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localizing multiple ARMarkers using ar_pose

asked 2012-02-27 19:01:33 -0500

ben gravatar image

updated 2014-01-28 17:11:30 -0500

ngrennan gravatar image

I have some general questions about ARMarkers and also the ROS wrapper, ar_pose. I searched for general information on using them in practice but couldn't find any detailed information.

  1. What is the maximum number of ARMarkers that can be used in a scene at once? I'm assuming it depends on the dimensions of the markers...
  2. What's the expected amount of error when localizing a marker from 5ft away?
  3. What's the smallest size marker that a camera can localize 'accurately' from 5ft away? (Is there such a thing as 4cm x 4cm markers? Do they get smaller than that?)
  4. How much does the accuracy improve when going from a 640x480 camera to a 2MP camera?
  5. What is the average frame rate from the ar_pose node that is capable of detecting multiple armarkers? When using a 640x480 camera and a 2MP camera?

My goal is to put markers on 25 dishes or so on a tabletop and some shelves. The camera won't ever be more than 6ft away. Is that doable?

Any tips or lessons learned from experience would be appreciated.

Thank you very much in advance!

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answered 2012-02-29 09:57:53 -0500

Procópio gravatar image

Hi. I have been using ar_pose for some time, but I am afraid I cannot answer exactly your questions, but maybe give some insights.

  1. I think there is no limit (but I may be wrong).
  2. Do not know, never measured it.
  3. It depends on your camera resolution and its distance to the markers, you can make your markers very small as long as your camera can see their details.
  4. Same as 2.
  5. That depends on your computer power and the number of markers you are detecting.

I am using markers as an easy way to track people. I created big hats (markers are 25x25 cm) and the markers can get very far, and still be detected. My ar_pose frame rate is pretty much limited by the camera frame rate. I think your goal is doable, you just need to find a proper configuration of markers size/camera resolution/camera distance.

Hope this helps.

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Asked: 2012-02-27 19:01:33 -0500

Seen: 415 times

Last updated: Feb 29 '12