Difference between /octomap_grid and /grid_map

[mmaissan]

Hello,

I am unsure what the difference is between the octomap_grid and the grid_map occupancy grids. As I understand, both project 3D objects onto a 2D plane. In which situations should I use the one over the other? To me, it seems like they will output the exact same thing, where octomap_grid is based on the OctoMap 3D fused point cloud map.

Thank you and best regards,
Marco

[matlabbe]

Hi,

In most scenarios, they will indeed output the same thing. The local maps are created the same way for both, it is when we assemble them that it may have some variations, in particular for dynamic obstacles. For /grid_map, local grids are projected in 2D and then assembled, overwriting the previous occupied cells in 2D (independently of the height of the obstacles). For OctoMap (/octomap_grid), the are assembled in 3D, then the whole assembled 3D grid is projected in 2D, it may preserve some 3D obstacles that the former approach would have cleared.

cheers,
Mathieu