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hello! I discovered something weird with ar_track_alvar but maybe I just forgot something when launching it. I put a mark on the head of a robot and another one one the ground, this is when it is working fine: OK

but if i make the robot turn a little bit mor to the left, a PI rotation relative to the green axe seems to be made :


I set up a static_transform_publisher between "/axis_camera" and "/map, then I set the "output_frame" argument of ar_track_alvar to "/axis_camera" and the rest of the launchfile is identical to "pr2_indiv_no_kinect.launch".

The problem is not happening with the mark on the ground if i make it turn.

If it can give a clue, here is the rotation data of the mark when my robot make a complete turn: image description

I am grateful for any help!

Originally posted by scarlett on ROS Answers with karma: 170 on 2015-04-27

Post score: 0

Original comments

Comment by scarlett on 2015-05-01:
I am trying to improve camera calibrations, it might solve the problem, I will let you know !


1 Answer 1


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I am not sure about that but could it be that your camera distortion on the edges of the images and the strong skew of the markers in your case cause this misdetection? Try it again with markers facing the camera and see if the problem persists.

Originally posted by Mehdi. with karma: 3339 on 2015-04-28

This answer was ACCEPTED on the original site

Post score: 1


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