What is a cluster in RTAB-Map?

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These parameters are used for the occupancy grid.

rtabmap --params | grep Cluster
Param: Grid/ClusterRadius = "0.1"   [[Grid/NormalsSegmentation=true] Cluster maximum radius.]
Param: Grid/MinClusterSize = "10"   [[Grid/NormalsSegmentation=true] Minimum cluster size to project the points.]

They are used when Grid/NormalsSegmentation=true:

rtabmap --params | grep Grid/NormalsSegmentation
Param: Grid/NormalsSegmentation = "true" [Segment ground from obstacles using point normals, otherwise a fast passthrough is used.]

Then to know more about this approach, look at the code here: https://github.com/introlab/rtabmap/b...

So specifically for your question, the cluster parameters are used to cluster the point clouds into multiple surfaces. This can also filter some noise.

Some examples of results:

• http://wiki.ros.org/rtabmap_ros#rtabm...

• http://wiki.ros.org/rtabmap_ros/Tutor...

• http://official-rtab-map-forum.206.s1...

• https://github.com/introlab/rtabmap_r...

• "RTAB-Map as an open-source lidar and visual simultaneous localization and mapping library for large-scale and long-term online operation" https://introlab.3it.usherbrooke.ca/m... (fig. 14 d, i)