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  • A Partitioned Approach for Efficient

    Graph-Based Place Recognition

    Mattia G. Gollub, Renaud Dubé, Hannes Sommer,

    Igor Gilitschenski, Roland Siegwart

  • Problem

     Processing 3D point clouds can be computationally expensive.

  • Problem

     Processing 3D point clouds can be computationally expensive.

    Idea

    Recognize places on the basis of segment matching.

  • Why segments?

     Good compromise between local and global descriptors.

  • Why segments?

     Good compromise between local and global descriptors.

     Do not rely on the “presence of objects” in the scene.

  • Why segments?

     Good compromise between local and global descriptors.

     Do not rely on the “presence of objects” in the scene.

     Do not rely on a “perfect segmentation”.

  • Why segments?

     Good compromise between local and global descriptors.

     Do not rely on the “presence of objects” in the scene.

     Do not rely on a “perfect segmentation”.

     Allow for descriptive and compact map representation.

  • Ground removal + Euclidean segmentation.

  • Eigen value based features [1].

    [1] Weinmann, M., Jutzi, B., & Mallet, C. (2014). Semantic 3D scene interpretation: a framework combining optimal neighborhood size

    selection with relevant features. ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2(3), 181.

  • (1) k-NN retrieval.

    (2) Random forest classifier trained on separate data.

  • Simple descriptors  High fraction of false correspondences.

    Geometric consistency grouping method [2].

    [2] Chen, H., & Bhanu, B. (2007). 3D free-form object recognition in range images using local surface patches. Pattern Recognition

    Letters, 28(10), 1252-1262.

  • Target map

  • Geometric consistency grouping [2]

  • Geometric consistency grouping [2]

     Find the largest group of pairwise geometrically consistent correspondences.

    [2] Chen, H., & Bhanu, B. (2007). 3D free-form object recognition in range images using local surface patches. Pattern Recognition

    Letters, 28(10), 1252-1262.

  • Geometric consistency grouping [2]

     Find the largest group of pairwise geometrically consistent correspondences.

    Method:

    1. For each correspondence, initialize a new group.

    [2] Chen, H., & Bhanu, B. (2007). 3D free-form object recognition in range images using local surface patches. Pattern Recognition

    Letters, 28(10), 1252-1262.

  • Geometric consistency grouping [2]

     Find the largest group of pairwise geometrically consistent correspondences.

    Method:

    1. For each correspondence, initialize a new group.

    2. For each group, iterate over all the other correspondences. Add the correspondence

    to the group if it is consistent with all the elements in the group.

    [2] Chen, H., & Bhanu, B. (2007). 3D free-form object recognition in range images using local surface patches. Pattern Recognition

    Letters, 28(10), 1252-1262.

  • Geometric consistency grouping [2]

     Find the largest group of pairwise geometrically consistent correspondences.

    Method:

    1. For each correspondence, initialize a new group.

    2. For each group, iterate over all the other correspondences. Add the correspondence

    to the group if it is consistent with all the elements in the group.

    3. Select the biggest group and obtain the localization transformation with RANSAC.

    [2] Chen, H., & Bhanu, B. (2007). 3D free-form object recognition in range images using local surface patches. Pattern Recognition

    Letters, 28(10), 1252-1262.

  • Geometric consistency grouping [2]

     Worst case asymptotic complexity

     Can find a suboptimal solution depending on vertices ordering.

  • Graph-based recognition

     Problem represented as a consistency graph:

     Correspondences  Vertices

     Consistencies  Edges

  • Graph-based recognition

     Problem represented as a consistency graph:

     Correspondences  Vertices

     Consistencies  Edges

     Solved by maximum clique detection.

  • Graph-based recognition

     Problem represented as a consistency graph:

     Correspondences  Vertices

     Consistencies  Edges

     Solved by maximum clique detection.

     Identify transformation by least squares (Umeyama method).

  • Graph-based recognition

     Problem represented as a consistency graph:

     Correspondences  Vertices

     Consistencies  Edges

     Solved by maximum clique detection.

     Identify transformation by least squares (Umeyama method).

    Naïve graph construction

  • Graph-based recognition

     Problem represented as a consistency graph:

     Correspondences  Vertices

     Consistencies  Edges

     Solved by maximum clique detection.

     Generally NP-complete

     Identify transformation by least squares (Umeyama method).

    Naïve graph construction

  • Partition-based graph construction

  • Partition-based graph construction

    Observation: Two consistent correspondences must follow

  • Partition-based graph construction

    Observation: Two consistent correspondences must follow

    Target map

    Local map

  • Partition-based graph construction

  • Maximum clique detection

    We take advantage of the sparseness of the graph.

    [3] Eppstein, D., Löffler, M., & Strash, D. (2010, December). Listing all maximal cliques in sparse graphs in near-optimal time. In

    International Symposium on Algorithms and Computation (pp. 403-414). Springer, Berlin, Heidelberg.

  • Maximum clique detection

    We take advantage of the sparseness of the graph.

    Search for maximum clique as proposed by Eppstein et al. [3].

    [3] Eppstein, D., Löffler, M., & Strash, D. (2010, December). Listing all maximal cliques in sparse graphs in near-optimal time. In

    International Symposium on Algorithms and Computation (pp. 403-414). Springer, Berlin, Heidelberg.

  • Results

  • Results

  • Thank you!

    https://github.com/ethz-asl/segmatch

    IROS SLAM 1 Session MoBT7.2

    [email protected]

    [email protected]

    https://ras.papercept.net/conferences/conferences/IROS17/program/IROS17_ContentListWeb_2.html#mobt7_02