sniekum's profile - activity

This seems odd. If the position of the tag is being estimated as "behind" where the tag really is, it usually means that the measurement of the size of tag is incorrect, leading it to think it is a different distance away. The measurement should be done from side to side (not corner to corner) of the black edges of the tag.

I'm not sure how you are going about making your own AR tags, but the only supported way to make AR tags with ar_track_alvar is the included executable that produces them from given parameters. AR tags are not a single monolithic standard, so I'm assuming you are trying to use some protocol that you've seen with other types of AR tags to encode the information. ar_track_alvar only supports encoded ID numbers and those are produced through the included executable.

If you are willing to modify the ar_track_alvar code, pixel location is actually calculated before 3D position, so you could publish that to a topic. However, it might be significantly easier just to project the x,y,z coordinates back onto the image plane. That's essentially what rviz is doing anyway, so that it can visualize the AR tags.

We've switched groovy development to Github, but haven't updated the doc page, sorry. Check out the latest version and switch to the groovy-devel branch (although I'm pretty sure that is the default branch right now):

git clone https://github.com/sniekum/ar_track_alvar.git git checkout groovy-devel

AnSooooo, it looks like you are trying to have it publish the markers poses in the /torso_lift_link frame, which may not exist if you aren't working on a PR2. Try publishing in a different frame.