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how to find or know the values for Z-axis in octomap?

asked 2012-09-12 22:24:59 -0500

Sudhan gravatar image

updated 2012-09-16 23:46:00 -0500

I have an octomap and trying to do localization with it. I trying to make a slice from a 3d-map (octomap) to consider a single 2d plane for localization with amcl package. I uploaded the map in rviz using octomap_server_node,

$ rosrun octomap_server octomap_server_node _occupacy_min_z:=-0.01 _occupancy_max_z:=0.01

I tried different z values in different maps, though I cannot find how the z-values are distributed in the z-axis. I would like to find where the zero of the z-axis lies and I believe that z-values are in meter.

Bottom line is how to slice the 3d map to get a single 2d plane.

Thanks in advance for your suggestions.


The resolution=0.025, so i started bigger values. I use rviz to visualize the map, after using the above command. Either I use values in negative z-plane (ex. {-0.05,0} or positive z-plane {0,0.05}, always the map lies in negative plane of the z-axis (which is viewed in 'rviz'). Also, it seems to be more thicker in z-axis for thickness 0.05m.

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answered 2012-09-13 01:09:46 -0500

AHornung gravatar image

Zero lies in z=0.0m in your global map frame, however you arrange that with tf. That depends on where and how you built your map. Of course all units are meters as it is the standard in ROS.

When you slice with occupancy_min/max_z, make sure that the interval is large enough to hold one voxel, i.e., larger than the octree file resolution.

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i cannot type bigger sentences here. So, please refer the updated part in the question.

Sudhan gravatar image Sudhan  ( 2012-09-14 02:09:44 -0500 )edit

Sorry, but I don't see a real question in the update, or understand what you're trying to achieve...

AHornung gravatar image AHornung  ( 2012-09-14 02:30:32 -0500 )edit

I am trying to take single plane out of the 3d octomap. So, I try to access the values in z-axis of the octomap. But, when I try to acheive it via 'occupancy_min/max_z' parameters, I face the problem described in the updated part. So, I would like know how to access those values. ex. z{0,0.05}.

Sudhan gravatar image Sudhan  ( 2012-09-14 02:58:13 -0500 )edit

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Asked: 2012-09-12 22:24:59 -0500

Seen: 791 times

Last updated: Sep 16 '12