dir<span class="_ _1"></span>e<span class="_ _1"></span>ct<span class="_ _c"> </span><span class="ff7">metho<span class="_ _a"></span>ds,<span class="_ _6"> </span>esti-</span></div><div class="t m0 xc h6 y48 ff7 fs4 fc0 sc0 ls0 ws0">mates<span class="_ _9"> </span>the<span class="_ _9"> </span>camera<span class="_ _9"> </span>motion<span class="_ _3"> </span>b<span class="_ _1"></span>y<span class="_ _3"> </span>minimizing<span class="_ _9"> </span>the<span class="_ _9"> </span>photometric</div><div class="t m0 xc h6 y49 ff7 fs4 fc0 sc0 ls0 ws0">errors<span class="_ _10"> </span>b<span class="_ _a"></span>etw<span class="_ _1"></span>een<span class="_ _10"> </span>consecutive<span class="_ _10"> </span>frames<span class="_ _10"> </span>under<span class="_ _10"> </span>the<span class="_ _10"> </span>assumption<span class="_ _10"> </span>of</div><div class="t m0 xc h6 y4a ff7 fs4 fc0 sc0 ls0 ws0">constan<span class="_ _1"></span>t<span class="_ _9"> </span>brightness<span class="_ _8"> </span>along<span class="_ _9"> </span>the<span class="_ _8"> </span>lo<span class="_ _a"></span>cal<span class="_ _9"> </span>parts<span class="_ _8"> </span>of<span class="_ _9"> </span>the<span class="_ _9"> </span>sequences</div><div class="t m0 xc h6 y4b ff7 fs4 fc0 sc0 ls0 ws0">(examples<span class="_ _d"> </span>of<span class="_"> </span>this<span class="_ _6"> </span>approach<span class="_ _d"> </span>can<span class="_"> </span>be<span class="_"> </span>found<span class="_ _6"> </span>elsewhere<span class="_"> </span>[8]–</div><div class="t m0 xc h6 y4c ff7 fs4 fc0 sc0 ls0 ws0">[10]).<span class="_ _d"> </span>While<span class="_ _d"> </span>this<span class="_ _d"> </span>group<span class="_ _d"> </span>of<span class="_ _d"> </span>techniques<span class="_ _6"> </span>has<span class="_"> </span>the<span class="_ _6"> </span>adv<span class="_ _1"></span>antage</div><div class="t m0 xc h6 y4d ff7 fs4 fc0 sc0 ls0 ws0">of<span class="_"> </span>w<span class="_ _1"></span>orking<span class="_"> </span>directly<span class="_"> </span>with<span class="_"> </span>the<span class="_"> </span>input<span class="_ _d"> </span>images<span class="_"> </span>regardless<span class="_"> </span>of</div><div class="t m0 xc h6 y4e ff7 fs4 fc0 sc0 ls0 ws0">an<span class="_ _1"></span>y<span class="_ _8"> </span>in<span class="_ _1"></span>termediate<span class="_ _8"> </span>represen<span class="_ _1"></span>tation,<span class="_ _8"> </span>they<span class="_ _7"> </span>are<span class="_ _8"> </span>v<span class="_ _1"></span>ery<span class="_ _8"> </span>sensitiv<span class="_ _1"></span>e<span class="_ _8"> </span>to</div><div class="t m0 xc h6 y4f ff7 fs4 fc0 sc0 ls0 ws0">brigh<span class="_ _1"></span>tness<span class="_ _7"> </span>changes<span class="_ _7"> </span>(this<span class="_ _7"> </span>phenomena<span class="_ _10"> </span>was<span class="_ _7"> </span>addressed<span class="_ _7"> </span>in<span class="_ _7"> </span>[11])</div><div class="t m0 xc h6 y50 ff7 fs4 fc0 sc0 ls0 ws0">and<span class="_ _9"> </span>constrained<span class="_ _8"> </span>to<span class="_ _9"> </span>narrow<span class="_ _8"> </span>baseline<span class="_ _9"> </span>motions.<span class="_ _1a"> </span>In<span class="_ _9"> </span>con<span class="_ _1"></span>trast,</div><div class="t m0 xc h6 y51 ff8 fs4 fc0 sc0 ls0 ws0">fe<span class="_ _1"></span>atur<span class="_ _1"></span>e-b<span class="_ _1"></span>ase<span class="_ _1"></span>d<span class="_ _19"> </span><span class="ff7">metho<span class="_ _a"></span>ds<span class="_ _6"> </span>employ<span class="_ _6"> </span>an<span class="_ _6"> </span>indirect<span class="_ _6"> </span>representation</span></div><div class="t m0 xc h6 y52 ff7 fs4 fc0 sc0 ls0 ws0">of<span class="_ _8"> </span>the<span class="_ _8"> </span>images,<span class="_ _8"> </span>typically<span class="_ _8"> </span>in<span class="_ _8"> </span>the<span class="_ _8"> </span>form<span class="_ _8"> </span>of<span class="_ _8"> </span>p<span class="_ _a"></span>oint<span class="_ _8"> </span>features,<span class="_ _8"> </span>that</div><div class="t m0 xc h6 y53 ff7 fs4 fc0 sc0 ls0 ws0">are<span class="_ _7"> </span>track<span class="_ _1"></span>ed<span class="_ _7"> </span>along<span class="_ _7"> </span>the<span class="_ _7"> </span>successive<span class="_ _10"> </span>frames<span class="_ _7"> </span>and<span class="_ _7"> </span>then<span class="_ _7"> </span>employ<span class="_ _1"></span>ed</div><div class="t m0 xc h6 y54 ff7 fs4 fc0 sc0 ls0 ws0">for<span class="_ _7"> </span>reco<span class="_ _1"></span>vering<span class="_ _10"> </span>the<span class="_ _7"> </span>p<span class="_ _a"></span>ose<span class="_ _7"> </span>by<span class="_ _10"> </span>minimizing<span class="_ _7"> </span>the<span class="_ _7"> </span>pro<span class="_ _a"></span>jection<span class="_ _7"> </span>errors</div><div class="t m0 xc h6 y55 ff7 fs4 fc0 sc0 ls0 ws0">[12],<span class="_ _9"> </span>[13].</div><div class="t m0 xd h6 y56 ff7 fs4 fc0 sc0 ls0 ws0">It<span class="_ _10"> </span>is<span class="_ _10"> </span>noticeable<span class="_ _10"> </span>that<span class="_ _10"> </span>the<span class="_ _10"> </span>p<span class="_ _a"></span>erformance<span class="_ _7"> </span>of<span class="_ _10"> </span>an<span class="_ _f"></span>y<span class="_ _10"> </span>of<span class="_ _10"> </span>the<span class="_ _10"> </span>ab<span class="_ _a"></span>ov<span class="_ _1"></span>e-</div><div class="t m0 xc h6 y57 ff7 fs4 fc0 sc0 ls0 ws0">men<span class="_ _1"></span>tioned<span class="_"> </span>approaches<span class="_ _d"> </span>usually<span class="_"> </span>decreases<span class="_"> </span>in<span class="_ _d"> </span>lo<span class="_ _f"></span>w-textured</div><div class="t m0 xc h6 y58 ff7 fs4 fc0 sc0 ls0 ws0">en<span class="_ _1"></span>vironments<span class="_"> </span>in<span class="_"> </span>which<span class="_"> </span>it<span class="_"> </span>is<span class="_"> </span>t<span class="_ _1"></span>ypically<span class="_ _19"> </span>difficult<span class="_"> </span>to<span class="_ _19"> </span>find<span class="_"> </span>a</div><div class="t m0 xc h6 y59 ff7 fs4 fc0 sc0 ls0 ws0">large<span class="_ _3"> </span>set<span class="_ _3"> </span>of<span class="_ _6"> </span>k<span class="_ _1"></span>eyp<span class="_ _a"></span>oint<span class="_ _3"> </span>features.<span class="_ _3"> </span>The<span class="_ _3"> </span>effect<span class="_ _6"> </span>in<span class="_ _3"> </span>suc<span class="_ _f"></span>h<span class="_ _3"> </span>cases<span class="_ _3"> </span>is</div><div class="t m0 xc h6 y5a ff7 fs4 fc0 sc0 ls0 ws0">an<span class="_ _6"> </span>accuracy<span class="_ _6"> </span>imp<span class="_ _a"></span>ov<span class="_ _1"></span>erishment<span class="_ _6"> </span>and,<span class="_ _6"> </span>occasionally<span class="_ _4"></span>,<span class="_ _6"> </span>the<span class="_ _6"> </span>com-</div><div class="t m0 xc h6 y3a ff7 fs4 fc0 sc0 ls0 ws0">plete<span class="_"> </span>failure<span class="_ _18"> </span>of<span class="_ _19"> </span>the<span class="_ _18"> </span>system.<span class="_ _19"> </span>Many<span class="_"> </span>of<span class="_ _18"> </span>such<span class="_"> </span>lo<span class="_ _f"></span>w-textured</div><div class="t m1 xe h8 y5b ffb fs6 fc1 sc0 ls0 ws0">arXiv:1705.09479v2 [cs.CV] 9 Apr 2018</div><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a></div><div class="pi" data-data='{"ctm":[1.568627,0.000000,0.000000,1.568627,0.000000,0.000000]}'></div></div><div id="pf2" class="pf w0 h0" data-page-no="2"><div class="pc pc2 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="/image.php?url=https://csdnimg.cn/release/download_crawler_static/89541504/bg2.jpg"><div class="t m0 x1 h2 y1 ff1 fs0 fc0 sc0 ls0 ws0">2</div><div class="t m0 x7 h6 y5c ff7 fs4 fc0 sc0 ls0 ws0">en<span class="_ _1"></span>vironments,<span class="_ _3"> </span>how<span class="_ _1"></span>ever,<span class="_ _3"> </span>contain<span class="_ _3"> </span>planar<span class="_ _3"> </span>elements<span class="_ _3"> </span>that<span class="_ _6"> </span>are</div><div class="t m0 x7 h6 y5d ff7 fs4 fc0 sc0 ls0 ws0">ric<span class="_ _1"></span>h<span class="_"> </span>in<span class="_ _6"> </span>linear<span class="_ _d"> </span>shap<span class="_ _a"></span>es,<span class="_ _d"> </span>so<span class="_ _d"> </span>it<span class="_ _d"> </span>w<span class="_ _f"></span>ould<span class="_ _6"> </span>b<span class="_ _2"></span>e<span class="_ _6"> </span>p<span class="_ _2"></span>ossible<span class="_ _6"> </span>to<span class="_"> </span>extract</div><div class="t m0 x7 h6 y5e ff7 fs4 fc0 sc0 ls0 ws0">line<span class="_ _7"> </span>segments<span class="_ _10"> </span>from<span class="_ _8"> </span>them.<span class="_ _10"> </span>W<span class="_ _1"></span>e<span class="_ _7"> </span>claim<span class="_ _7"> </span>that<span class="_ _7"> </span>these<span class="_ _7"> </span>tw<span class="_ _1"></span>o<span class="_ _8"> </span>t<span class="_ _1"></span>yp<span class="_ _a"></span>es<span class="_ _7"> </span>of</div><div class="t m0 x7 h6 y5f ff7 fs4 fc0 sc0 ls0 ws0">features<span class="_ _8"> </span>(k<span class="_ _1"></span>eyp<span class="_ _2"></span>oin<span class="_ _1"></span>ts<span class="_ _8"> </span>and<span class="_ _8"> </span>segments)<span class="_ _8"> </span>complemen<span class="_ _1"></span>t<span class="_ _8"> </span>each<span class="_ _8"> </span>other</div><div class="t m0 x7 h6 y60 ff7 fs4 fc0 sc0 ls0 ws0">and<span class="_ _9"> </span>its<span class="_ _9"> </span>com<span class="_ _1"></span>bination<span class="_ _9"> </span>leads<span class="_ _9"> </span>to<span class="_ _9"> </span>a<span class="_ _9"> </span>more<span class="_ _9"> </span>v<span class="_ _1"></span>ersatile,<span class="_ _9"> </span>robust<span class="_ _9"> </span>and</div><div class="t m0 x7 h6 y61 ff7 fs4 fc0 sc0 ls0 ws0">stable<span class="_ _18"> </span>SLAM<span class="_ _e"> </span>system.<span class="_ _e"> </span>F<span class="_ _4"></span>urthermore,<span class="_ _e"> </span>the<span class="_ _e"> </span>resulting<span class="_ _e"> </span>maps</div><div class="t m0 x7 h6 y62 ff7 fs4 fc0 sc0 ls0 ws0">comprising<span class="_"> </span>b<span class="_ _a"></span>oth<span class="_"> </span>3D<span class="_ _19"> </span>p<span class="_ _2"></span>oin<span class="_ _1"></span>ts<span class="_ _19"> </span>and<span class="_ _18"> </span>segmen<span class="_ _f"></span>ts<span class="_"> </span>provide<span class="_"> </span>more</div><div class="t m0 x7 h6 y63 ff7 fs4 fc0 sc0 ls0 ws0">structural<span class="_ _3"> </span>information<span class="_ _3"> </span>from<span class="_ _6"> </span>the<span class="_ _3"> </span>en<span class="_ _1"></span>vironment<span class="_ _3"> </span>than<span class="_ _3"> </span>p<span class="_ _a"></span>oint-</div><div class="t m0 x7 h6 y64 ff7 fs4 fc0 sc0 ls0 ws0">only<span class="_ _8"> </span>maps,<span class="_ _8"> </span>as<span class="_ _8"> </span>can<span class="_ _7"> </span>b<span class="_ _a"></span>e<span class="_ _8"> </span>seen<span class="_ _8"> </span>in<span class="_ _8"> </span>the<span class="_ _8"> </span>example<span class="_ _8"> </span>sho<span class="_ _1"></span>wn<span class="_ _8"> </span>in<span class="_ _8"> </span>Figure</div><div class="t m0 x7 h6 y65 ff7 fs4 fc0 sc0 ls0 ws0">1(d).<span class="_ _10"> </span>Thus,<span class="_ _10"> </span>applications<span class="_ _7"> </span>that<span class="_ _7"> </span>p<span class="_ _a"></span>erform<span class="_ _7"> </span>high-lev<span class="_ _f"></span>el<span class="_ _10"> </span>tasks<span class="_ _7"> </span>such</div><div class="t m0 x7 h6 y6 ff7 fs4 fc0 sc0 ls0 ws0">as<span class="_ _9"> </span>place<span class="_ _3"> </span>recognition,<span class="_ _3"> </span>seman<span class="_ _1"></span>tic<span class="_ _3"> </span>mapping<span class="_ _3"> </span>or<span class="_ _9"> </span>task<span class="_ _3"> </span>planning,</div><div class="t m0 x7 h6 y66 ff7 fs4 fc0 sc0 ls0 ws0">among<span class="_ _18"> </span>others,<span class="_ _18"> </span>can<span class="_ _18"> </span>signi&#64257;cantly<span class="_"> </span>b<span class="_ _a"></span>ene&#64257;t<span class="_ _18"> </span>from<span class="_ _e"> </span>the<span class="_ _18"> </span>richer</div><div class="t m0 x7 h6 y67 ff7 fs4 fc0 sc0 ls0 ws0">information<span class="_ _9"> </span>that<span class="_ _9"> </span>can<span class="_ _9"> </span>be<span class="_ _9"> </span>inferred<span class="_ _9"> </span>from<span class="_ _9"> </span>them.</div><div class="t m0 x6 h6 y68 ff7 fs4 fc0 sc0 ls0 ws0">These<span class="_ _8"> </span>bene&#64257;ts,<span class="_ _8"> </span>though,<span class="_ _8"> </span>come<span class="_ _8"> </span>at<span class="_ _8"> </span>the<span class="_ _8"> </span>expense<span class="_ _8"> </span>of<span class="_ _8"> </span>a<span class="_ _8"> </span>higher</div><div class="t m0 x7 h6 y69 ff7 fs4 fc0 sc0 ls0 ws0">computational<span class="_ _e"> </span>burden<span class="_ _e"> </span>in<span class="_ _e"> </span>b<span class="_ _a"></span>oth<span class="_ _e"> </span>detecting<span class="_ _e"> </span>and<span class="_ _e"> </span>matching</div><div class="t m0 x7 h6 y6a ff7 fs4 fc0 sc0 ls0 ws0">line-segmen<span class="_ _1"></span>ts<span class="_ _8"> </span>in<span class="_ _7"> </span>images<span class="_ _7"> </span>[14],<span class="_ _7"> </span>and<span class="_ _8"> </span>also<span class="_ _7"> </span>in<span class="_ _7"> </span>dealing<span class="_ _7"> </span>e&#64256;ectively</div><div class="t m0 x7 h6 y6b ff7 fs4 fc0 sc0 ls0 ws0">with<span class="_ _7"> </span>segment-speci&#64257;c<span class="_ _8"> </span>problems<span class="_ _7"> </span>like<span class="_ _7"> </span>partial<span class="_ _7"> </span>o<span class="_ _a"></span>cclusions,<span class="_ _8"> </span>line</div><div class="t m0 x7 h6 y6c ff7 fs4 fc0 sc0 ls0 ws0">disconnection,<span class="_ _9"> </span>etc.<span class="_ _9"> </span>whic<span class="_ _1"></span>h<span class="_ _9"> </span>complicate<span class="_ _9"> </span>feature<span class="_ _9"> </span>trac<span class="_ _1"></span>king<span class="_ _9"> </span>and</div><div class="t m0 x7 h6 y6d ff7 fs4 fc0 sc0 ls0 ws0">matc<span class="_ _1"></span>hing<span class="_ _9"> </span>as<span class="_ _8"> </span>well<span class="_ _8"> </span>as<span class="_ _8"> </span>the<span class="_ _9"> </span>residual<span class="_ _8"> </span>computation<span class="_ _8"> </span>for<span class="_ _9"> </span>the<span class="_ _8"> </span>map</div><div class="t m0 x7 h6 y6e ff7 fs4 fc0 sc0 ls0 ws0">and<span class="_ _6"> </span>pose<span class="_ _6"> </span>optimization.<span class="_ _6"> </span>Suc<span class="_ _1"></span>h<span class="_ _6"> </span>hurdles<span class="_ _3"> </span>are<span class="_ _6"> </span>the<span class="_ _6"> </span>reason<span class="_ _6"> </span>wh<span class="_ _1"></span>y</div><div class="t m0 x7 h6 y6f ff7 fs4 fc0 sc0 ls0 ws0">the<span class="_ _6"> </span>n<span class="_ _1"></span>umber<span class="_ _6"> </span>of<span class="_ _6"> </span>solutions<span class="_ _6"> </span>that<span class="_ _6"> </span>hav<span class="_ _1"></span>e<span class="_ _6"> </span>b<span class="_ _a"></span>een<span class="_ _6"> </span>prop<span class="_ _2"></span>osed<span class="_ _6"> </span>in<span class="_ _6"> </span>the</div><div class="t m0 x7 h6 y70 ff7 fs4 fc0 sc0 ls0 ws0">literature<span class="_ _9"> </span>to<span class="_ _8"> </span>SLAM<span class="_ _9"> </span>or<span class="_ _9"> </span>Structure<span class="_ _8"> </span>from<span class="_ _9"> </span>Motion<span class="_ _9"> </span>(SfM)<span class="_ _8"> </span>with</div><div class="t m0 x7 h6 y71 ff7 fs4 fc0 sc0 ls0 ws0">line<span class="_ _e"> </span>features<span class="_ _e"> </span>(e.g.<span class="_ _b"> </span>[15]&#8211;[19])<span class="_ _18"> </span>is<span class="_ _b"> </span>so<span class="_ _18"> </span>limited.<span class="_ _b"> </span>Besides,<span class="_ _18"> </span>the</div><div class="t m0 x7 h6 y72 ff7 fs4 fc0 sc0 ls0 ws0">few<span class="_ _e"> </span>solutions<span class="_ _e"> </span>we<span class="_ _e"> </span>hav<span class="_ _1"></span>e<span class="_ _e"> </span>found<span class="_ _e"> </span>only<span class="_ _b"> </span>perform<span class="_ _b"> </span>robustly<span class="_ _e"> </span>in</div><div class="t m0 x7 h6 y73 ff7 fs4 fc0 sc0 ls0 ws0">highly<span class="_ _6"> </span>structured<span class="_ _6"> </span>en<span class="_ _1"></span>vironments<span class="_ _6"> </span>while<span class="_ _6"> </span>sho<span class="_ _1"></span>wing<span class="_ _6"> </span>unreliable</div><div class="t m0 x7 h6 y74 ff7 fs4 fc0 sc0 ls0 ws0">results<span class="_ _3"> </span>when<span class="_ _3"> </span>applied<span class="_ _3"> </span>to<span class="_ _3"> </span>more<span class="_ _3"> </span>realistic<span class="_ _3"> </span>ones<span class="_ _3"> </span>suc<span class="_ _1"></span>h<span class="_ _3"> </span>as<span class="_ _3"> </span>those</div><div class="t m0 x7 h6 y75 ff7 fs4 fc0 sc0 ls0 ws0">recorded<span class="_ _3"> </span>in<span class="_ _3"> </span>the<span class="_ _3"> </span>KITTI<span class="_ _9"> </span>or<span class="_ _3"> </span>EuRoC<span class="_ _3"> </span>datasets.<span class="_ _3"> </span>In<span class="_ _3"> </span>this<span class="_ _3"> </span>work,</div><div class="t m0 x7 h6 y76 ff7 fs4 fc0 sc0 ls0 ws0">w<span class="_ _1"></span>e<span class="_ _e"> </span>address<span class="_ _18"> </span>the<span class="_ _18"> </span>segment-speci&#64257;c<span class="_ _18"> </span>tracking<span class="_"> </span>and<span class="_ _e"> </span>matching</div><div class="t m0 x7 h6 y77 ff7 fs4 fc0 sc0 ls0 ws0">issues<span class="_"> </span>b<span class="_ _1"></span>y<span class="_"> </span>discarding<span class="_"> </span>outliers<span class="_ _d"> </span>through<span class="_"> </span>the<span class="_"> </span>comparison<span class="_ _d"> </span>of</div><div class="t m0 x7 h6 y78 ff7 fs4 fc0 sc0 ls0 ws0">the<span class="_ _9"> </span>length<span class="_ _3"> </span>and<span class="_ _9"> </span>the<span class="_ _3"> </span>orien<span class="_ _f"></span>tation<span class="_ _9"> </span>of<span class="_ _3"> </span>the<span class="_ _9"> </span>line<span class="_ _3"> </span>features,<span class="_ _9"> </span>while,</div><div class="t m0 x7 h6 y79 ff7 fs4 fc0 sc0 ls0 ws0">for<span class="_ _7"> </span>the<span class="_ _7"> </span>residual<span class="_ _7"> </span>computation,<span class="_ _7"> </span>we<span class="_ _7"> </span>represen<span class="_ _f"></span>t<span class="_ _7"> </span>segments<span class="_ _10"> </span>in<span class="_ _7"> </span>the</div><div class="t m0 x7 h6 y7a ff7 fs4 fc0 sc0 ls0 ws0">map<span class="_ _8"> </span>with<span class="_ _8"> </span>their<span class="_ _8"> </span>endpoints<span class="_ _8"> </span>coordinates.<span class="_ _8"> </span>Thus,<span class="_ _8"> </span>the<span class="_ _8"> </span>residuals</div><div class="t m0 x7 h6 y7b ff7 fs4 fc0 sc0 ls0 ws0">b<span class="_ _a"></span>et<span class="_ _f"></span>w<span class="_ _1"></span>een<span class="_"> </span>the<span class="_ _d"> </span>observed<span class="_ _6"> </span>segments<span class="_ _6"> </span>and<span class="_"> </span>their<span class="_ _d"> </span>corresp<span class="_ _a"></span>onding</div><div class="t m0 x7 h6 y7c ff7 fs4 fc0 sc0 ls0 ws0">lines<span class="_ _7"> </span>in<span class="_ _10"> </span>the<span class="_ _7"> </span>map<span class="_ _7"> </span>are<span class="_ _7"> </span>computed<span class="_ _7"> </span>b<span class="_ _f"></span>y<span class="_ _7"> </span>the<span class="_ _10"> </span>distance<span class="_ _7"> </span>b<span class="_ _a"></span>etw<span class="_ _1"></span>een<span class="_ _7"> </span>the</div><div class="t m0 x7 h6 y7d ff7 fs4 fc0 sc0 ls0 ws0">pro<span class="_ _a"></span>jections<span class="_ _8"> </span>of<span class="_ _8"> </span>those<span class="_ _8"> </span>endpoints<span class="_ _8"> </span>on<span class="_ _8"> </span>the<span class="_ _7"> </span>image<span class="_ _8"> </span>plane<span class="_ _8"> </span>and<span class="_ _8"> </span>the</div><div class="t m0 x7 h6 y7e ff7 fs4 fc0 sc0 ls0 ws0">in&#64257;nite<span class="_ _7"> </span>lines<span class="_ _8"> </span>associated<span class="_ _8"> </span>to<span class="_ _7"> </span>the<span class="_ _8"> </span>observ<span class="_ _1"></span>ed<span class="_ _8"> </span>ones.<span class="_ _7"> </span>This<span class="_ _7"> </span>wa<span class="_ _1"></span>y<span class="_ _4"></span>,<span class="_ _8"> </span>w<span class="_ _1"></span>e</div><div class="t m0 x7 h6 y7f ff7 fs4 fc0 sc0 ls0 ws0">are<span class="_ _7"> </span>able<span class="_ _8"> </span>to<span class="_ _7"> </span>build<span class="_ _7"> </span>a<span class="_ _8"> </span>consisten<span class="_ _1"></span>t<span class="_ _8"> </span>cost<span class="_ _7"> </span>function<span class="_ _7"> </span>that<span class="_ _8"> </span>seamlessly</div><div class="t m0 x7 h6 y80 ff7 fs4 fc0 sc0 ls0 ws0">encompasses<span class="_ _9"> </span>both<span class="_ _9"> </span>p<span class="_ _a"></span>oint<span class="_ _9"> </span>and<span class="_ _9"> </span>line<span class="_ _9"> </span>features.</div><div class="t m0 x6 h6 y81 ff7 fs4 fc0 sc0 ls0 ws0">These<span class="_"> </span>t<span class="_ _1"></span>wo<span class="_ _d"> </span>kinds<span class="_"> </span>of<span class="_ _d"> </span>features<span class="_"> </span>are<span class="_ _d"> </span>also<span class="_"> </span>emplo<span class="_ _1"></span>yed<span class="_"> </span>to<span class="_ _d"> </span>ro-</div><div class="t m0 x7 h6 y82 ff7 fs4 fc0 sc0 ls0 ws0">bustly<span class="_ _6"> </span>detect<span class="_ _d"> </span>lo<span class="_ _a"></span>op<span class="_ _6"> </span>closures<span class="_ _d"> </span>during<span class="_ _d"> </span>rob<span class="_ _a"></span>ot<span class="_ _6"> </span>navigation,<span class="_ _6"> </span>fol-</div><div class="t m0 x7 h6 y83 ff7 fs4 fc0 sc0 ls0 ws0">lo<span class="_ _1"></span>wing<span class="_"> </span>a<span class="_"> </span>new<span class="_"> </span>bag-of-w<span class="_ _1"></span>ords<span class="_"> </span>approach<span class="_ _d"> </span>that<span class="_"> </span>combines<span class="_ _d"> </span>the</div><div class="t m0 x7 h6 y84 ff7 fs4 fc0 sc0 ls0 ws0">adv<span class="_ _1"></span>an<span class="_ _1"></span>tages<span class="_ _9"> </span>of<span class="_ _3"> </span>using<span class="_ _9"> </span>eac<span class="_ _1"></span>h<span class="_ _3"> </span>of<span class="_ _9"> </span>them<span class="_ _9"> </span>to<span class="_ _9"> </span>p<span class="_ _a"></span>erform<span class="_ _9"> </span>place<span class="_ _9"> </span>recog-</div><div class="t m0 x7 h6 y85 ff7 fs4 fc0 sc0 ls0 ws0">nition.<span class="_ _10"> </span>In<span class="_ _10"> </span>summary<span class="_ _4"></span>,<span class="_ _7"> </span>w<span class="_ _1"></span>e<span class="_ _7"> </span>propose<span class="_ _7"> </span>a<span class="_ _10"> </span>nov<span class="_ _1"></span>el<span class="_ _10"> </span>and<span class="_ _10"> </span>versatile<span class="_ _10"> </span>stereo</div><div class="t m0 x7 h6 y86 ff7 fs4 fc0 sc0 ls0 ws0">visual<span class="_ _10"> </span>SLAM<span class="_ _10"> </span>system,<span class="_ _10"> </span>coined<span class="_ _10"> </span>PL-SLAM,<span class="_ _7"> </span>whic<span class="_ _1"></span>h<span class="_ _7"> </span>builds<span class="_ _10"> </span>up<span class="_ _a"></span>on</div><div class="t m0 x7 h6 y87 ff7 fs4 fc0 sc0 ls0 ws0">our<span class="_ _8"> </span>previous<span class="_ _8"> </span>Visual<span class="_ _8"> </span>Odometry<span class="_ _7"> </span>approach<span class="_ _8"> </span>presen<span class="_ _1"></span>ted<span class="_ _8"> </span>in<span class="_ _8"> </span>[20],</div><div class="t m0 x7 h6 y88 ff7 fs4 fc0 sc0 ls0 ws0">and<span class="_ _18"> </span>comb<span class="_ _f"></span>ines<span class="_ _18"> </span>b<span class="_ _a"></span>oth<span class="_ _18"> </span>p<span class="_ _a"></span>oint<span class="_"> </span>and<span class="_ _18"> </span>line<span class="_ _18"> </span>segment<span class="_ _19"> </span>features<span class="_ _18"> </span>to</div><div class="t m0 x7 h6 y89 ff7 fs4 fc0 sc0 ls0 ws0">p<span class="_ _a"></span>erform<span class="_"> </span>real-time<span class="_ _18"> </span>rob<span class="_ _a"></span>ot<span class="_ _18"> </span>lo<span class="_ _a"></span>calization<span class="_ _19"> </span>and<span class="_ _18"> </span>mapping.<span class="_ _19"> </span>The</div><div class="t m0 x7 h6 y8a ff7 fs4 fc0 sc0 ls0 ws0">main<span class="_ _9"> </span>con<span class="_ _1"></span>tributions<span class="_ _9"> </span>of<span class="_ _9"> </span>this<span class="_ _9"> </span>work<span class="_ _8"> </span>are:</div><div class="t m0 x7 h9 y8b ffc fs4 fc0 sc0 ls0 ws0">&#9702;<span class="_ _c"> </span><span class="ff7">The<span class="_ _8"> </span>&#64257;rst<span class="_ _10"> </span>op<span class="_ _a"></span>en<span class="_ _8"> </span>source<span class="_ _7"> </span>stereo<span class="_ _7"> </span>SLAM<span class="_ _7"> </span>system<span class="_ _8"> </span>that<span class="_ _10"> </span>employs</span></div><div class="t m0 x6 h6 y8c ff7 fs4 fc0 sc0 ls0 ws0">p<span class="_ _a"></span>oin<span class="_ _f"></span>t<span class="_ _b"> </span>and<span class="_ _e"> </span>line<span class="_ _b"> </span>segmen<span class="_ _1"></span>t<span class="_ _b"> </span>features<span class="_ _b"> </span>in<span class="_ _e"> </span>real<span class="_ _b"> </span>time,<span class="_ _e"> </span>hence</div><div class="t m0 x6 h6 y8d ff7 fs4 fc0 sc0 ls0 ws0">b<span class="_ _a"></span>eing<span class="_ _b"> </span>capable<span class="_ _0"> </span>of<span class="_ _b"> </span>op<span class="_ _a"></span>erating<span class="_ _b"> </span>robustly<span class="_ _0"> </span>in<span class="_ _b"> </span>low-textured</div><div class="t m0 x6 h6 y32 ff7 fs4 fc0 sc0 ls0 ws0">en<span class="_ _1"></span>vironments<span class="_"> </span>where<span class="_ _d"> </span>traditional<span class="_"> </span>point-only<span class="_ _d"> </span>approaches</div><div class="t m0 x6 h6 y56 ff7 fs4 fc0 sc0 ls0 ws0">tend<span class="_ _18"> </span>to<span class="_ _18"> </span>fail,<span class="_ _e"> </span>while<span class="_ _18"> </span>obtaining<span class="_ _e"> </span>similar<span class="_ _18"> </span>accuracy<span class="_ _18"> </span>in<span class="_ _e"> </span>the</div><div class="t m0 x6 h6 y8e ff7 fs4 fc0 sc0 ls0 ws0">rest<span class="_"> </span>of<span class="_"> </span>the<span class="_ _d"> </span>scenarios.<span class="_"> </span>Because<span class="_"> </span>of<span class="_"> </span>the<span class="_"> </span>consideration<span class="_ _d"> </span>of</div><div class="t m0 x6 h6 y36 ff7 fs4 fc0 sc0 ls0 ws0">b<span class="_ _a"></span>oth<span class="_ _3"> </span>kinds<span class="_ _9"> </span>of<span class="_ _3"> </span>features,<span class="_ _3"> </span>our<span class="_ _3"> </span>proposal<span class="_ _3"> </span>also<span class="_ _3"> </span>pro<span class="_ _a"></span>duces<span class="_ _3"> </span>ric<span class="_ _f"></span>h</div><div class="t m0 x6 h6 y59 ff7 fs4 fc0 sc0 ls0 ws0">geometrical<span class="_ _9"> </span>maps.</div><div class="t m0 x7 h9 y5a ffc fs4 fc0 sc0 ls0 ws0">&#9702;<span class="_ _c"> </span><span class="ff7">A<span class="_ _7"> </span>new<span class="_ _10"> </span>implementation<span class="_ _10"> </span>of<span class="_ _10"> </span>the<span class="_ _7"> </span>bundle<span class="_ _10"> </span>adjustment<span class="_ _10"> </span>pro<span class="_ _a"></span>cess</span></div><div class="t m0 x6 h6 y3a ff7 fs4 fc0 sc0 ls0 ws0">that<span class="_ _7"> </span>seamlessly<span class="_ _10"> </span>accounts<span class="_ _10"> </span>for<span class="_ _7"> </span>b<span class="_ _a"></span>oth<span class="_ _7"> </span>kinds<span class="_ _7"> </span>of<span class="_ _7"> </span>features<span class="_ _10"> </span>while</div><div class="t m0 xd h6 y8f ff7 fs4 fc0 sc0 ls0 ws0">re&#64257;ning<span class="_ _9"> </span>the<span class="_ _9"> </span>poses<span class="_ _9"> </span>of<span class="_ _9"> </span>the<span class="_ _9"> </span>keyframes.</div><div class="t m0 xc h9 y5d ffc fs4 fc0 sc0 ls0 ws0">&#9702;<span class="_ _c"> </span><span class="ff7">An<span class="_"> </span>extension<span class="_"> </span>of<span class="_"> </span>the<span class="_ _d"> </span>bag-of-words<span class="_ _d"> </span>approach<span class="_ _d"> </span>presented</span></div><div class="t m0 xd h6 y5e ff7 fs4 fc0 sc0 ls0 ws0">in<span class="_ _3"> </span>[21]<span class="_ _6"> </span>that<span class="_ _6"> </span>tak<span class="_ _1"></span>es<span class="_ _6"> </span>in<span class="_ _1"></span>to<span class="_ _6"> </span>accoun<span class="_ _1"></span>t<span class="_ _6"> </span>the<span class="_ _3"> </span>description<span class="_ _6"> </span>of<span class="_ _3"> </span>b<span class="_ _2"></span>oth</div><div class="t m0 xd h6 y5f ff7 fs4 fc0 sc0 ls0 ws0">p<span class="_ _a"></span>oin<span class="_ _f"></span>ts<span class="_"> </span>and<span class="_"> </span>line<span class="_"> </span>segmen<span class="_ _1"></span>ts<span class="_"> </span>to<span class="_"> </span>improv<span class="_ _1"></span>e<span class="_"> </span>the<span class="_"> </span>lo<span class="_ _a"></span>op-closure</div><div class="t m0 xd h6 y60 ff7 fs4 fc0 sc0 ls0 ws0">pro<span class="_ _a"></span>cess.</div><div class="t m0 xc h6 y90 ff7 fs4 fc0 sc0 ls0 ws0">A<span class="_ _5"> </span>set<span class="_ _1a"> </span>of<span class="_ _1a"> </span>illustrativ<span class="_ _1"></span>e<span class="_ _1a"> </span>videos<span class="_ _1a"> </span>sho<span class="_ _1"></span>wing<span class="_ _1a"> </span>the<span class="_ _1a"> </span>performance</div><div class="t m0 xc h6 y91 ff7 fs4 fc0 sc0 ls0 ws0">of<span class="_ _13"> </span>prop<span class="_ _a"></span>osed<span class="_ _13"> </span>system<span class="_ _13"> </span>and<span class="_ _17"> </span>an<span class="_ _13"> </span>open<span class="_ _13"> </span>source<span class="_ _13"> </span>version</div><div class="t m0 xc h6 y92 ff7 fs4 fc0 sc0 ls0 ws0">of<span class="_ _1b"> </span>the<span class="_ _1b"> </span>dev<span class="_ _1"></span>elop<span class="_ _2"></span>ed<span class="_ _1b"> </span>C++<span class="_ _1b"> </span>PL-SLAM<span class="_ _1b"> </span>library<span class="_ _1b"> </span>are</div><div class="t m0 xc h6 y93 ff7 fs4 fc0 sc0 ls0 ws0">publicly<span class="_ _1c"> </span>a<span class="_ _1"></span>v<span class="_ _1"></span>ailable<span class="_ _1c"> </span>at<span class="_ _1c"> </span>http://mapir.uma.es<span class="_ _1c"> </span>and</div><div class="t m0 xc h6 y94 ff7 fs4 fc0 sc0 ls0 ws0">h<span class="_ _1"></span>ttps://github.com/rubengo<span class="_ _2"></span>o<span class="_ _a"></span>j/pl-slam.</div><div class="t m0 xf h6 y95 ff6 fs4 fc0 sc0 ls0 ws0">I<span class="_ _a"></span>I.<span class="_ _18"> </span>Rela<span class="_ _1"></span>ted<span class="_ _3"> </span>W<span class="_ _1"></span>ork</div><div class="t m0 xd h6 y96 ff7 fs4 fc0 sc0 ls0 ws0">F<span class="_ _4"></span>eature-based<span class="_ _1d"> </span>SLAM<span class="_ _1d"> </span>is<span class="_ _1d"> </span>traditionally<span class="_ _1d"> </span>addressed<span class="_ _1e"> </span>b<span class="_ _1"></span>y</div><div class="t m0 xc h6 y97 ff7 fs4 fc0 sc0 ls0 ws0">trac<span class="_ _1"></span>king<span class="_ _1e"> </span>keypoints<span class="_ _1f"> </span>along<span class="_ _1f"> </span>successive<span class="_ _1f"> </span>frames<span class="_ _1e"> </span>and<span class="_ _1f"> </span>then</div><div class="t m0 xc h6 y98 ff7 fs4 fc0 sc0 ls0 ws0">minimizing<span class="_"> </span>some<span class="_ _18"> </span>error<span class="_ _18"> </span>function<span class="_ _19"> </span>(typically<span class="_"> </span>based<span class="_ _18"> </span>on<span class="_ _18"> </span>re-</div><div class="t m0 xc h6 y99 ff7 fs4 fc0 sc0 ls0 ws0">pro<span class="_ _a"></span>jection<span class="_ _7"> </span>errors)<span class="_ _8"> </span>to<span class="_ _7"> </span>estimate<span class="_ _8"> </span>the<span class="_ _7"> </span>rob<span class="_ _2"></span>ot<span class="_ _7"> </span>p<span class="_ _a"></span>oses<span class="_ _8"> </span>[22].<span class="_ _7"> </span>Among</div><div class="t m0 xc h6 y9a ff7 fs4 fc0 sc0 ls0 ws0">the<span class="_ _8"> </span>most<span class="_ _8"> </span>successful<span class="_ _8"> </span>prop<span class="_ _a"></span>osals<span class="_ _8"> </span>we<span class="_ _8"> </span>can<span class="_ _8"> </span>highligh<span class="_ _1"></span>t<span class="_ _8"> </span>F<span class="_ _4"></span>astSLAM</div><div class="t m0 xc h6 y9b ff7 fs4 fc0 sc0 ls0 ws0">[23],<span class="_ _6"> </span>PT<span class="_ _4"></span>AM<span class="_ _6"> </span>[24]<span class="_ _6"> </span>[25],<span class="_ _6"> </span>SV<span class="_ _1"></span>O<span class="_ _6"> </span>[26]<span class="_ _6"> </span>[10],<span class="_ _6"> </span>and,<span class="_ _6"> </span>more<span class="_ _6"> </span>recently<span class="_ _4"></span>,</div><div class="t m0 xc h6 y9c ff7 fs4 fc0 sc0 ls0 ws0">ORB-SLAM<span class="_ _d"> </span>[13],<span class="_"> </span>whic<span class="_ _1"></span>h<span class="_"> </span>relies<span class="_ _d"> </span>on<span class="_ _d"> </span>a<span class="_"> </span>fast<span class="_ _d"> </span>and<span class="_"> </span>con<span class="_ _1"></span>tin<span class="_ _f"></span>uous</div><div class="t m0 xc h6 y9d ff7 fs4 fc0 sc0 ls0 ws0">trac<span class="_ _1"></span>king<span class="_ _3"> </span>of<span class="_ _9"> </span>ORB<span class="_ _9"> </span>features<span class="_ _9"> </span>[27],<span class="_ _9"> </span>and<span class="_ _3"> </span>a<span class="_ _9"> </span>lo<span class="_ _a"></span>cal<span class="_ _9"> </span>bundle<span class="_ _9"> </span>adjust-</div><div class="t m0 xc h6 y9e ff7 fs4 fc0 sc0 ls0 ws0">men<span class="_ _1"></span>t<span class="_ _6"> </span>step<span class="_ _6"> </span>with<span class="_ _6"> </span>the<span class="_ _6"> </span>con<span class="_ _1"></span>tinuous<span class="_ _3"> </span>observ<span class="_ _1"></span>ations<span class="_ _6"> </span>of<span class="_ _6"> </span>the<span class="_ _6"> </span>point</div><div class="t m0 xc h6 y9f ff7 fs4 fc0 sc0 ls0 ws0">features.<span class="_ _18"> </span>How<span class="_ _1"></span>ever,<span class="_ _18"> </span>all<span class="_ _18"> </span>of<span class="_ _e"> </span>the<span class="_ _e"> </span>previous<span class="_ _e"> </span>approac<span class="_ _f"></span>hes<span class="_ _18"> </span>tend</div><div class="t m0 xc h6 ya0 ff7 fs4 fc0 sc0 ls0 ws0">to<span class="_ _3"> </span>fail<span class="_ _3"> </span>or<span class="_ _3"> </span>reduce<span class="_ _3"> </span>their<span class="_ _3"> </span>accuracy<span class="_ _6"> </span>in<span class="_ _9"> </span>low-textured<span class="_ _3"> </span>scenarios</div><div class="t m0 xc h6 ya1 ff7 fs4 fc0 sc0 ls0 ws0">where<span class="_ _9"> </span>the<span class="_ _9"> </span>lack<span class="_ _9"> </span>of<span class="_ _9"> </span>rep<span class="_ _a"></span>eatable<span class="_ _9"> </span>and<span class="_ _3"> </span>reliable<span class="_ _9"> </span>features<span class="_ _9"> </span>usually</div><div class="t m0 xc h6 ya2 ff7 fs4 fc0 sc0 ls0 ws0">hinders<span class="_ _9"> </span>the<span class="_ _3"> </span>feature<span class="_ _3"> </span>tracking<span class="_ _9"> </span>process.<span class="_ _3"> </span>In<span class="_ _3"> </span>the<span class="_ _3"> </span>follo<span class="_ _1"></span>wing,<span class="_ _3"> </span>we</div><div class="t m0 xc h6 ya3 ff7 fs4 fc0 sc0 ls0 ws0">review<span class="_"> </span>the<span class="_"> </span>state<span class="_ _d"> </span>of<span class="_"> </span>the<span class="_"> </span>art<span class="_ _d"> </span>of<span class="_"> </span>SLAM<span class="_"> </span>systems<span class="_ _d"> </span>based<span class="_"> </span>on</div><div class="t m0 xc h6 ya4 ff7 fs4 fc0 sc0 ls0 ws0">alternativ<span class="_ _1"></span>e<span class="_ _8"> </span>image<span class="_ _7"> </span>features<span class="_ _8"> </span>to<span class="_ _7"> </span>keypoints:<span class="_ _7"> </span>i.e.<span class="_ _8"> </span>edgelets,<span class="_ _7"> </span>lines,</div><div class="t m0 xc h6 ya5 ff7 fs4 fc0 sc0 ls0 ws0">or<span class="_ _9"> </span>line<span class="_ _9"> </span>segmen<span class="_ _1"></span>ts.</div><div class="t m0 xd h6 ya6 ff7 fs4 fc0 sc0 ls0 ws0">One<span class="_"> </span>of<span class="_ _18"> </span>the<span class="_"> </span>remarkable<span class="_ _18"> </span>approac<span class="_ _f"></span>hes<span class="_"> </span>that<span class="_ _18"> </span>emplo<span class="_ _f"></span>ys<span class="_"> </span><span class="ff8">line</span></div><div class="t m0 xc h6 ya7 ff7 fs4 fc0 sc0 ls0 ws0">features<span class="_ _3"> </span>is<span class="_ _3"> </span>the<span class="_ _3"> </span>one<span class="_ _3"> </span>in<span class="_ _3"> </span>[28],<span class="_ _3"> </span>where<span class="_ _6"> </span>the<span class="_ _9"> </span>authors<span class="_ _3"> </span>prop<span class="_ _a"></span>ose<span class="_ _6"> </span>an</div><div class="t m0 xc h6 ya8 ff7 fs4 fc0 sc0 ls0 ws0">algorithm<span class="_ _6"> </span>to<span class="_ _6"> </span>integrate<span class="_ _6"> </span>them<span class="_ _6"> </span>into<span class="_ _6"> </span>a<span class="_ _6"> </span>monocular<span class="_ _d"> </span>Extended</div><div class="t m0 xc h6 ya9 ff7 fs4 fc0 sc0 ls0 ws0">Kalman<span class="_ _7"> </span>Filter<span class="_ _7"> </span>SLAM<span class="_ _7"> </span>system<span class="_ _7"> </span>(EKF-SLAM).<span class="_ _7"> </span>In<span class="_ _7"> </span>the<span class="_ _7"> </span>refered</div><div class="t m0 xc h6 yaa ff7 fs4 fc0 sc0 ls0 ws0">pap<span class="_ _a"></span>er,<span class="_ _8"> </span>the<span class="_ _8"> </span>line<span class="_ _8"> </span>detection<span class="_ _8"> </span>relies<span class="_ _8"> </span>on<span class="_ _8"> </span>an<span class="_ _8"> </span>h<span class="_ _f"></span>yp<span class="_ _a"></span>othesize-and-test</div><div class="t m0 xc h6 yab ff7 fs4 fc0 sc0 ls0 ws0">metho<span class="_ _a"></span>d<span class="_"> </span>that<span class="_ _6"> </span>connects<span class="_"> </span>sev<span class="_ _1"></span>eral<span class="_"> </span>near<span class="_ _d"> </span>keypoints<span class="_ _6"> </span>to<span class="_"> </span>ac<span class="_ _1"></span>hieve</div><div class="t m0 xc h6 yac ff7 fs4 fc0 sc0 ls0 ws0">real-time<span class="_ _e"> </span>p<span class="_ _a"></span>erformance.<span class="_ _e"> </span>Other<span class="_ _e"> </span>works<span class="_ _18"> </span>emplo<span class="_ _f"></span>y<span class="_ _e"> </span><span class="ff8">e<span class="_ _1"></span>dge<span class="_ _b"> </span><span class="ff7">land-</span></span></div><div class="t m0 xc h6 yad ff7 fs4 fc0 sc0 ls0 ws0">marks<span class="_ _10"> </span>as<span class="_ _10"> </span>features<span class="_ _7"> </span>in<span class="_ _10"> </span>mono<span class="_ _a"></span>cular<span class="_ _7"> </span>SLAM,<span class="_ _10"> </span>as<span class="_ _10"> </span>the<span class="_ _7"> </span>one<span class="_ _10"> </span>rep<span class="_ _a"></span>orted</div><div class="t m0 xc h6 yae ff7 fs4 fc0 sc0 ls0 ws0">in<span class="_"> </span>[29],<span class="_"> </span>wh<span class="_ _f"></span>ic<span class="_ _f"></span>h<span class="_"> </span>does<span class="_"> </span>not<span class="_"> </span>only<span class="_"> </span>in<span class="_ _f"></span>clude<span class="_"> </span>the<span class="_"> </span>information<span class="_ _d"> </span>of</div><div class="t m0 xc h6 yaf ff7 fs4 fc0 sc0 ls0 ws0">the<span class="_"> </span>local<span class="_"> </span>planar<span class="_"> </span>patch<span class="_"> </span>as<span class="_"> </span>in<span class="_ _d"> </span>the<span class="_"> </span>case<span class="_"> </span>of<span class="_"> </span>keypoints,<span class="_ _d"> </span>but</div><div class="t m0 xc h6 yb0 ff7 fs4 fc0 sc0 ls0 ws0">also<span class="_ _8"> </span>considers<span class="_ _8"> </span>lo<span class="_ _a"></span>cal<span class="_ _8"> </span>edge<span class="_ _9"> </span>segmen<span class="_ _1"></span>ts,<span class="_ _8"> </span>hence<span class="_ _8"> </span>introducing<span class="_ _9"> </span>new</div><div class="t m0 xc h6 yb1 ff7 fs4 fc0 sc0 ls0 ws0">v<span class="_ _1"></span>aluable<span class="_"> </span>information<span class="_"> </span>as<span class="_ _19"> </span>the<span class="_ _19"> </span>orientation<span class="_"> </span>of<span class="_"> </span>the<span class="_"> </span>so-called</div><div class="t m0 xc h6 yb2 ff8 fs4 fc0 sc0 ls0 ws0">e<span class="_ _1"></span>dgelets<span class="ff7">.<span class="_ _7"> </span>In<span class="_ _10"> </span>that<span class="_ _7"> </span>work<span class="_ _10"> </span>they<span class="_ _7"> </span>deriv<span class="_ _f"></span>e<span class="_ _10"> </span>suitable<span class="_ _7"> </span>mo<span class="_ _a"></span>dels<span class="_ _7"> </span>for<span class="_ _7"> </span>those</span></div><div class="t m0 xc h6 yb3 ff7 fs4 fc0 sc0 ls0 ws0">kinds<span class="_ _e"> </span>of<span class="_ _e"> </span>features<span class="_ _e"> </span>and<span class="_ _e"> </span>use<span class="_ _e"> </span>them<span class="_ _e"> </span>within<span class="_ _e"> </span>a<span class="_ _e"> </span>particle-&#64257;lter</div><div class="t m0 xc h6 yb4 ff7 fs4 fc0 sc0 ls0 ws0">SLAM<span class="_ _18"> </span>system,<span class="_ _e"> </span>achieving<span class="_ _18"> </span>nearly<span class="_ _e"> </span>real-time<span class="_ _e"> </span>p<span class="_ _a"></span>erformance.</div><div class="t m0 xc h6 yb5 ff7 fs4 fc0 sc0 ls0 ws0">More<span class="_ _9"> </span>recently<span class="_ _4"></span>,<span class="_ _9"> </span>authors<span class="_ _3"> </span>in<span class="_ _3"> </span>[10]<span class="_ _3"> </span>also<span class="_ _9"> </span>introduced<span class="_ _3"> </span>edgelets<span class="_ _3"> </span>in</div><div class="t m0 xc h6 yb6 ff7 fs4 fc0 sc0 ls0 ws0">com<span class="_ _1"></span>bination<span class="_ _19"> </span>with<span class="_ _19"> </span>intensit<span class="_ _1"></span>y<span class="_"> </span>corners<span class="_"> </span>in<span class="_ _19"> </span>order<span class="_ _19"> </span>to<span class="_"> </span>improv<span class="_ _1"></span>e</div><div class="t m0 xc h6 yb7 ff7 fs4 fc0 sc0 ls0 ws0">robustness<span class="_ _6"> </span>in<span class="_ _d"> </span>en<span class="_ _f"></span>vironmen<span class="_ _1"></span>ts<span class="_ _d"> </span>with<span class="_ _d"> </span>little<span class="_ _6"> </span>or<span class="_ _d"> </span>high-frequency</div><div class="t m0 xc h6 yb8 ff7 fs4 fc0 sc0 ls0 ws0">texture.</div><div class="t m0 xd h6 y8b ff7 fs4 fc0 sc0 ls0 ws0">A<span class="_ _0"> </span>di&#64256;erent<span class="_ _0"> </span>approach,<span class="_ _0"> </span>known<span class="_ _0"> </span>as<span class="_ _5"> </span><span class="ff8">mo<span class="_ _1"></span>del-b<span class="_ _1"></span>ase<span class="_ _1"></span>d<span class="ff7">,<span class="_ _5"> </span>incor-</span></span></div><div class="t m0 xc h6 y8c ff7 fs4 fc0 sc0 ls0 ws0">p<span class="_ _a"></span>orates<span class="_ _e"> </span>prior<span class="_ _e"> </span>information<span class="_ _e"> </span>ab<span class="_ _a"></span>out<span class="_ _e"> </span>the<span class="_ _e"> </span>orientation<span class="_ _18"> </span>of<span class="_ _e"> </span>the</div><div class="t m0 xc h6 y8d ff7 fs4 fc0 sc0 ls0 ws0">landmarks<span class="_"> </span>deriv<span class="_ _1"></span>ed<span class="_"> </span>from<span class="_"> </span>line<span class="_"> </span>segmen<span class="_ _1"></span>ts.<span class="_"> </span>P<span class="_ _1"></span>articularly<span class="_ _1"></span>,<span class="_"> </span>the</div><div class="t m0 xc h6 y32 ff7 fs4 fc0 sc0 ls0 ws0">metho<span class="_ _a"></span>d<span class="_"> </span>in<span class="_ _6"> </span>[30]<span class="_"> </span>presen<span class="_ _1"></span>ts<span class="_"> </span>a<span class="_ _d"> </span>mono<span class="_ _a"></span>cular<span class="_"> </span>2D<span class="_ _6"> </span>SLAM<span class="_"> </span>system</div><div class="t m0 xc h6 yb9 ff7 fs4 fc0 sc0 ls0 ws0">that<span class="_ _9"> </span>employs<span class="_ _9"> </span>vertical<span class="_ _9"> </span>and<span class="_ _3"> </span>horizontal<span class="_ _9"> </span>lines<span class="_ _3"> </span>on<span class="_ _9"> </span>the<span class="_ _3"> </span>&#64258;o<span class="_ _a"></span>or<span class="_ _3"> </span>as</div><div class="t m0 xc h6 y8e ff7 fs4 fc0 sc0 ls0 ws0">features<span class="_ _6"> </span>for<span class="_ _d"> </span>b<span class="_ _a"></span>oth<span class="_ _d"> </span>motion<span class="_ _6"> </span>and<span class="_ _d"> </span>map<span class="_ _d"> </span>estimation.<span class="_ _6"> </span>F<span class="_ _1"></span>or<span class="_ _6"> </span>that,</div><div class="t m0 xc h6 y36 ff7 fs4 fc0 sc0 ls0 ws0">they<span class="_ _7"> </span>prop<span class="_ _2"></span>ose<span class="_ _8"> </span>t<span class="_ _1"></span>wo<span class="_ _7"> </span>di&#64256;eren<span class="_ _f"></span>t<span class="_ _8"> </span>parameterizations<span class="_ _7"> </span>for<span class="_ _8"> </span>the<span class="_ _7"> </span>verti-</div><div class="t m0 xc h6 y59 ff7 fs4 fc0 sc0 ls0 ws0">cal<span class="_ _9"> </span>and<span class="_ _9"> </span>the<span class="_ _9"> </span>horizontal<span class="_ _9"> </span>lines:<span class="_ _9"> </span>vertical<span class="_ _9"> </span>lines<span class="_ _9"> </span>are<span class="_ _9"> </span>represented</div><div class="t m0 xc h6 y5a ff7 fs4 fc0 sc0 ls0 ws0">as<span class="_ _6"> </span>2D<span class="_ _d"> </span>p<span class="_ _a"></span>oints<span class="_ _6"> </span>on<span class="_ _6"> </span>the<span class="_ _d"> </span>&#64258;o<span class="_ _a"></span>or<span class="_ _d"> </span>plane<span class="_ _6"> </span>(placed<span class="_ _d"> </span>the<span class="_ _6"> </span>intersection</div><div class="t m0 xc h6 yba ff7 fs4 fc0 sc0 ls0 ws0">p<span class="_ _a"></span>oin<span class="_ _f"></span>t<span class="_ _3"> </span>b<span class="_ _2"></span>et<span class="_ _1"></span>ween<span class="_ _3"> </span>the<span class="_ _6"> </span>line<span class="_ _3"> </span>and<span class="_ _6"> </span>suc<span class="_ _f"></span>h<span class="_ _6"> </span>plane),<span class="_ _3"> </span>while<span class="_ _6"> </span>horizon<span class="_ _1"></span>tal</div><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a></div><div class="pi" data-data='{"ctm":[1.568627,0.000000,0.000000,1.568627,0.000000,0.000000]}'></div></div><div id="pf3" class="pf w0 h0" data-page-no="3"><div class="pc pc3 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="/image.php?url=https://csdnimg.cn/release/download_crawler_static/89541504/bg3.jpg"><div class="t m0 x1 h2 y1 ff1 fs0 fc0 sc0 ls0 ws0">3</div><div class="t m0 x7 h6 y5c ff7 fs4 fc0 sc0 ls0 ws0">lines<span class="_"> </span>are<span class="_ _d"> </span>represented<span class="_ _d"> </span>by<span class="_ _d"> </span>their<span class="_"> </span>t<span class="_ _1"></span>wo<span class="_ _d"> </span>end-p<span class="_ _a"></span>oints<span class="_ _d"> </span>placed<span class="_"> </span>on</div><div class="t m0 x7 h6 y5d ff7 fs4 fc0 sc0 ls0 ws0">the<span class="_ _10"> </span>&#64258;o<span class="_ _a"></span>or.<span class="_ _7"> </span>Finally<span class="_ _4"></span>,<span class="_ _7"> </span>the<span class="_ _7"> </span>prop<span class="_ _a"></span>osed<span class="_ _7"> </span>models<span class="_ _7"> </span>is<span class="_ _7"> </span>incorp<span class="_ _a"></span>orated<span class="_ _7"> </span>in<span class="_ _1"></span>to</div><div class="t m0 x7 h6 y5e ff7 fs4 fc0 sc0 ls0 ws0">an<span class="_ _8"> </span>EKF-SLAM<span class="_ _8"> </span>system.<span class="_ _9"> </span>Another<span class="_ _8"> </span>mo<span class="_ _a"></span>del-based<span class="_ _8"> </span>approach<span class="_ _8"> </span>is</div><div class="t m0 x7 h6 y5f ff7 fs4 fc0 sc0 ls0 ws0">rep<span class="_ _a"></span>orted<span class="_ _d"> </span>in<span class="_ _d"> </span>[31],<span class="_ _d"> </span>where<span class="_ _d"> </span>the<span class="_ _d"> </span>authors<span class="_ _d"> </span>introduce<span class="_ _d"> </span>structural</div><div class="t m0 x7 h6 y60 ff7 fs4 fc0 sc0 ls0 ws0">lines<span class="_ _6"> </span>in<span class="_ _d"> </span>an<span class="_ _6"> </span>extension<span class="_ _d"> </span>of<span class="_ _d"> </span>a<span class="_ _6"> </span>standard<span class="_ _d"> </span>EKF-SLAM<span class="_ _6"> </span>system.</div><div class="t m0 x7 h6 y61 ff7 fs4 fc0 sc0 ls0 ws0">The<span class="_ _10"> </span>dominant<span class="_ _10"> </span>directions<span class="_ _10"> </span>of<span class="_ _7"> </span>the<span class="_ _10"> </span>lines<span class="_ _7"> </span>are<span class="_ _10"> </span>estimated<span class="_ _10"> </span>by<span class="_ _10"> </span>com-</div><div class="t m0 x7 h6 y62 ff7 fs4 fc0 sc0 ls0 ws0">puting<span class="_ _6"> </span>their<span class="_ _6"> </span>v<span class="_ _4"></span>anishing<span class="_ _6"> </span>p<span class="_ _a"></span>oints<span class="_ _6"> </span>under<span class="_ _3"> </span>the<span class="_ _6"> </span>assumption<span class="_ _6"> </span>of<span class="_ _6"> </span>a</div><div class="t m0 x7 h6 y63 ff7 fs4 fc0 sc0 ls0 ws0">Manhattan<span class="_ _9"> </span>w<span class="_ _1"></span>orld<span class="_ _9"> </span>[32].<span class="_ _9"> </span>All<span class="_ _8"> </span>these<span class="_ _9"> </span>mo<span class="_ _a"></span>del-based<span class="_ _9"> </span>approac<span class="_ _1"></span>hes,</div><div class="t m0 x7 h6 y64 ff7 fs4 fc0 sc0 ls0 ws0">though,<span class="_ _d"> </span>are<span class="_"> </span>limited<span class="_ _d"> </span>to<span class="_"> </span>v<span class="_ _1"></span>ery<span class="_ _d"> </span>structured<span class="_"> </span>scenarios<span class="_ _d"> </span>and/or</div><div class="t m0 x7 h6 y65 ff7 fs4 fc0 sc0 ls0 ws0">planar<span class="_ _9"> </span>motions,<span class="_ _9"> </span>as<span class="_ _9"> </span>they<span class="_ _9"> </span>rely<span class="_ _8"> </span>solely<span class="_ _9"> </span>on<span class="_ _9"> </span>line<span class="_ _9"> </span>features.</div><div class="t m0 x6 h6 y6 ff7 fs4 fc0 sc0 ls0 ws0">The<span class="_ _b"> </span>works<span class="_ _b"> </span>in<span class="_ _0"> </span>[16],<span class="_ _b"> </span>[33]<span class="_ _0"> </span>address<span class="_ _b"> </span>a<span class="_ _0"> </span>generic<span class="_ _0"> </span>approac<span class="_ _1"></span>h</div><div class="t m0 x7 h6 y66 ff7 fs4 fc0 sc0 ls0 ws0">that<span class="_ _b"> </span>compares<span class="_ _b"> </span>the<span class="_ _b"> </span>impact<span class="_ _b"> </span>of<span class="_ _b"> </span>eigh<span class="_ _f"></span>t<span class="_ _b"> </span>di&#64256;eren<span class="_ _1"></span>t<span class="_ _b"> </span>landmark</div><div class="t m0 x7 h6 y67 ff7 fs4 fc0 sc0 ls0 ws0">parametrization<span class="_ _8"> </span>for<span class="_ _8"> </span>monocular<span class="_ _8"> </span>EKF-SLAM,<span class="_ _8"> </span>including<span class="_ _8"> </span>the</div><div class="t m0 x7 h6 ybb ff7 fs4 fc0 sc0 ls0 ws0">use<span class="_ _9"> </span>of<span class="_ _9"> </span>p<span class="_ _a"></span>oint<span class="_ _8"> </span>and<span class="_ _9"> </span>line<span class="_ _3"> </span>features.<span class="_ _9"> </span>Nev<span class="_ _1"></span>ertheless,<span class="_ _9"> </span>such<span class="_ _9"> </span>systems</div><div class="t m0 x7 h6 ybc ff7 fs4 fc0 sc0 ls0 ws0">are<span class="_ _6"> </span>only<span class="_"> </span>v<span class="_ _4"></span>alidated<span class="_ _d"> </span>through<span class="_ _d"> </span>analytic<span class="_ _d"> </span>and<span class="_ _d"> </span>statistical<span class="_ _d"> </span>to<span class="_ _a"></span>ols</div><div class="t m0 x7 h6 yc ff7 fs4 fc0 sc0 ls0 ws0">that<span class="_ _d"> </span>assumed<span class="_ _d"> </span>already<span class="_ _d"> </span>known<span class="_ _6"> </span>data<span class="_"> </span>association<span class="_ _d"> </span>and<span class="_ _d"> </span>that,</div><div class="t m0 x7 h6 ybd ff7 fs4 fc0 sc0 ls0 ws0">unlik<span class="_ _1"></span>e<span class="_ _6"> </span>our<span class="_ _3"> </span>prop<span class="_ _a"></span>osal,<span class="_ _6"> </span>do<span class="_ _3"> </span>not<span class="_ _6"> </span>implemen<span class="_ _1"></span>t<span class="_ _6"> </span>a<span class="_ _3"> </span>complete<span class="_ _6"> </span>fron<span class="_ _1"></span>t-</div><div class="t m0 x7 h6 ybe ff7 fs4 fc0 sc0 ls0 ws0">end<span class="_ _e"> </span>that<span class="_ _e"> </span>detect<span class="_ _b"> </span>and<span class="_ _e"> </span>track<span class="_ _18"> </span>the<span class="_ _b"> </span>line<span class="_ _18"> </span>segments.<span class="_ _e"> </span>Another</div><div class="t m0 x7 h6 ybf ff7 fs4 fc0 sc0 ls0 ws0">tec<span class="_ _1"></span>hnique<span class="_ _3"> </span>for<span class="_ _9"> </span>building<span class="_ _9"> </span>a<span class="_ _3"> </span>3D<span class="_ _9"> </span>line-based<span class="_ _9"> </span>SLAM<span class="_ _9"> </span>system<span class="_ _3"> </span>has</div><div class="t m0 x7 h6 yc0 ff7 fs4 fc0 sc0 ls0 ws0">b<span class="_ _a"></span>een<span class="_ _b"> </span>prop<span class="_ _a"></span>osed<span class="_ _b"> </span>in<span class="_ _b"> </span>the<span class="_ _0"> </span>recen<span class="_ _1"></span>t<span class="_ _0"> </span>w<span class="_ _1"></span>ork<span class="_ _b"> </span>[34].<span class="_ _0"> </span>F<span class="_ _4"></span>or<span class="_ _b"> </span>that,<span class="_ _b"> </span>the</div><div class="t m0 x7 h6 y12 ff7 fs4 fc0 sc0 ls0 ws0">authors<span class="_ _6"> </span>emplo<span class="_ _1"></span>y<span class="_ _6"> </span>t<span class="_ _1"></span>wo<span class="_ _3"> </span>di&#64256;erent<span class="_ _3"> </span>representations<span class="_ _3"> </span>for<span class="_ _6"> </span>the<span class="_ _6"> </span>line</div><div class="t m0 x7 h6 yc1 ff7 fs4 fc0 sc0 ls0 ws0">segmen<span class="_ _1"></span>ts:<span class="_ _7"> </span>the<span class="_ _10"> </span>Pl&#252;ck<span class="_ _1"></span>er<span class="_ _10"> </span>line<span class="_ _7"> </span>co<span class="_ _a"></span>ordinates<span class="_ _10"> </span>for<span class="_ _7"> </span>the<span class="_ _10"> </span>initialization</div><div class="t m0 x7 h6 yc2 ff7 fs4 fc0 sc0 ls0 ws0">and<span class="_"> </span>3D<span class="_"> </span>pro<span class="_ _a"></span>jections,<span class="_"> </span>and<span class="_"> </span>an<span class="_"> </span>orthonormal<span class="_"> </span>represen<span class="_ _1"></span>tation</div><div class="t m0 x7 h6 yc3 ff7 fs4 fc0 sc0 ls0 ws0">for<span class="_ _9"> </span>the<span class="_ _9"> </span>back-end<span class="_ _9"> </span>optimization.<span class="_ _9"> </span>Unfortunately<span class="_ _4"></span>,<span class="_ _9"> </span>neither<span class="_ _9"> </span>the</div><div class="t m0 x7 h6 yc4 ff7 fs4 fc0 sc0 ls0 ws0">source<span class="_ _9"> </span>code<span class="_ _9"> </span>is<span class="_ _9"> </span>a<span class="_ _f"></span>v<span class="_ _1"></span>ailable<span class="_ _9"> </span>nor<span class="_ _8"> </span>the<span class="_ _9"> </span>employ<span class="_ _1"></span>ed<span class="_ _9"> </span>dataset<span class="_ _9"> </span>con<span class="_ _1"></span>tain</div><div class="t m0 x7 h6 y18 ff7 fs4 fc0 sc0 ls0 ws0">an<span class="_ _1"></span>y<span class="_"> </span>ground-truth,<span class="_"> </span>therefore<span class="_"> </span>it<span class="_"> </span>has<span class="_"> </span>not<span class="_ _d"> </span>b<span class="_ _a"></span>een<span class="_"> </span>p<span class="_ _a"></span>ossible<span class="_"> </span>to</div><div class="t m0 x7 h6 yc5 ff7 fs4 fc0 sc0 ls0 ws0">carry<span class="_ _9"> </span>out<span class="_ _9"> </span>a<span class="_ _9"> </span>comparison<span class="_ _9"> </span>against<span class="_ _8"> </span>our<span class="_ _9"> </span>prop<span class="_ _a"></span>osal.</div><div class="t m0 x6 h6 yc6 ff7 fs4 fc0 sc0 ls0 ws0">Recen<span class="_ _1"></span>tly<span class="_ _1"></span>,<span class="_ _7"> </span>line<span class="_ _7"> </span>segment<span class="_ _7"> </span>features<span class="_ _7"> </span>hav<span class="_ _1"></span>e<span class="_ _8"> </span>also<span class="_ _10"> </span>b<span class="_ _2"></span>een<span class="_ _7"> </span>employ<span class="_ _1"></span>ed</div><div class="t m0 x7 h6 yc7 ff7 fs4 fc0 sc0 ls0 ws0">for<span class="_ _7"> </span>mono<span class="_ _a"></span>cular<span class="_ _7"> </span>p<span class="_ _a"></span>ose<span class="_ _7"> </span>estimation<span class="_ _7"> </span>in<span class="_ _7"> </span>com<span class="_ _1"></span>bination<span class="_ _7"> </span>with<span class="_ _7"> </span>p<span class="_ _a"></span>oints,</div><div class="t m0 x7 h6 yc8 ff7 fs4 fc0 sc0 ls0 ws0">due<span class="_"> </span>to<span class="_ _6"> </span>the<span class="_"> </span>bad-conditioned<span class="_ _d"> </span>nature<span class="_"> </span>of<span class="_ _d"> </span>this<span class="_"> </span>problem.<span class="_ _d"> </span>F<span class="_ _4"></span>or</div><div class="t m0 x7 h6 y1e ff7 fs4 fc0 sc0 ls0 ws0">that,<span class="_ _10"> </span>in<span class="_ _10"> </span>[35]<span class="_ _7"> </span>the<span class="_ _10"> </span>authors<span class="_ _10"> </span>extended<span class="_ _7"> </span>the<span class="_ _10"> </span>semi-direct<span class="_ _10"> </span>approach</div><div class="t m0 x7 h6 yc9 ff7 fs4 fc0 sc0 ls0 ws0">in<span class="_ _6"> </span>[26]<span class="_"> </span>with<span class="_ _6"> </span>line<span class="_ _d"> </span>segmen<span class="_ _f"></span>ts.<span class="_ _6"> </span>Thanks<span class="_"> </span>to<span class="_ _6"> </span>this<span class="_ _d"> </span>pip<span class="_ _a"></span>eline,<span class="_ _d"> </span>line</div><div class="t m0 x7 h6 yca ff7 fs4 fc0 sc0 ls0 ws0">segmen<span class="_ _1"></span>ts<span class="_ _b"> </span>can<span class="_ _18"> </span>b<span class="_ _2"></span>e<span class="_ _e"> </span>propagated<span class="_ _e"> </span>e&#64259;ciently<span class="_ _18"> </span>throughout<span class="_ _b"> </span>the</div><div class="t m0 x7 h6 ycb ff7 fs4 fc0 sc0 ls0 ws0">image<span class="_"> </span>sequence,<span class="_"> </span>while<span class="_"> </span>re&#64257;ning<span class="_"> </span>the<span class="_ _19"> </span>p<span class="_ _a"></span>osition<span class="_ _19"> </span>of<span class="_"> </span>the<span class="_ _19"> </span>end-</div><div class="t m0 x7 h6 ycc ff7 fs4 fc0 sc0 ls0 ws0">p<span class="_ _a"></span>oin<span class="_ _f"></span>ts<span class="_ _8"> </span>under<span class="_ _9"> </span>the<span class="_ _8"> </span>assumptions<span class="_ _8"> </span>of<span class="_ _8"> </span>high<span class="_ _9"> </span>frame<span class="_ _8"> </span>rate<span class="_ _8"> </span>and<span class="_ _9"> </span>v<span class="_ _1"></span>ery</div><div class="t m0 x7 h6 ycd ff7 fs4 fc0 sc0 ls0 ws0">narro<span class="_ _1"></span>w-baseline.</div><div class="t m0 x6 h6 yce ff7 fs4 fc0 sc0 ls0 ws0">Finally<span class="_ _4"></span>,<span class="_ _b"> </span>by<span class="_ _b"> </span>the<span class="_ _b"> </span>time<span class="_ _b"> </span>of<span class="_ _b"> </span>the<span class="_ _b"> </span>&#64257;rst<span class="_ _b"> </span>submission<span class="_ _b"> </span>of<span class="_ _b"> </span>this</div><div class="t m0 x7 h6 ycf ff7 fs4 fc0 sc0 ls0 ws0">pap<span class="_ _a"></span>er,<span class="_ _9"> </span>a<span class="_ _3"> </span>w<span class="_ _1"></span>ork<span class="_ _3"> </span>with<span class="_ _9"> </span>the<span class="_ _3"> </span>same<span class="_ _9"> </span>name<span class="_ _3"> </span>(PL-SLAM,<span class="_ _9"> </span>[36])<span class="_ _3"> </span>w<span class="_ _1"></span>as</div><div class="t m0 x7 h6 yd0 ff7 fs4 fc0 sc0 ls0 ws0">published<span class="_ _10"> </span>extending<span class="_ _10"> </span>the<span class="_ _10"> </span>mono<span class="_ _a"></span>cular<span class="_ _10"> </span>algorithm<span class="_ _10"> </span>ORB-SLAM</div><div class="t m0 x7 h6 yd1 ff7 fs4 fc0 sc0 ls0 ws0">to<span class="_ _6"> </span>the<span class="_ _6"> </span>case<span class="_ _d"> </span>of<span class="_ _6"> </span>including<span class="_ _d"> </span>line<span class="_ _6"> </span>segment<span class="_ _6"> </span>features<span class="_ _6"> </span>computed</div><div class="t m0 x7 h6 yd2 ff7 fs4 fc0 sc0 ls0 ws0">through<span class="_ _7"> </span>the<span class="_ _10"> </span>LSD<span class="_ _7"> </span>detector<span class="_ _7"> </span>[37].<span class="_ _7"> </span>Apart<span class="_ _7"> </span>from<span class="_ _7"> </span>b<span class="_ _a"></span>eing<span class="_ _7"> </span>a<span class="_ _7"> </span>mono<span class="_ _a"></span>c-</div><div class="t m0 x7 h6 yd3 ff7 fs4 fc0 sc0 ls0 ws0">ular<span class="_ _6"> </span>system<span class="_ _6"> </span>(unlike<span class="_ _6"> </span>our<span class="_ _6"> </span>stereo<span class="_ _6"> </span>approach),<span class="_ _6"> </span>their<span class="_ _6"> </span>prop<span class="_ _a"></span>osal</div><div class="t m0 x7 h6 yd4 ff7 fs4 fc0 sc0 ls0 ws0">deals<span class="_"> </span>with<span class="_"> </span>line<span class="_"> </span>trac<span class="_ _1"></span>king<span class="_"> </span>and<span class="_"> </span>matching<span class="_"> </span>in<span class="_"> </span>an<span class="_"> </span>essen<span class="_ _1"></span>tially</div><div class="t m0 x7 h6 yd5 ff7 fs4 fc0 sc0 ls0 ws0">di&#64256;eren<span class="_ _1"></span>t<span class="_ _6"> </span>wa<span class="_ _1"></span>y:<span class="_ _6"> </span>they<span class="_ _6"> </span>propagate<span class="_ _6"> </span>the<span class="_ _3"> </span>line<span class="_ _6"> </span>segments<span class="_ _6"> </span>b<span class="_ _1"></span>y<span class="_ _6"> </span>their</div><div class="t m0 x7 h6 yd6 ff7 fs4 fc0 sc0 ls0 ws0">endp<span class="_ _a"></span>oin<span class="_ _f"></span>ts<span class="_ _b"> </span>and<span class="_ _b"> </span>then<span class="_ _b"> </span>perform<span class="_ _b"> </span>descriptor-based<span class="_ _b"> </span>tracking,</div><div class="t m0 x7 h6 yd7 ff7 fs4 fc0 sc0 ls0 ws0">whic<span class="_ _1"></span>h<span class="_ _8"> </span>increases<span class="_ _10"> </span>the<span class="_ _7"> </span>computational<span class="_ _7"> </span>burden<span class="_ _8"> </span>of<span class="_ _10"> </span>ORB-SLAM.</div><div class="t m0 x7 h6 yd8 ff7 fs4 fc0 sc0 ls0 ws0">Besides<span class="_ _8"> </span>this<span class="_ _9"> </span>computational<span class="_ _8"> </span>drawbac<span class="_ _1"></span>k,<span class="_ _9"> </span>when<span class="_ _8"> </span>working<span class="_ _8"> </span>with</div><div class="t m0 x7 h6 yd9 ff7 fs4 fc0 sc0 ls0 ws0">features<span class="_ _e"> </span>detected<span class="_ _b"> </span>with<span class="_ _e"> </span>the<span class="_ _e"> </span>LSD<span class="_ _b"> </span>detector,<span class="_ _e"> </span>the<span class="_ _e"> </span>v<span class="_ _1"></span>ariance</div><div class="t m0 x7 h6 y8b ff7 fs4 fc0 sc0 ls0 ws0">of<span class="_ _6"> </span>the<span class="_ _6"> </span>endp<span class="_ _a"></span>oints<span class="_ _6"> </span>becomes<span class="_ _6"> </span>quite<span class="_ _6"> </span>pronounced,<span class="_ _d"> </span>sp<span class="_ _a"></span>ecially<span class="_ _6"> </span>in</div><div class="t m0 x7 h6 y8c ff7 fs4 fc0 sc0 ls0 ws0">c<span class="_ _1"></span>hallenging<span class="_"> </span>illumination<span class="_ _d"> </span>conditions<span class="_"> </span>or<span class="_ _6"> </span>very<span class="_ _d"> </span>low-textured</div><div class="t m0 x7 h6 y8d ff7 fs4 fc0 sc0 ls0 ws0">scenes,<span class="_ _6"> </span>making<span class="_ _6"> </span>more<span class="_ _6"> </span>di&#64259;cult<span class="_ _6"> </span>wide-baseline<span class="_ _6"> </span>tracking<span class="_ _6"> </span>and</div><div class="t m0 x7 h6 y32 ff7 fs4 fc0 sc0 ls0 ws0">matc<span class="_ _1"></span>hing<span class="_ _8"> </span>b<span class="_ _a"></span>etw<span class="_ _1"></span>een<span class="_ _8"> </span>line<span class="_ _8"> </span>features<span class="_ _7"> </span>in<span class="_ _8"> </span>non-consecutive<span class="_ _7"> </span>frames.</div><div class="t m0 x7 h6 y56 ff7 fs4 fc0 sc0 ls0 ws0">Our<span class="_ _9"> </span>PL-SLAM<span class="_ _9"> </span>approach,<span class="_ _9"> </span>in<span class="_ _9"> </span>con<span class="_ _f"></span>trast,<span class="_ _9"> </span>do<span class="_ _a"></span>es<span class="_ _9"> </span>not<span class="_ _9"> </span>make<span class="_ _9"> </span>any</div><div class="t m0 x7 h6 y8e ff7 fs4 fc0 sc0 ls0 ws0">assumption<span class="_ _6"> </span>regarding<span class="_ _3"> </span>the<span class="_ _6"> </span>position<span class="_ _6"> </span>of<span class="_ _6"> </span>the<span class="_ _3"> </span>lines<span class="_ _6"> </span>endpoints</div><div class="t m0 x7 h6 y36 ff7 fs4 fc0 sc0 ls0 ws0">so<span class="_ _6"> </span>that<span class="_ _3"> </span>our<span class="_ _6"> </span>tracking<span class="_ _3"> </span>front-end<span class="_ _3"> </span>allows<span class="_ _3"> </span>to<span class="_ _6"> </span>handle<span class="_ _6"> </span>partially</div><div class="t m0 x7 h6 y59 ff7 fs4 fc0 sc0 ls0 ws0">o<span class="_ _a"></span>ccluded<span class="_ _9"> </span>line<span class="_ _9"> </span>segments,<span class="_ _8"> </span>endp<span class="_ _a"></span>oints<span class="_ _9"> </span>v<span class="_ _1"></span>ariance,<span class="_ _9"> </span>etc.,<span class="_ _9"> </span>for<span class="_ _9"> </span>both</div><div class="t m0 x7 h6 y5a ff7 fs4 fc0 sc0 ls0 ws0">the<span class="_ _8"> </span>stereo<span class="_ _8"> </span>and<span class="_ _8"> </span>frame-to-frame<span class="_ _8"> </span>tracking,<span class="_ _8"> </span>hence<span class="_ _8"> </span>b<span class="_ _a"></span>ecoming<span class="_ _8"> </span>a</div><div class="t m0 x7 h6 y3a ff7 fs4 fc0 sc0 ls0 ws0">more<span class="_ _9"> </span>robust<span class="_ _9"> </span>approac<span class="_ _1"></span>h<span class="_ _9"> </span>to<span class="_ _9"> </span>p<span class="_ _a"></span>oint-and-line<span class="_ _8"> </span>SLAM.</div><div class="c xc yda w2 ha"><div class="t m0 x10 hb ydb ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">N</span><span class="fc2 sc0">e</span><span class="fc2 sc0">w Fr</span><span class="fc2 sc0">ame</span></div><div class="t m0 x11 hb ydc ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">is it a</span><span class="fc2 sc0"> KF?</span></div><div class="t m0 x7 hb ydd ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">F</span><span class="fc2 sc0">eature </span></div><div class="t m0 x11 hb yde ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">Extraction</span></div><div class="t m0 x2 hb ydf ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">S</span><span class="fc2 sc0">tereo</span></div><div class="t m0 x12 hb ye0 ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">Matc</span><span class="fc2 sc0">hing</span></div><div class="t m0 x13 hb ye1 ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">Frame-to-fr</span><span class="fc2 sc0">ame</span></div><div class="t m0 x14 hb ye2 ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">T</span><span class="_ _f"></span><span class="fc2 sc0">rac</span><span class="fc2 sc0">king</span></div><div class="t m0 x7 hb ye3 ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">Motion</span></div><div class="t m0 x11 hb ye4 ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">Es</span><span class="fc2 sc0">timat</span><span class="fc2 sc0">ion</span></div><div class="t m0 x15 hc ye5 ffe fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">Ster</span><span class="fc2 sc0">eo V</span><span class="fc2 sc0">isual Odome</span><span class="fc2 sc0">try</span></div><div class="t m0 x8 hb ye6 ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">Searc</span><span class="fc2 sc0">h ne</span><span class="_ _f"></span><span class="fc2 sc0">w </span></div><div class="t m0 x16 hb ye7 ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">matc</span><span class="fc2 sc0">hes with </span></div><div class="t m0 x8 hb ye8 ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">other KFs in </span></div><div class="t m0 x17 hb ye9 ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">the map</span></div><div class="t m0 x18 hc yea ffe fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">Local Mapping</span></div><div class="t m0 x19 hb yeb ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">Get visual</span><span class="fc2 sc0"> </span></div><div class="t m0 x19 hb yec ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">descr</span><span class="fc2 sc0">iptor</span></div><div class="t m0 x1a hb yed ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">Quer</span><span class="fc2 sc0">y</span></div><div class="t m0 x1b hb yee ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">bag-of-</span><span class="fc2 sc0">w</span><span class="fc2 sc0">ords</span></div><div class="t m0 x1c hb yef ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">Compute</span></div><div class="t m0 x1d hb yf0 ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">pose c</span><span class="fc2 sc0">hang</span><span class="fc2 sc0">e</span></div><div class="t m0 x1e hb yf1 ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">Loop</span></div><div class="t m0 x19 hb yf2 ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">cor</span><span class="fc2 sc0">rection</span></div><div class="t m0 x1f hc yf3 ffe fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">Loop Closing</span></div><div class="t m0 x20 hb yf4 ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">Inser</span><span class="fc2 sc0">t</span></div><div class="t m0 x17 hb yf5 ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">ne</span><span class="fc2 sc0">w KF</span></div><div class="t m0 x17 hb yf6 ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">P</span><span class="fc2 sc0">er</span><span class="fc2 sc0">f</span><span class="fc2 sc0">or</span><span class="fc2 sc0">m</span></div><div class="t m0 x21 hb yf7 ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">local B</span><span class="_ _1"></span><span class="fc2 sc0">A</span></div><div class="t m0 x22 hc yf8 ffe fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">Map</span></div><div class="t m0 x23 hb yf9 ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">K</span><span class="fc2 sc0">e</span><span class="_ _f"></span><span class="fc2 sc0">yframes</span></div><div class="t m0 x24 hb yfa ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">Co</span><span class="fc2 sc0">visibil</span><span class="fc2 sc0">ity</span></div><div class="t m0 x25 hb yfb ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">g</span><span class="fc2 sc0">raph</span></div><div class="t m0 x26 hb yfc ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">Spanning tree</span></div><div class="t m0 x25 hb yfd ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">Graph</span></div><div class="t m0 x27 hb yfe ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">3D Line</span></div><div class="t m0 x28 hb yff ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">segment</span><span class="fc2 sc0">s</span></div><div class="t m0 x28 hb y100 ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">3D points</span></div><div class="t m0 x29 hb y101 ffd fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">Landmarks</span></div><div class="t m0 x2a hd y102 fff fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">y</span><span class="fc2 sc0">es</span></div><div class="t m0 x2b hd y103 fff fs7 fc0 sc0 ls0 ws0"><span class="fc2 sc0">no</span></div></div><div class="t m0 xc h7 y104 ff9 fs5 fc0 sc0 ls0 ws0">Figure<span class="_ _7"> </span>2.<span class="_ _e"> </span>Scheme<span class="_ _7"> </span>of<span class="_ _7"> </span>the<span class="_ _8"> </span>stereo<span class="_ _7"> </span>PL-SLAM<span class="_ _7"> </span>system.</div><div class="t m0 x2c h6 y105 ff6 fs4 fc0 sc0 ls0 ws0">I<span class="_ _a"></span>I<span class="_ _a"></span>I.<span class="_ _e"> </span>PL-SLAM<span class="_ _9"> </span>Over<span class="_ _4"></span>view</div><div class="t m0 xd h6 y106 ff7 fs4 fc0 sc0 ls0 ws0">The<span class="_ _7"> </span>general<span class="_ _10"> </span>structure<span class="_ _7"> </span>of<span class="_ _7"> </span>the<span class="_ _7"> </span>PL-SLAM<span class="_ _7"> </span>system<span class="_ _7"> </span>proposed</div><div class="t m0 xc h6 y107 ff7 fs4 fc0 sc0 ls0 ws0">here<span class="_"> </span>is<span class="_ _d"> </span>depicted<span class="_"> </span>in<span class="_ _d"> </span>Figure<span class="_"> </span>2,<span class="_"> </span>and<span class="_ _d"> </span>its<span class="_"> </span>main<span class="_ _d"> </span>mo<span class="_ _a"></span>dules<span class="_"> </span>are</div><div class="t m0 xc h6 y108 ff7 fs4 fc0 sc0 ls0 ws0">describ<span class="_ _a"></span>ed<span class="_"> </span>in<span class="_ _6"> </span>the<span class="_"> </span>follo<span class="_ _1"></span>wing<span class="_"> </span>sections.<span class="_ _d"> </span>As<span class="_"> </span>it<span class="_ _d"> </span>is<span class="_"> </span>common<span class="_ _d"> </span>to</div><div class="t m0 xc h6 y109 ff7 fs4 fc0 sc0 ls0 ws0">other<span class="_"> </span>SLAM<span class="_"> </span>systems<span class="_"> </span>(being<span class="_"> </span>ORB-SLAM<span class="_"> </span>[13]<span class="_"> </span>the<span class="_"> </span>most</div><div class="t m0 xc h6 y10a ff7 fs4 fc0 sc0 ls0 ws0">p<span class="_ _a"></span>opular<span class="_ _18"> </span>metho<span class="_ _a"></span>d<span class="_ _18"> </span>now<span class="_ _1"></span>adays),<span class="_"> </span>our<span class="_ _18"> </span>prop<span class="_ _a"></span>osal<span class="_ _18"> </span>is<span class="_ _18"> </span>also<span class="_ _18"> </span>based</div><div class="t m0 xc h6 y10b ff7 fs4 fc0 sc0 ls0 ws0">on<span class="_ _8"> </span>three<span class="_ _8"> </span>di&#64256;erent<span class="_ _7"> </span>threads:<span class="_ _9"> </span><span class="ff8">visual<span class="_ _8"> </span>o<span class="_ _4"></span>dometry<span class="ff7">,<span class="_ _9"> </span></span>lo<span class="_ _4"></span>c<span class="_ _1"></span>al<span class="_ _9"> </span>mapping<span class="ff7">,</span></span></div><div class="t m0 xc h6 y10c ff7 fs4 fc0 sc0 ls0 ws0">and<span class="_ _d"> </span><span class="ff8">lo<span class="_ _1"></span>op<span class="_ _c"> </span>closur<span class="_ _1"></span>e<span class="ff7">.<span class="_"> </span>This<span class="_ _d"> </span>e&#64259;cient<span class="_ _6"> </span>distribution<span class="_"> </span>allo<span class="_ _1"></span>ws<span class="_"> </span>for<span class="_ _d"> </span>a</span></span></div><div class="t m0 xc h6 y10d ff7 fs4 fc0 sc0 ls0 ws0">con<span class="_ _1"></span>tinuous<span class="_ _18"> </span>tracking<span class="_ _19"> </span>of<span class="_ _e"> </span>the<span class="_ _e"> </span>V<span class="_ _1"></span>O<span class="_ _e"> </span>mo<span class="_ _a"></span>dule<span class="_ _e"> </span>while<span class="_ _18"> </span>the<span class="_ _e"> </span>lo<span class="_ _a"></span>cal</div><div class="t m0 xc h6 y10e ff7 fs4 fc0 sc0 ls0 ws0">mapping<span class="_ _6"> </span>and<span class="_ _6"> </span>the<span class="_ _6"> </span>lo<span class="_ _2"></span>op<span class="_ _6"> </span>closure<span class="_ _6"> </span>ones<span class="_ _6"> </span>are<span class="_ _d"> </span>pro<span class="_ _a"></span>cessed<span class="_ _6"> </span>in<span class="_ _6"> </span>the</div><div class="t m0 xc h6 y10f ff7 fs4 fc0 sc0 ls0 ws0">bac<span class="_ _1"></span>kground<span class="_ _9"> </span>only<span class="_ _9"> </span>when<span class="_ _9"> </span>a<span class="_ _9"> </span>new<span class="_ _9"> </span>keyframe<span class="_ _8"> </span>is<span class="_ _9"> </span>inserted.</div><div class="t m0 xd h6 y110 ff10 fs4 fc0 sc0 ls0 ws0">Map.<span class="_ _9"> </span><span class="ff7">The<span class="_ _9"> </span>map<span class="_ _9"> </span>consists<span class="_ _8"> </span>of<span class="_ _9"> </span>i)<span class="_ _9"> </span>a<span class="_ _9"> </span>set<span class="_ _9"> </span>of<span class="_ _9"> </span>k<span class="_ _1"></span>eyframes<span class="_ _9"> </span>(KF<span class="_ _4"></span>s),</span></div><div class="t m0 xc h6 y111 ff7 fs4 fc0 sc0 ls0 ws0">ii)<span class="_ _d"> </span><span class="fc2 sc0">the</span><span class="_ _d"> </span><span class="fc2 sc0">detected</span><span class="_ _d"> </span><span class="fc2 sc0">3D</span><span class="_ _d"> </span><span class="fc2 sc0">land</span><span class="fc2 sc0">marks</span><span class="_ _d"> </span><span class="fc2 sc0">(b</span><span class="_ _a"></span><span class="fc2 sc0">oth</span><span class="_ _d"> </span><span class="fc2 sc0">k</span><span class="fc2 sc0">eyp</span><span class="fc2 sc0">oin</span><span class="fc2 sc0">ts</span><span class="_ _6"> </span><span class="fc2 sc0">and</span><span class="_"> </span><span class="fc2 sc0">line</span></div><div class="t m0 xc h6 y112 ff7 fs4 fc0 sc0 ls0 ws0"><span class="fc2 sc0">segmen</span><span class="_ _1"></span><span class="fc2 sc0">ts</span>),<span class="_ _8"> </span>iii)<span class="_ _7"> </span>a<span class="_ _8"> </span>co<span class="_ _1"></span>visibility<span class="_ _7"> </span>graph<span class="_ _8"> </span>and<span class="_ _7"> </span>iv)<span class="_ _7"> </span>a<span class="_ _8"> </span>spanning<span class="_ _7"> </span>tree.</div><div class="t m0 xd h6 y113 ff7 fs4 fc0 sc0 ls0 ws0">The<span class="_ _8"> </span>k<span class="_ _1"></span>eyframes<span class="_ _8"> </span>contain<span class="_ _8"> </span>the<span class="_ _8"> </span>observ<span class="_ _1"></span>ed<span class="_ _8"> </span>stereo<span class="_ _8"> </span>features<span class="_ _8"> </span>and</div><div class="t m0 xc h6 y114 ff7 fs4 fc0 sc0 ls0 ws0">their<span class="_ _9"> </span>descriptors,<span class="_ _9"> </span>a<span class="_ _9"> </span>visual<span class="_ _9"> </span>descriptor<span class="_ _9"> </span>of<span class="_ _9"> </span>the<span class="_ _8"> </span>corresp<span class="_ _2"></span>onding</div><div class="t m0 xc h6 y115 ff7 fs4 fc0 sc0 ls0 ws0">left<span class="_ _6"> </span>image<span class="_ _6"> </span>computed<span class="_ _6"> </span>through<span class="_ _6"> </span>a<span class="_ _d"> </span>visual<span class="_ _6"> </span>vocabulary<span class="_ _6"> </span>as<span class="_ _6"> </span>ex-</div><div class="t m0 xc h6 y116 ff7 fs4 fc0 sc0 ls0 ws0">plained<span class="_ _9"> </span>later<span class="_ _9"> </span>in<span class="_ _3"> </span>Section<span class="_ _9"> </span>VI-A,<span class="_ _9"> </span>and<span class="_ _3"> </span>the<span class="_ _9"> </span>information<span class="_ _9"> </span>of<span class="_ _3"> </span>the</div><div class="t m0 xc h6 y117 ff7 fs4 fc0 sc0 ls0 ws0">3D<span class="_ _9"> </span>camera<span class="_ _9"> </span>pose.</div><div class="t m0 xd h6 y118 ff7 fs4 fc0 sc0 ls0 ws0">Regarding<span class="_"> </span>the<span class="_ _19"> </span>landmarks,<span class="_ _18"> </span>we<span class="_"> </span>store<span class="_"> </span>the<span class="_"> </span>list<span class="_ _18"> </span>of<span class="_"> </span>obser-</div><div class="t m0 xc h6 y119 ff7 fs4 fc0 sc0 ls0 ws0">v<span class="_ _1"></span>ations<span class="_"> </span>and<span class="_"> </span>the<span class="_ _d"> </span>most<span class="_"> </span>representativ<span class="_ _1"></span>e<span class="_"> </span>descriptor<span class="_"> </span>for<span class="_"> </span>eac<span class="_ _1"></span>h</div><div class="t m0 xc h6 y11a ff7 fs4 fc0 sc0 ls0 ws0">detected<span class="_ _b"> </span>landmark.<span class="_ _b"> </span><span class="fc2 sc0">Besides,</span><span class="_ _b"> </span><span class="fc2 sc0">sp</span><span class="fc2 sc0">eci&#64257;cally</span><span class="_ _b"> </span><span class="fc2 sc0">f</span><span class="fc2 sc0">or</span><span class="_ _b"> </span><span class="fc2 sc0">p</span><span class="_ _a"></span><span class="fc2 sc0">oin</span><span class="fc2 sc0">ts,</span><span class="_ _b"> </span><span class="fc2 sc0">w</span><span class="_ _1"></span><span class="fc2 sc0">e</span></div><div class="t m0 xc h6 y11b ff7 fs4 fc0 sc0 ls0 ws0"><span class="fc2 sc0">also</span><span class="_ _18"> </span><span class="fc2 sc0">k</span><span class="fc2 sc0">eep</span><span class="_"> </span><span class="fc2 sc0">its</span><span class="_ _18"> </span><span class="fc2 sc0">estimated</span><span class="_ _e"> </span><span class="fc2 sc0">3D</span><span class="_ _18"> </span><span class="fc2 sc0">p</span><span class="_ _a"></span><span class="fc2 sc0">osition</span><span class="_ _18"> </span><span class="fc2 sc0">while,</span><span class="_ _18"> </span><span class="fc2 sc0">for</span><span class="_ _e"> </span><span class="fc2 sc0">the</span><span class="_ _18"> </span><span class="fc2 sc0">l</span><span class="fc2 sc0">ine</span></div><div class="t m0 xc h6 y11c ff7 fs4 fc0 sc0 ls0 ws0"><span class="fc2 sc0">segmen</span><span class="_ _1"></span><span class="fc2 sc0">ts,</span><span class="_ _9"> </span><span class="fc2 sc0">w</span><span class="fc2 sc0">e</span><span class="_ _8"> </span><span class="fc2 sc0">k</span><span class="fc2 sc0">eep</span><span class="_ _9"> </span><span class="fc2 sc0">b</span><span class="fc2 sc0">oth</span><span class="_ _9"> </span><span class="fc2 sc0">their</span><span class="_ _9"> </span><span class="fc2 sc0">direction</span><span class="_ _9"> </span><span class="fc2 sc0">and</span><span class="_ _8"> </span><span class="fc2 sc0">the</span><span class="_ _9"> </span><span class="fc2 sc0">estimated</span></div><div class="t m0 xc h6 y11d ff7 fs4 fc0 sc0 ls0 ws0"><span class="fc2 sc0">3D</span><span class="_ _9"> </span><span class="fc2 sc0">co</span><span class="fc2 sc0">ordinates</span><span class="_ _9"> </span><span class="fc2 sc0">of</span><span class="_ _9"> </span><span class="fc2 sc0">their</span><span class="_ _9"> </span><span class="fc2 sc0">endp</span><span class="_ _a"></span><span class="fc2 sc0">oin</span><span class="fc2 sc0">ts.</span></div><div class="t m0 xd h6 y11e ff7 fs4 fc0 sc0 ls0 ws0">Finally<span class="_ _4"></span>,<span class="_ _3"> </span>the<span class="_ _9"> </span>covisibilit<span class="_ _1"></span>y<span class="_ _3"> </span>information,<span class="_ _3"> </span>as<span class="_ _3"> </span>in<span class="_ _3"> </span>[38],<span class="_ _9"> </span>is<span class="_ _3"> </span>mo<span class="_ _a"></span>d-</div><div class="t m0 xc h6 y11f ff7 fs4 fc0 sc0 ls0 ws0">eled<span class="_ _d"> </span>by<span class="_ _6"> </span>a<span class="_ _d"> </span>graph:<span class="_ _d"> </span>each<span class="_ _6"> </span>no<span class="_ _a"></span>de<span class="_"> </span>represen<span class="_ _1"></span>ts<span class="_ _d"> </span>a<span class="_ _d"> </span>KF,<span class="_ _d"> </span>and<span class="_"> </span>edges</div><div class="t m0 xc h6 y120 ff7 fs4 fc0 sc0 ls0 ws0">b<span class="_ _a"></span>et<span class="_ _f"></span>w<span class="_ _1"></span>een<span class="_"> </span>KF<span class="_ _4"></span>s<span class="_ _6"> </span>are<span class="_"> </span>created<span class="_ _6"> </span>only<span class="_ _d"> </span>if<span class="_ _d"> </span>they<span class="_"> </span>share<span class="_ _6"> </span>a<span class="_ _d"> </span>minimum</div><div class="t m0 xc h6 y121 ff7 fs4 fc0 sc0 ls0 ws0">n<span class="_ _1"></span>umber<span class="_ _e"> </span>of<span class="_ _18"> </span>landmarks,<span class="_ _18"> </span>which<span class="_ _19"> </span>in<span class="_ _18"> </span>this<span class="_ _e"> </span>w<span class="_ _f"></span>ork<span class="_ _18"> </span>is<span class="_ _18"> </span>set<span class="_ _18"> </span>to<span class="_ _18"> </span>20</div><div class="t m0 xc h6 y122 ff7 fs4 fc0 sc0 ls0 ws0">landmarks<span class="_ _7"> </span>(see<span class="_ _7"> </span>Figure<span class="_ _7"> </span>3<span class="_ _7"> </span>for<span class="_ _8"> </span>an<span class="_ _10"> </span>example),<span class="_ _8"> </span>allo<span class="_ _1"></span>wing<span class="_ _7"> </span>for<span class="_ _7"> </span>real-</div><div class="t m0 xc h6 y123 ff7 fs4 fc0 sc0 ls0 ws0">time<span class="_ _9"> </span>bundle<span class="_ _9"> </span>adjustmen<span class="_ _1"></span>t<span class="_ _9"> </span>along<span class="_ _9"> </span>the<span class="_ _9"> </span>lo<span class="_ _a"></span>cal<span class="_ _9"> </span>map.</div><div class="t m0 xd h6 y36 ff7 fs4 fc0 sc0 ls0 ws0">Similarly<span class="_ _4"></span>,<span class="_ _b"> </span>in<span class="_ _b"> </span>order<span class="_ _b"> </span>to<span class="_ _b"> </span>p<span class="_ _a"></span>erform<span class="_ _b"> </span>a<span class="_ _b"> </span>faster<span class="_ _0"> </span>loop<span class="_ _b"> </span>closure</div><div class="t m0 xc h6 y59 ff7 fs4 fc0 sc0 ls0 ws0">optimization,<span class="_ _6"> </span>we<span class="_ _6"> </span>also<span class="_ _6"> </span>form<span class="_ _d"> </span>the<span class="_ _6"> </span>so-called<span class="_ _d"> </span><span class="ff8">essential<span class="_ _6"> </span>gr<span class="_ _f"></span>aph<span class="ff7">,</span></span></div><div class="t m0 xc h6 y5a ff7 fs4 fc0 sc0 ls0 ws0">whic<span class="_ _1"></span>h<span class="_ _9"> </span>is<span class="_ _9"> </span>less<span class="_ _9"> </span>dense<span class="_ _9"> </span>than<span class="_ _8"> </span>the<span class="_ _9"> </span>covisibilit<span class="_ _1"></span>y<span class="_ _9"> </span>graph<span class="_ _9"> </span>because<span class="_ _9"> </span>an</div><div class="t m0 xc h6 y3a ff7 fs4 fc0 sc0 ls0 ws0">edge<span class="_ _6"> </span>b<span class="_ _a"></span>etw<span class="_ _1"></span>een<span class="_ _6"> </span>tw<span class="_ _1"></span>o<span class="_ _6"> </span>KF<span class="_ _1"></span>s<span class="_ _6"> </span>is<span class="_ _6"> </span>created<span class="_ _6"> </span>when<span class="_ _6"> </span>they<span class="_ _6"> </span>share<span class="_ _d"> </span>more</div><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a></div><div class="pi" data-data='{"ctm":[1.568627,0.000000,0.000000,1.568627,0.000000,0.000000]}'></div></div><div id="pf4" class="pf w0 h0" data-page-no="4"><div class="pc pc4 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="/image.php?url=https://csdnimg.cn/release/download_crawler_static/89541504/bg4.jpg"><div class="t m0 x1 h2 y1 ff1 fs0 fc0 sc0 ls0 ws0">4</div><div class="t m0 x7 h6 y5c ff7 fs4 fc0 sc0 ls0 ws0">than<span class="_ _19"> </span>100<span class="_ _18"> </span>landmark<span class="_ _18"> </span>observ<span class="_ _1"></span>ations.<span class="_ _19"> </span>Finally<span class="_ _1"></span>,<span class="_"> </span>the<span class="_ _18"> </span>map<span class="_ _18"> </span>also</div><div class="t m0 x7 h6 y5d ff7 fs4 fc0 sc0 ls0 ws0">con<span class="_ _1"></span>tains<span class="_ _8"> </span>a<span class="_ _7"> </span>spanning<span class="_ _7"> </span>tree,<span class="_ _7"> </span>which<span class="_ _7"> </span>is<span class="_ _7"> </span>the<span class="_ _8"> </span>minim<span class="_ _1"></span>um<span class="_ _7"> </span>connected</div><div class="t m0 x7 h6 y5e ff7 fs4 fc0 sc0 ls0 ws0">represen<span class="_ _1"></span>tation<span class="_ _9"> </span>of<span class="_ _9"> </span>a<span class="_ _9"> </span>graph<span class="_ _9"> </span>that<span class="_ _9"> </span>includes<span class="_ _9"> </span>all<span class="_ _9"> </span>the<span class="_ _9"> </span>KF<span class="_ _4"></span>s.</div><div class="t m0 x6 h6 y5f ff10 fs4 fc0 sc0 ls0 ws0">F<span class="_ _4"></span>eature<span class="_ _14"> </span>T<span class="_ _4"></span>rac<span class="_ _1"></span>king.<span class="_ _12"> </span><span class="ff7">W<span class="_ _4"></span>e<span class="_ _20"> </span>p<span class="_ _a"></span>erform<span class="_ _20"> </span>feature<span class="_ _20"> </span>tracking</span></div><div class="t m0 x7 h6 y60 ff7 fs4 fc0 sc0 ls0 ws0">through<span class="_"> </span>the<span class="_ _d"> </span>stereo<span class="_"> </span>visual<span class="_"> </span>odometry<span class="_"> </span>algorithm<span class="_"> </span>from<span class="_ _d"> </span>our</div><div class="t m0 x7 h6 y61 ff7 fs4 fc0 sc0 ls0 ws0">previous<span class="_ _18"> </span>work<span class="_ _18"> </span>[20].<span class="_ _e"> </span>In<span class="_ _e"> </span>a<span class="_ _18"> </span>nutshell,<span class="_ _18"> </span>we<span class="_ _18"> </span>track<span class="_ _19"> </span>image<span class="_ _e"> </span>fea-</div><div class="t m0 x7 h6 y62 ff7 fs4 fc0 sc0 ls0 ws0">tures<span class="_ _18"> </span>(p<span class="_ _a"></span>oints<span class="_"> </span>and<span class="_ _e"> </span>segmen<span class="_ _f"></span>ts)<span class="_ _18"> </span>from<span class="_ _18"> </span>a<span class="_ _18"> </span>sequence<span class="_ _e"> </span>of<span class="_ _18"> </span>stereo</div><div class="t m0 x7 h6 y63 ff7 fs4 fc0 sc0 ls0 ws0">frames<span class="_ _7"> </span>and<span class="_ _7"> </span>compute<span class="_ _10"> </span>their<span class="_ _7"> </span>3D<span class="_ _7"> </span>p<span class="_ _a"></span>osition<span class="_ _7"> </span>and<span class="_ _7"> </span>their<span class="_ _7"> </span>asso<span class="_ _a"></span>ciated</div><div class="t m0 x7 h6 y64 ff7 fs4 fc0 sc0 ls0 ws0">uncertain<span class="_ _1"></span>ty<span class="_ _6"> </span>represented<span class="_ _6"> </span>by<span class="_ _6"> </span>cov<span class="_ _1"></span>ariance<span class="_ _6"> </span>matrices.<span class="_"> </span>The<span class="_ _6"> </span>3D</div><div class="t m0 x7 h6 y65 ff7 fs4 fc0 sc0 ls0 ws0">landmarks<span class="_ _7"> </span>are<span class="_ _7"> </span>then<span class="_ _7"> </span>pro<span class="_ _a"></span>jected<span class="_ _7"> </span>to<span class="_ _7"> </span>the<span class="_ _7"> </span>new<span class="_ _7"> </span>camera<span class="_ _7"> </span>p<span class="_ _a"></span>ose,<span class="_ _7"> </span>and</div><div class="t m0 x7 h6 y6 ff7 fs4 fc0 sc0 ls0 ws0">the<span class="_ _10"> </span>pro<span class="_ _a"></span>jection<span class="_ _7"> </span>errors<span class="_ _10"> </span>are<span class="_ _7"> </span>minimized<span class="_ _7"> </span>in<span class="_ _10"> </span>order<span class="_ _7"> </span>to<span class="_ _10"> </span>obtain<span class="_ _7"> </span>b<span class="_ _a"></span>oth</div><div class="t m0 x7 h6 y66 ff7 fs4 fc0 sc0 ls0 ws0">the<span class="_ _9"> </span>camera<span class="_ _9"> </span>p<span class="_ _a"></span>ose<span class="_ _3"> </span>incremen<span class="_ _1"></span>t<span class="_ _3"> </span>and<span class="_ _9"> </span>the<span class="_ _9"> </span>cov<span class="_ _4"></span>ariance<span class="_ _3"> </span>asso<span class="_ _a"></span>ciated</div><div class="t m0 x7 h6 y67 ff7 fs4 fc0 sc0 ls0 ws0">to<span class="_"> </span>suc<span class="_ _1"></span>h<span class="_"> </span>estimation.<span class="_"> </span>This<span class="_"> </span>pro<span class="_ _a"></span>cess<span class="_"> </span>is<span class="_"> </span>rep<span class="_ _a"></span>eated<span class="_"> </span>every<span class="_"> </span>new</div><div class="t m0 x7 h6 ybb ff7 fs4 fc0 sc0 ls0 ws0">frame,<span class="_ _8"> </span>p<span class="_ _a"></span>erforming<span class="_ _9"> </span>simply<span class="_ _8"> </span>frame<span class="_ _8"> </span>to<span class="_ _9"> </span>frame<span class="_ _8"> </span>VO,<span class="_ _8"> </span>un<span class="_ _1"></span>til<span class="_ _9"> </span>a<span class="_ _8"> </span>new</div><div class="t m0 x7 h6 ybc ff7 fs4 fc0 sc0 ls0 ws0">KF<span class="_ _3"> </span>is<span class="_ _9"> </span>inserted<span class="_ _3"> </span>to<span class="_ _3"> </span>the<span class="_ _3"> </span>map.<span class="_ _9"> </span>F<span class="_ _1"></span>urther<span class="_ _9"> </span>discussion<span class="_ _3"> </span>ab<span class="_ _a"></span>out<span class="_ _3"> </span>this</div><div class="t m0 x7 h6 yc ff7 fs4 fc0 sc0 ls0 ws0">feature<span class="_ _6"> </span>trac<span class="_ _f"></span>king<span class="_ _6"> </span>pro<span class="_ _a"></span>cedure<span class="_ _6"> </span>will<span class="_ _6"> </span>b<span class="_ _a"></span>e<span class="_ _6"> </span>formally<span class="_ _6"> </span>addressed<span class="_ _6"> </span>in</div><div class="t m0 x7 h6 ybd ff7 fs4 fc0 sc0 ls0 ws0">Section<span class="_ _18"> </span>IV.<span class="_ _e"> </span>Once<span class="_ _e"> </span>a<span class="_ _e"> </span>KF<span class="_ _e"> </span>is<span class="_ _e"> </span>inserted<span class="_ _e"> </span>in<span class="_ _f"></span>to<span class="_ _18"> </span>the<span class="_ _e"> </span>map,<span class="_ _e"> </span>tw<span class="_ _1"></span>o</div><div class="t m0 x7 h6 ybe ff7 fs4 fc0 sc0 ls0 ws0">pro<span class="_ _a"></span>cedures<span class="_"> </span>are<span class="_"> </span>run<span class="_"> </span>in<span class="_"> </span>parallel:<span class="_ _19"> </span>lo<span class="_ _a"></span>cal<span class="_ _19"> </span>mapping<span class="_"> </span>and<span class="_ _19"> </span>lo<span class="_ _a"></span>op</div><div class="t m0 x7 h6 ybf ff7 fs4 fc0 sc0 ls0 ws0">closure<span class="_ _9"> </span>detection.</div><div class="t m0 x6 h6 yc0 ff10 fs4 fc0 sc0 ls0 ws0">Lo<span class="_ _a"></span>cal<span class="_ _c"> </span>Mapping.<span class="_ _6"> </span><span class="ff7">The<span class="_ _6"> </span>lo<span class="_ _a"></span>cal<span class="_ _6"> </span>mapping<span class="_ _d"> </span>pro<span class="_ _a"></span>cedure<span class="_ _6"> </span>lo<span class="_ _a"></span>oks</span></div><div class="t m0 x7 h6 y12 ff7 fs4 fc0 sc0 ls0 ws0">for<span class="_ _8"> </span>new<span class="_ _8"> </span>feature<span class="_ _8"> </span>correspondences<span class="_ _8"> </span>b<span class="_ _a"></span>etw<span class="_ _1"></span>een<span class="_ _8"> </span>the<span class="_ _8"> </span>new<span class="_ _8"> </span>KF,<span class="_ _8"> </span>the</div><div class="t m0 x7 h6 yc1 ff7 fs4 fc0 sc0 ls0 ws0">last<span class="_ _6"> </span>one<span class="_ _3"> </span>and<span class="_ _6"> </span>those<span class="_ _6"> </span>connected<span class="_ _3"> </span>to<span class="_ _6"> </span>the<span class="_ _6"> </span>last<span class="_ _3"> </span>one<span class="_ _6"> </span>in<span class="_ _6"> </span>the<span class="_ _3"> </span>cov-</div><div class="t m0 x7 h6 yc2 ff7 fs4 fc0 sc0 ls0 ws0">isibilit<span class="_ _1"></span>y<span class="_ _9"> </span>graph.<span class="_ _9"> </span>This<span class="_ _9"> </span>wa<span class="_ _1"></span>y<span class="_ _4"></span>,<span class="_ _9"> </span>we<span class="_ _8"> </span>build<span class="_ _9"> </span>the<span class="_ _9"> </span>so-called<span class="_ _9"> </span><span class="ff8">lo<span class="_ _1"></span>c<span class="_ _1"></span>al<span class="_ _9"> </span>map</span></div><div class="t m0 x7 h6 yc3 ff7 fs4 fc0 sc0 ls0 ws0">of<span class="_ _3"> </span>the<span class="_ _9"> </span>current<span class="_ _9"> </span>KF,<span class="_ _3"> </span>which<span class="_ _9"> </span>includes<span class="_ _3"> </span>all<span class="_ _3"> </span>the<span class="_ _3"> </span>KF<span class="_ _4"></span>s<span class="_ _3"> </span>that<span class="_ _3"> </span>share</div><div class="t m0 x7 h6 yc4 ff7 fs4 fc0 sc0 ls0 ws0">at<span class="_ _8"> </span>least<span class="_ _9"> </span>20<span class="_ _8"> </span>landmark<span class="_ _8"> </span>observ<span class="_ _1"></span>ations<span class="_ _8"> </span>with<span class="_ _9"> </span>the<span class="_ _8"> </span>curren<span class="_ _f"></span>t<span class="_ _8"> </span>one<span class="_ _9"> </span>as</div><div class="t m0 x7 h6 y18 ff7 fs4 fc0 sc0 ls0 ws0">w<span class="_ _1"></span>ell<span class="_ _d"> </span>as<span class="_ _6"> </span>all<span class="_ _d"> </span>the<span class="_ _6"> </span>landmarks<span class="_ _d"> </span>observ<span class="_ _1"></span>ed<span class="_ _d"> </span>by<span class="_ _6"> </span>them.<span class="_ _6"> </span>Finally<span class="_ _4"></span>,<span class="_ _6"> </span>an</div><div class="t m0 x7 h6 yc5 ff7 fs4 fc0 sc0 ls0 ws0">optimization<span class="_ _8"> </span>of<span class="_ _8"> </span>all<span class="_ _8"> </span>the<span class="_ _8"> </span>elemen<span class="_ _1"></span>ts<span class="_ _8"> </span>within<span class="_ _8"> </span>the<span class="_ _8"> </span>lo<span class="_ _a"></span>cal<span class="_ _8"> </span>map<span class="_ _8"> </span>(KF</div><div class="t m0 x7 h6 yc6 ff7 fs4 fc0 sc0 ls0 ws0">p<span class="_ _a"></span>oses<span class="_ _6"> </span>and<span class="_ _3"> </span>landmarks<span class="_ _6"> </span>positions)<span class="_ _6"> </span>is<span class="_ _6"> </span>performed.<span class="_ _6"> </span>A<span class="_ _3"> </span>detailed</div><div class="t m0 x7 h6 yc7 ff7 fs4 fc0 sc0 ls0 ws0">description<span class="_ _9"> </span>of<span class="_ _3"> </span>this<span class="_ _9"> </span>pro<span class="_ _a"></span>cedure<span class="_ _3"> </span>will<span class="_ _9"> </span>b<span class="_ _a"></span>e<span class="_ _3"> </span>presen<span class="_ _1"></span>ted<span class="_ _3"> </span>in<span class="_ _9"> </span>Section</div><div class="t m0 x7 h6 yc8 ff7 fs4 fc0 sc0 ls0 ws0">V.</div><div class="t m0 x6 h6 y1e ff10 fs4 fc0 sc0 ls0 ws0">Lo<span class="_ _a"></span>op<span class="_ _e"> </span>Closure.<span class="_ _c"> </span><span class="ff7">In<span class="_"> </span>parallel<span class="_ _19"> </span>to<span class="_"> </span>lo<span class="_ _a"></span>cal<span class="_ _19"> </span>mapping,<span class="_"> </span>a<span class="_"> </span>lo<span class="_ _a"></span>op</span></div><div class="t m0 x7 h6 yc9 ff7 fs4 fc0 sc0 ls0 ws0">closure<span class="_ _e"> </span>detection<span class="_ _e"> </span>is<span class="_ _b"> </span>carried<span class="_ _e"> </span>out<span class="_ _e"> </span>by<span class="_ _18"> </span>extracting<span class="_ _b"> </span>a<span class="_ _18"> </span>visual</div><div class="t m0 x7 h6 yca ff7 fs4 fc0 sc0 ls0 ws0">descriptor<span class="_"> </span>for<span class="_"> </span>eac<span class="_ _1"></span>h<span class="_"> </span>image,<span class="_"> </span>based<span class="_"> </span>on<span class="_"> </span>a<span class="_"> </span>bag-of-w<span class="_ _1"></span>ords<span class="_"> </span>ap-</div><div class="t m0 x7 h6 ycb ff7 fs4 fc0 sc0 ls0 ws0">proac<span class="_ _1"></span>h,<span class="_ _3"> </span>as<span class="_ _3"> </span>will<span class="_ _3"> </span>b<span class="_ _a"></span>e<span class="_ _3"> </span>describ<span class="_ _a"></span>ed<span class="_ _3"> </span>in<span class="_ _3"> </span>Section<span class="_ _3"> </span>VI.<span class="_ _3"> </span>All<span class="_ _3"> </span>the<span class="_ _3"> </span>visual</div><div class="t m0 x7 h6 ycc ff7 fs4 fc0 sc0 ls0 ws0">descriptors<span class="_ _9"> </span>of<span class="_ _9"> </span>the<span class="_ _3"> </span>captured<span class="_ _9"> </span>frames<span class="_ _3"> </span>during<span class="_ _9"> </span>camera<span class="_ _9"> </span>motion</div><div class="t m0 x7 h6 ycd ff7 fs4 fc0 sc0 ls0 ws0">are<span class="_ _3"> </span>stored<span class="_ _3"> </span>in<span class="_ _3"> </span>a<span class="_ _3"> </span>database,<span class="_ _3"> </span>which<span class="_ _3"> </span>is<span class="_ _3"> </span>later<span class="_ _3"> </span>employ<span class="_ _1"></span>ed<span class="_ _3"> </span>to<span class="_ _3"> </span>&#64257;nd</div><div class="t m0 x7 h6 yce ff7 fs4 fc0 sc0 ls0 ws0">similar<span class="_"> </span>frames<span class="_"> </span>to<span class="_ _d"> </span>the<span class="_"> </span>curren<span class="_ _1"></span>t<span class="_"> </span>one.<span class="_"> </span>The<span class="_"> </span>best<span class="_"> </span>matc<span class="_ _f"></span>h<span class="_"> </span>will</div><div class="t m0 x7 h6 ycf ff7 fs4 fc0 sc0 ls0 ws0">b<span class="_ _a"></span>e<span class="_ _d"> </span>considered<span class="_ _d"> </span>a<span class="_ _d"> </span>lo<span class="_ _a"></span>op<span class="_"> </span>closure<span class="_ _6"> </span>candidate<span class="_ _d"> </span>only<span class="_"> </span>if<span class="_ _6"> </span>the<span class="_ _d"> </span>lo<span class="_ _a"></span>cal</div><div class="t m0 x7 h6 yd0 ff7 fs4 fc0 sc0 ls0 ws0">sequence<span class="_ _9"> </span>surrounding<span class="_ _9"> </span>this<span class="_ _9"> </span>KF<span class="_ _9"> </span>is<span class="_ _3"> </span>also<span class="_ _9"> </span>similar.<span class="_ _9"> </span>Finally<span class="_ _4"></span>,<span class="_ _3"> </span>the</div><div class="t m0 x7 h6 yd1 ff7 fs4 fc0 sc0 ls0 ws0">relativ<span class="_ _1"></span>e<span class="_ _7"> </span><span class="ff11">S<span class="_ _2"></span>E<span class="_ _2"></span><span class="ff12">(3)<span class="_ _10"> </span></span></span>transformation<span class="_ _10"> </span>b<span class="_ _a"></span>etw<span class="_ _1"></span>een<span class="_ _10"> </span>the<span class="_ _10"> </span>current<span class="_ _11"> </span>KF<span class="_ _10"> </span>and</div><div class="t m0 x7 h6 yd2 ff7 fs4 fc0 sc0 ls0 ws0">the<span class="_ _7"> </span>lo<span class="_ _a"></span>op<span class="_ _8"> </span>closure<span class="_ _7"> </span>candidate<span class="_ _8"> </span>is<span class="_ _7"> </span>estimated<span class="_ _8"> </span>so<span class="_ _7"> </span>that,<span class="_ _8"> </span>if<span class="_ _7"> </span>a<span class="_ _8"> </span>proper</div><div class="t m0 x7 h6 yd3 ff7 fs4 fc0 sc0 ls0 ws0">estimation<span class="_ _8"> </span>is<span class="_ _8"> </span>found,<span class="_ _8"> </span>all<span class="_ _7"> </span>the<span class="_ _8"> </span>KF<span class="_ _4"></span>s<span class="_ _8"> </span>p<span class="_ _a"></span>oses<span class="_ _8"> </span>inv<span class="_ _1"></span>olved<span class="_ _7"> </span>in<span class="_ _8"> </span>the<span class="_ _8"> </span>lo<span class="_ _a"></span>op</div><div class="t m0 x7 h6 yd4 ff7 fs4 fc0 sc0 ls0 ws0">are<span class="_ _6"> </span>corrected<span class="_ _6"> </span>through<span class="_ _6"> </span>a<span class="_ _d"> </span>p<span class="_ _a"></span>ose-graph<span class="_ _6"> </span>optimization<span class="_ _d"> </span>(PGO)</div><div class="t m0 x7 h6 yd5 ff7 fs4 fc0 sc0 ls0 ws0">pro<span class="_ _a"></span>cess.</div><div class="t m0 x6 h6 yd6 ff7 fs4 fc0 sc0 ls0 ws0">It<span class="_ _9"> </span>is<span class="_ _3"> </span>imp<span class="_ _a"></span>ortant<span class="_ _9"> </span>to<span class="_ _9"> </span>remark<span class="_ _3"> </span>that<span class="_ _9"> </span>the<span class="_ _3"> </span>stereo<span class="_ _9"> </span>visual<span class="_ _3"> </span>o<span class="_ _a"></span>dom-</div><div class="t m0 x7 h6 yd7 ff7 fs4 fc0 sc0 ls0 ws0">etry<span class="_ _3"> </span>system<span class="_ _3"> </span>runs<span class="_ _3"> </span>contin<span class="_ _1"></span>uously<span class="_ _3"> </span>at<span class="_ _3"> </span>every<span class="_ _9"> </span>frame<span class="_ _6"> </span>while<span class="_ _9"> </span>b<span class="_ _a"></span>oth</div><div class="t m0 x7 h6 yd8 ff7 fs4 fc0 sc0 ls0 ws0">the<span class="_ _3"> </span>lo<span class="_ _a"></span>cal<span class="_ _6"> </span>mapping<span class="_ _3"> </span>and<span class="_ _6"> </span>loop<span class="_ _6"> </span>closure<span class="_ _3"> </span>detection<span class="_ _3"> </span>pro<span class="_ _a"></span>cedures</div><div class="t m0 x7 h6 yd9 ff7 fs4 fc0 sc0 ls0 ws0">are<span class="_ _d"> </span>launched<span class="_ _6"> </span>in<span class="_ _d"> </span>background<span class="_ _6"> </span>(in<span class="_"> </span>separated<span class="_ _6"> </span>threads)<span class="_ _d"> </span>only</div><div class="t m0 x7 h6 y8b ff7 fs4 fc0 sc0 ls0 ws0">when<span class="_ _18"> </span>a<span class="_ _e"> </span>new<span class="_ _e"> </span>KF<span class="_ _e"> </span>is<span class="_ _18"> </span>inserted,<span class="_ _e"> </span>thus<span class="_ _18"> </span>allowing<span class="_ _18"> </span>our<span class="_ _18"> </span>system</div><div class="t m0 x7 h6 y8c ff7 fs4 fc0 sc0 ls0 ws0">to<span class="_ _19"> </span>reach<span class="_ _19"> </span>real-time<span class="_ _18"> </span>p<span class="_ _a"></span>erformance.<span class="_ _18"> </span>In<span class="_ _18"> </span>the<span class="_ _18"> </span>even<span class="_ _1"></span>t<span class="_ _18"> </span>of<span class="_ _18"> </span>a<span class="_ _18"> </span>new</div><div class="t m0 x7 h6 y8d ff7 fs4 fc0 sc0 ls0 ws0">k<span class="_ _1"></span>eyframe<span class="_ _b"> </span>being<span class="_ _b"> </span>inserted<span class="_ _18"> </span>in<span class="_ _e"> </span>the<span class="_ _b"> </span>system<span class="_ _18"> </span>while<span class="_ _b"> </span>the<span class="_ _18"> </span>lo<span class="_ _a"></span>cal</div><div class="t m0 x7 h6 y32 ff7 fs4 fc0 sc0 ls0 ws0">mapping<span class="_ _6"> </span>thread<span class="_ _6"> </span>is<span class="_ _6"> </span>still<span class="_ _d"> </span>b<span class="_ _a"></span>eing<span class="_ _6"> </span>pro<span class="_ _a"></span>cessed,<span class="_ _6"> </span>the<span class="_ _6"> </span>keyframe<span class="_ _6"> </span>is</div><div class="t m0 x7 h6 y56 ff7 fs4 fc0 sc0 ls0 ws0">temp<span class="_ _a"></span>orary<span class="_"> </span>stored<span class="_ _d"> </span>until<span class="_ _d"> </span>the<span class="_"> </span>map<span class="_"> </span>is<span class="_ _d"> </span>up<span class="_ _a"></span>dated<span class="_"> </span>and<span class="_ _d"> </span>then<span class="_"> </span>a</div><div class="t m0 x7 h6 y8e ff7 fs4 fc0 sc0 ls0 ws0">new<span class="_ _9"> </span>local<span class="_ _9"> </span>mapping<span class="_ _9"> </span>pro<span class="_ _a"></span>cess<span class="_ _9"> </span>is<span class="_ _9"> </span>launched.</div><div class="t m0 x6 h6 y36 ff7 fs4 fc0 sc0 ls0 ws0">These<span class="_ _9"> </span>mapping<span class="_ _9"> </span>and<span class="_ _8"> </span>lo<span class="_ _a"></span>op<span class="_ _9"> </span>closure<span class="_ _9"> </span>approaches<span class="_ _8"> </span>are<span class="_ _9"> </span>identi-</div><div class="t m0 x7 h6 y59 ff7 fs4 fc0 sc0 ls0 ws0">cal<span class="_ _6"> </span>to<span class="_ _6"> </span>the<span class="_ _6"> </span>ones<span class="_ _6"> </span>follow<span class="_ _1"></span>ed<span class="_ _6"> </span>in<span class="_ _6"> </span>ORB-SLAM,<span class="_ _6"> </span>b<span class="_ _a"></span>eing<span class="_ _d"> </span>aimed<span class="_ _6"> </span>to</div><div class="t m0 x7 h6 y5a ff7 fs4 fc0 sc0 ls0 ws0">reduce<span class="_"> </span>the<span class="_ _6"> </span>high<span class="_"> </span>computational<span class="_"> </span>burden<span class="_ _d"> </span>that<span class="_"> </span>general<span class="_ _d"> </span>BA</div><div class="t m0 x7 h6 y3a ff7 fs4 fc0 sc0 ls0 ws0">in<span class="_ _1"></span>volv<span class="_ _1"></span>es<span class="_ _9"> </span>(along<span class="_ _8"> </span>with<span class="_ _9"> </span>the<span class="_ _8"> </span>incorp<span class="_ _a"></span>oration<span class="_ _8"> </span>of<span class="_ _9"> </span>recen<span class="_ _1"></span>t<span class="_ _9"> </span>sparse<span class="_ _8"> </span>al-</div><div class="t m0 xc h7 y124 ff9 fs5 fc0 sc0 ls0 ws0">Figure<span class="_ _11"> </span>3.<span class="_ _e"> </span>Covisibilit<span class="_ _1"></span>y<span class="_ _11"> </span>graph<span class="_ _11"> </span>in<span class="_ _11"> </span>the<span class="_ _11"> </span>sequence<span class="_ _11"> </span><span class="ffa">lt-&#64257;rst<span class="_ _10"> </span></span>for<span class="_ _11"> </span>which<span class="_ _21"> </span>we<span class="_ _21"> </span>ha<span class="_ _f"></span>ve</div><div class="t m0 xc h7 y125 ff9 fs5 fc0 sc0 ls0 ws0">represented<span class="_ _10"> </span>the<span class="_ _8"> </span>edges<span class="_ _7"> </span>connecting<span class="_ _7"> </span>the<span class="_ _8"> </span>k<span class="_ _1"></span>eyframes<span class="_ _8"> </span>with<span class="_ _7"> </span>green<span class="_ _7"> </span>lines.</div><div class="t m0 xc h6 y126 ff7 fs4 fc0 sc0 ls0 ws0">gebra<span class="_ _10"> </span>tec<span class="_ _1"></span>hniques).<span class="_ _10"> </span>Within<span class="_ _10"> </span>the<span class="_ _10"> </span>BA<span class="_ _10"> </span>framework,<span class="_ _10"> </span>our<span class="_ _10"> </span>proposal</div><div class="t m0 xc h6 y127 ff7 fs4 fc0 sc0 ls0 ws0">b<span class="_ _a"></span>elongs<span class="_ _8"> </span>to<span class="_ _7"> </span>the<span class="_ _8"> </span>so-called<span class="_ _7"> </span><span class="ff8">r<span class="_ _1"></span>elative<span class="_ _8"> </span><span class="ff7">techniques<span class="_ _7"> </span>(e.g.<span class="_ _8"> </span>[39]&#8211;[41]),</span></span></div><div class="t m0 xc h6 y128 ff7 fs4 fc0 sc0 ls0 ws0">whic<span class="_ _1"></span>h<span class="_ _9"> </span>ha<span class="_ _1"></span>ve<span class="_ _8"> </span>gained<span class="_ _8"> </span>great<span class="_ _8"> </span>popularity<span class="_ _8"> </span>in<span class="_ _8"> </span>the<span class="_ _8"> </span>last<span class="_ _8"> </span>years<span class="_ _8"> </span>as<span class="_ _8"> </span>an</div><div class="t m0 xc h6 y129 ff7 fs4 fc0 sc0 ls0 ws0">alternativ<span class="_ _1"></span>e<span class="_ _9"> </span>to<span class="_ _8"> </span>the<span class="_ _8"> </span>more<span class="_ _8"> </span>costly<span class="_ _8"> </span><span class="ff8">glob<span class="_ _1"></span>al<span class="_ _3"> </span><span class="ff7">approaches<span class="_ _8"> </span>(e.g.<span class="_ _8"> </span>[24],</span></span></div><div class="t m0 xc h6 y12a ff7 fs4 fc0 sc0 ls0 ws0">[42]).</div><div class="t m0 x2d h6 y12b ff6 fs4 fc0 sc0 ls0 ws0">IV.<span class="_ _18"> </span>Fea<span class="_ _1"></span>ture<span class="_ _3"> </span>Tracking</div><div class="t m0 xd h6 y12c ff7 fs4 fc0 sc0 ls0 ws0">This<span class="_ _9"> </span>section<span class="_ _8"> </span>reviews<span class="_ _9"> </span>the<span class="_ _9"> </span>most<span class="_ _9"> </span>important<span class="_ _8"> </span>asp<span class="_ _a"></span>ects<span class="_ _9"> </span>of<span class="_ _9"> </span>our</div><div class="t m0 xc h6 y12d ff7 fs4 fc0 sc0 ls0 ws0">previous<span class="_ _9"> </span>work<span class="_ _8"> </span>[20],<span class="_ _3"> </span>whic<span class="_ _1"></span>h<span class="_ _3"> </span>deals<span class="_ _9"> </span>with<span class="_ _9"> </span>the<span class="_ _9"> </span>visual<span class="_ _9"> </span>o<span class="_ _a"></span>dometry</div><div class="t m0 xc h6 y12e ff7 fs4 fc0 sc0 ls0 ws0">estimation<span class="_ _0"> </span>betw<span class="_ _1"></span>een<span class="_ _0"> </span>consecutive<span class="_ _b"> </span>frames,<span class="_ _0"> </span>and<span class="_ _0"> </span>also<span class="_ _0"> </span>with</div><div class="t m0 xc h6 y12f ff7 fs4 fc0 sc0 ls0 ws0">the<span class="_"> </span>KF<span class="_ _18"> </span>decision<span class="_"> </span>p<span class="_ _2"></span>olicy<span class="_ _4"></span>.<span class="_ _19"> </span>Basically<span class="_ _4"></span>,<span class="_ _18"> </span>b<span class="_ _a"></span>oth<span class="_ _19"> </span>p<span class="_ _a"></span>oints<span class="_"> </span>and<span class="_ _19"> </span>line</div><div class="t m0 xc h6 y130 ff7 fs4 fc0 sc0 ls0 ws0">segmen<span class="_ _1"></span>ts<span class="_"> </span>are<span class="_"> </span>trac<span class="_ _1"></span>ked<span class="_ _d"> </span>along<span class="_"> </span>a<span class="_"> </span>sequenc<span class="_ _f"></span>e<span class="_"> </span>of<span class="_ _d"> </span>stereo<span class="_"> </span>frames</div><div class="t m0 xc h6 y131 ff7 fs4 fc0 sc0 ls0 ws0">(see<span class="_"> </span>Figure<span class="_"> </span>1),<span class="_"> </span>and<span class="_"> </span>then<span class="_"> </span>the<span class="_"> </span>3D<span class="_"> </span>motion<span class="_ _d"> </span>of<span class="_"> </span>the<span class="_"> </span>camera</div><div class="t m0 xc h6 y132 ff7 fs4 fc0 sc0 ls0 ws0">(and<span class="_ _9"> </span>also<span class="_ _9"> </span>its<span class="_ _9"> </span>uncertaint<span class="_ _1"></span>y)<span class="_ _9"> </span>is<span class="_ _3"> </span>computed<span class="_ _9"> </span>b<span class="_ _1"></span>y<span class="_ _3"> </span>minimizing<span class="_ _9"> </span>the</div><div class="t m0 xc h6 y133 ff7 fs4 fc0 sc0 ls0 ws0">pro<span class="_ _a"></span>jection<span class="_ _9"> </span>errors.</div><div class="t m0 xc h6 y134 ff8 fs4 fc0 sc0 ls0 ws0">A.<span class="_ _19"> </span>Point<span class="_ _9"> </span>F<span class="_ _4"></span>e<span class="_ _1"></span>atur<span class="_ _1"></span>es</div><div class="t m0 xd h6 y135 ff7 fs4 fc0 sc0 ls0 ws0">In<span class="_ _3"> </span>this<span class="_ _6"> </span>work<span class="_ _3"> </span>w<span class="_ _f"></span>e<span class="_ _3"> </span>use<span class="_ _6"> </span>the<span class="_ _6"> </span>w<span class="_ _1"></span>ell-known<span class="_ _3"> </span>ORB<span class="_ _6"> </span>method<span class="_ _6"> </span>[27]</div><div class="t m0 xc h6 y136 ff7 fs4 fc0 sc0 ls0 ws0">due<span class="_ _3"> </span>to<span class="_ _6"> </span>its<span class="_ _3"> </span>great<span class="_ _6"> </span>performance<span class="_ _6"> </span>for<span class="_ _3"> </span>keypoint<span class="_ _3"> </span>detection,<span class="_ _3"> </span>and</div><div class="t m0 xc h6 y137 ff7 fs4 fc0 sc0 ls0 ws0">the<span class="_ _e"> </span>binary<span class="_ _e"> </span>nature<span class="_ _e"> </span>of<span class="_ _b"> </span>the<span class="_ _18"> </span>descriptor<span class="_ _b"> </span>it<span class="_ _18"> </span>provides,<span class="_ _18"> </span>which</div><div class="t m0 xc h6 y138 ff7 fs4 fc0 sc0 ls0 ws0">allo<span class="_ _1"></span>ws<span class="_ _6"> </span>for<span class="_ _9"> </span>a<span class="_ _3"> </span>fast,<span class="_ _3"> </span>e&#64259;cient<span class="_ _3"> </span>k<span class="_ _1"></span>eyp<span class="_ _a"></span>oint<span class="_ _3"> </span>matc<span class="_ _1"></span>hing.<span class="_ _3"> </span>In<span class="_ _6"> </span>order<span class="_ _9"> </span>to</div><div class="t m0 xc h6 y139 ff7 fs4 fc0 sc0 ls0 ws0">reduce<span class="_ _9"> </span>the<span class="_ _9"> </span>num<span class="_ _1"></span>b<span class="_ _a"></span>er<span class="_ _9"> </span>of<span class="_ _3"> </span>outliers,<span class="_ _9"> </span>we<span class="_ _9"> </span>only<span class="_ _9"> </span>consider<span class="_ _9"> </span>measure-</div><div class="t m0 xc h6 y13a ff7 fs4 fc0 sc0 ls0 ws0">men<span class="_ _1"></span>ts<span class="_ _6"> </span>whic<span class="_ _1"></span>h<span class="_ _3"> </span>ful&#64257;ll<span class="_ _3"> </span>that<span class="_ _6"> </span>the<span class="_ _9"> </span>b<span class="_ _a"></span>est<span class="_ _6"> </span>matc<span class="_ _1"></span>h<span class="_ _3"> </span>in<span class="_ _3"> </span>the<span class="_ _6"> </span>left<span class="_ _9"> </span>image</div><div class="t m0 xc h6 y13b ff7 fs4 fc0 sc0 ls0 ws0">corresp<span class="_ _a"></span>onds<span class="_ _3"> </span>to<span class="_ _6"> </span>the<span class="_ _3"> </span>best<span class="_ _6"> </span>matc<span class="_ _1"></span>h<span class="_ _6"> </span>in<span class="_ _3"> </span>the<span class="_ _3"> </span>right<span class="_ _3"> </span>one,<span class="_ _3"> </span>i.e.<span class="_ _3"> </span>they</div><div class="t m0 xc h6 y13c ff7 fs4 fc0 sc0 ls0 ws0">are<span class="_ _9"> </span>mutual<span class="_ _9"> </span>best<span class="_ _3"> </span>matches.<span class="_ _9"> </span>Finally<span class="_ _4"></span>,<span class="_ _9"> </span>we<span class="_ _9"> </span>also<span class="_ _9"> </span>&#64257;lter<span class="_ _9"> </span>out<span class="_ _3"> </span>those</div><div class="t m0 xc h6 y13d ff7 fs4 fc0 sc0 ls0 ws0">matc<span class="_ _1"></span>hes<span class="_ _6"> </span>whose<span class="_ _3"> </span>distance<span class="_ _6"> </span>in<span class="_ _3"> </span>the<span class="_ _6"> </span>descriptor<span class="_ _3"> </span>space<span class="_ _6"> </span>with<span class="_ _3"> </span>the</div><div class="t m0 xc h6 y13e ff7 fs4 fc0 sc0 ls0 ws0">second<span class="_"> </span>best<span class="_"> </span>match<span class="_"> </span>is<span class="_"> </span>less<span class="_"> </span>than<span class="_"> </span>t<span class="_ _1"></span>wice<span class="_"> </span>the<span class="_"> </span>distance<span class="_"> </span>with</div><div class="t m0 xc h6 y13f ff7 fs4 fc0 sc0 ls0 ws0">the<span class="_ _d"> </span>b<span class="_ _a"></span>est<span class="_"> </span>matc<span class="_ _1"></span>h,<span class="_"> </span>to<span class="_ _6"> </span>ensure<span class="_"> </span>that<span class="_ _6"> </span>the<span class="_"> </span>correspondences<span class="_"> </span>are</div><div class="t m0 xc h6 y140 ff7 fs4 fc0 sc0 ls0 ws0">meaningful<span class="_ _9"> </span>enough.</div><div class="t m0 xc h6 y141 ff8 fs4 fc0 sc0 ls0 ws0">B.<span class="_ _19"> </span>Line<span class="_ _9"> </span>Se<span class="_ _1"></span>gment<span class="_ _9"> </span>F<span class="_ _4"></span>e<span class="_ _1"></span>atur<span class="_ _1"></span>es</div><div class="t m0 xd h6 yd5 ff7 fs4 fc0 sc0 ls0 ws0">The<span class="_ _10"> </span>Line<span class="_ _7"> </span>Segment<span class="_ _10"> </span>Detector<span class="_ _7"> </span>(LSD)<span class="_ _10"> </span>metho<span class="_ _2"></span>d<span class="_ _10"> </span>[37]<span class="_ _7"> </span>has<span class="_ _7"> </span>b<span class="_ _a"></span>een</div><div class="t m0 xc h6 yd6 ff7 fs4 fc0 sc0 ls0 ws0">emplo<span class="_ _1"></span>yed<span class="_ _6"> </span>to<span class="_ _3"> </span>extract<span class="_ _6"> </span>line<span class="_ _6"> </span>segmen<span class="_ _1"></span>ts,<span class="_ _6"> </span>providing<span class="_ _3"> </span>high<span class="_ _6"> </span>preci-</div><div class="t m0 xc h6 yd7 ff7 fs4 fc0 sc0 ls0 ws0">sion<span class="_ _9"> </span>and<span class="_ _9"> </span>repeatability<span class="_ _4"></span>.<span class="_ _9"> </span>F<span class="_ _4"></span>or<span class="_ _9"> </span>stereo<span class="_ _9"> </span>matc<span class="_ _1"></span>hing<span class="_ _9"> </span>and<span class="_ _9"> </span>frame-to-</div><div class="t m0 xc h6 yd8 ff7 fs4 fc0 sc0 ls0 ws0">frame<span class="_ _6"> </span>tracking<span class="_ _6"> </span>w<span class="_ _1"></span>e<span class="_ _d"> </span>augment<span class="_ _6"> </span>line<span class="_ _6"> </span>segments<span class="_ _6"> </span>with<span class="_ _6"> </span>a<span class="_ _6"> </span>binary</div><div class="t m0 xc h6 y142 ff7 fs4 fc0 sc0 ls0 ws0">descriptor<span class="_ _6"> </span>pro<span class="_ _1"></span>vided<span class="_ _6"> </span>by<span class="_ _6"> </span>the<span class="_ _3"> </span>Line<span class="_ _6"> </span>Band<span class="_ _6"> </span>Descriptor<span class="_ _6"> </span>(LBD)</div><div class="t m0 xc h6 y8b ff7 fs4 fc0 sc0 ls0 ws0">metho<span class="_ _a"></span>d<span class="_ _b"> </span>[43],<span class="_ _0"> </span>whic<span class="_ _f"></span>h<span class="_ _b"> </span>allows<span class="_ _b"> </span>us<span class="_ _0"> </span>to<span class="_ _b"> </span>&#64257;nd<span class="_ _0"> </span>correspondences</div><div class="t m0 xc h6 y8c ff7 fs4 fc0 sc0 ls0 ws0">b<span class="_ _a"></span>et<span class="_ _f"></span>w<span class="_ _1"></span>een<span class="_ _8"> </span>lines<span class="_ _10"> </span>based<span class="_ _7"> </span>on<span class="_ _7"> </span>their<span class="_ _7"> </span>lo<span class="_ _a"></span>cal<span class="_ _7"> </span>app<span class="_ _a"></span>earance.<span class="_ _7"> </span>Similarly<span class="_ _7"> </span>to</div><div class="t m0 xc h6 y8d ff7 fs4 fc0 sc0 ls0 ws0">the<span class="_ _9"> </span>case<span class="_ _9"> </span>of<span class="_ _3"> </span>points,<span class="_ _9"> </span>we<span class="_ _9"> </span>c<span class="_ _1"></span>heck<span class="_ _9"> </span>that<span class="_ _9"> </span>b<span class="_ _a"></span>oth<span class="_ _9"> </span>candidate<span class="_ _9"> </span>features</div><div class="t m0 xc h6 y32 ff7 fs4 fc0 sc0 ls0 ws0">are<span class="_ _18"> </span>mutual<span class="_ _18"> </span>b<span class="_ _a"></span>est<span class="_ _18"> </span>matches,<span class="_ _18"> </span>and<span class="_ _e"> </span>also<span class="_ _18"> </span>that<span class="_ _e"> </span>the<span class="_ _18"> </span>feature<span class="_ _e"> </span>is</div><div class="t m0 xc h6 y56 ff7 fs4 fc0 sc0 ls0 ws0">meaningful<span class="_ _b"> </span>enough.<span class="_ _b"> </span>Finally<span class="_ _4"></span>,<span class="_ _b"> </span>w<span class="_ _1"></span>e<span class="_ _b"> </span>take<span class="_ _b"> </span>adv<span class="_ _4"></span>antage<span class="_ _b"> </span>of<span class="_ _b"> </span>the</div><div class="t m0 xc h6 y57 ff7 fs4 fc0 sc0 ls0 ws0">useful<span class="_ _9"> </span>geometrical<span class="_ _8"> </span>information<span class="_ _9"> </span>that<span class="_ _9"> </span>line<span class="_ _8"> </span>segments<span class="_ _8"> </span>provide</div><div class="t m0 xc h6 y36 ff7 fs4 fc0 sc0 ls0 ws0">in<span class="_ _19"> </span>order<span class="_ _18"> </span>to<span class="_ _18"> </span>&#64257;lter<span class="_ _18"> </span>out<span class="_ _19"> </span>those<span class="_ _18"> </span>line<span class="_ _18"> </span>matches<span class="_"> </span>with<span class="_ _18"> </span>di&#64256;erent</div><div class="t m0 xc h6 y59 ff7 fs4 fc0 sc0 ls0 ws0">orien<span class="_ _1"></span>tations<span class="_ _9"> </span>and<span class="_ _9"> </span>lengths,<span class="_ _8"> </span>and<span class="_ _9"> </span>those<span class="_ _8"> </span>with<span class="_ _9"> </span>a<span class="_ _8"> </span>high<span class="_ _9"> </span>di&#64256;erence</div><div class="t m0 xc h6 y5a ff7 fs4 fc0 sc0 ls0 ws0">on<span class="_ _3"> </span>the<span class="_ _6"> </span>disparities<span class="_ _3"> </span>of<span class="_ _6"> </span>the<span class="_ _6"> </span>endpoint.<span class="_ _3"> </span>Notice<span class="_ _6"> </span>that<span class="_ _3"> </span>this<span class="_ _6"> </span>&#64257;lter</div><div class="t m0 xc h6 y3a ff7 fs4 fc0 sc0 ls0 ws0">helps<span class="_ _6"> </span>the<span class="_ _3"> </span>system<span class="_ _6"> </span>to<span class="_ _6"> </span>retain<span class="_ _3"> </span>a<span class="_ _6"> </span>larger<span class="_ _6"> </span>amoun<span class="_ _1"></span>t<span class="_ _6"> </span>of<span class="_ _6"> </span>structural</div><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a></div><div class="pi" data-data='{"ctm":[1.568627,0.000000,0.000000,1.568627,0.000000,0.000000]}'></div></div>
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