ar_track_alvar questions

asked 2015-05-08 06:42:22 -0600

Sudarshan gravatar image

updated 2015-05-14 06:21:50 -0600


I am using ar_track_alvar in ROS Hydro (and Groovy) on Ubuntu 12.04. I have a couple of questions about the package.

  1. As I understand and have verified, when using the bundle version, ar_track_alvar provides the pose estimate of the master tag regardless of which tag is visible to the camera. This is definitely helpful, but I was wondering if it would be possible to get the pose estimates of the other tags as well. Consider for example a rectangular box which has two tags on each side (top of the side and bottom of the side) and a tag at the top for a total of 9 tags. If I make the top tag as the master tag, I would like to get the pose estimates of say one of the tags on one of the sides. Is this possible?
  2. Although I am able to detect the tags, when I print the ID and the confidence, I get the confidence value to be always zero. The reason I need the confidence is so that could set a confidence threshold and reject those detected tags which have a lower confidence value than the threshold. But this can't be done if the confidence value is always zero. My approach is to do the checking in the code I write. However, is there any parameters (args) that I can set in the launch file for a confidence threshold? If not, am doing something wrong for the confidence to printed always zero?
  3. The marker tf names that I can see after running view_frames are ar_maker_0, ar_marker_1 etc. Is it possible to customize these names so that they represent the box that is being tagged? For example, if I had a bundle called cherios, then I would like name on the tf tree to by /cherios. How would I do this?

Any help is appreciated,


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Have you found an answer to (2)? I am trying to use the confidence value as well...

I think the answer to (3) might be to create your own fork of the source code...

quantumflux gravatar image quantumflux  ( 2015-08-20 04:16:58 -0600 )edit

Actually, I've been away from my lab on an internship for the summer. I will start working on this next week. But maybe we could connect and try to solve this issue together.

Sudarshan gravatar image Sudarshan  ( 2015-08-20 10:14:35 -0600 )edit

Hi guys, I'm looking to use the confidence value as well, did you manage to solve this issue?

Tanmay gravatar image Tanmay  ( 2015-10-10 07:16:59 -0600 )edit

Nope. I kind of gave up and switched back to ar_pose.

Sudarshan gravatar image Sudarshan  ( 2015-10-10 07:47:23 -0600 )edit

Hi Sudarshan,

Are you working on Indigo? I've used ar_pose before on Hydro, but am facing issues setting it up for Indigo.

Tanmay gravatar image Tanmay  ( 2015-10-11 08:36:27 -0600 )edit

No. My client machine is on Hydro and ROS master is running on Groovy (its a pain to upgrade the computers on our robot, so we just stuck with the installed versions). How are you installing ar_pose? If you build it from source it should work on Indigo without a problem.

Sudarshan gravatar image Sudarshan  ( 2015-10-11 08:55:14 -0600 )edit