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Multi-tag bundles detection of ar_track_alvar

asked 2013-04-10 08:21:14 -0600

zieben gravatar image

updated 2013-04-10 09:33:55 -0600

I have some problem to detect Multi-tag bundles through ar_track_alvar. According to the wiki,

To create a bundle, first choose which tag you want to be the master tag. Treat the center of the master tag as (0,0,0). Then, after placing the rest of the tags, measure the x, y, and z coordinate for each of the 4 corners of all of the tags, relative to the master tag origin. Enter these measurements for each tag into the XML file starting with the lower left corner and prograssing clockwise around the tag.

So I think I should add points in XML file as this sequences: lower left -> upper left -> upper right -> lower right.

However, an example XML file included in ar_track_alvar seems like not to follow that rules. (It progresses counter-clockiwise around tag. e.g. lower left -> lower right -> upper right -> upper left)

I also tried to make XML file through createMarker. However, it is also weird. 4 points generated by it are center -> lower right -> upper right -> upper left.

I tried three of them. When I check it through rviz, all three cases cannot detect master tag (red square marker appears different position and orientation) However, other markers except for master one are well detected as green marker.

So what was my fault or what I have to do more?

Thank you.

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answered 2013-04-11 21:58:47 -0600

jacky_90 gravatar image

Yes, you have to consider the corners counter-clockwise. But I have never used createMarker.

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Asked: 2013-04-10 08:21:14 -0600

Seen: 669 times

Last updated: Apr 11 '13