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Hello community!

I've got a question about tracking AR Tags with the "ar_track_alvar" package. I set up the package and subscrided to my kinect image topic. Everything runs fine. The tags, that come with the package (ID 0-20), are detected immediately and I see the corresponding TFs in rviz. So far, so good...

But now I wanted to create my own AR Tags, that carry additional information beyond a number called "ID" (e.g. the name/number of a room) to use them as landmarks. But as it turns out, the ar track alvar node seems to recognize just some of my custom AR tags. Tags that contain real text information like "Room G 301" aren't recognized at all, and even Tags that just contain a pure ID (e.g. "167") are not recognized. But in some cases (e.g. "200"), the ID is recognized.

I tried different sizes, distances, angles.... could not find a pattern. Does anyone know why the ar track alvar is so choosey in what it recognized and what not?

regards psei


Originally posted by psei on ROS Answers with karma: 318 on 2014-02-11

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Original comments

Comment by miloup on 2014-03-30:
Hi, I'm a beginner in ROS that I need it for my project. Is there a tutorial that explains how to 1-connect camera to ROS in order to see the frames captured. 2-Identify the AR Tags

I'm looking for some code examples. I only found one that deals with CUBE/SPHERE...etc. Nothing about codes that detects AR tags.

Thank you

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1 Answer 1

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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.


Originally posted by sniekum with karma: 101 on 2014-02-15

This answer was ACCEPTED on the original site

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Original comments

Comment by hc on 2016-09-08:
Even with the ros node that creates the markers, most of them are not detectable. Say you add a string with the ar tag. It is not able to detect it

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