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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.

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.

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

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