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Accuracy of AR markers tracking without depth data improvements?

asked 2014-03-06 21:34:52 -0500

bwillaert gravatar image

Hi,

I have been using the individualMarkers node from the ar_track_alvar package successfully. With the individualMarkersNoKinect however, the detected markers are about 5 cm 'below' the right location. Apparently this depth data based improvement is important: if I comment out the

int ret = PlaneFitPoseImprovement(i, m->ros_corners_3D, selected_points, cloud, m->pose);

line in the individualMarkers code, I get a similarly large error.

Is that really the best accuracy you can get without using the depth data?

I am using a close range primesense camera with markers not more than 1 meter away from the camera. The marker size is 7 cm. When using the individualMarkersNoKinect node, I use the following topics: /camera/rgb/image_raw
/camera/rgb/camera_info

Thanks for any feedback,

Bert

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In the meantime, I did a calibration of the rgd camera (using http://wiki.ros.org/camera_calibration) and that improved the 2d based tracking accuracy. The errors are now < 2 cm in the direction from the camera to the marker location. Depending on the camera quality and the calibration quality, I assume now that's the best possible...

bwillaert gravatar image bwillaert  ( 2014-03-11 06:44:13 -0500 )edit

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answered 2014-04-30 16:34:11 -0500

sniekum gravatar image

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.

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Is the assumption correct, that one is supposed to measure the outside edges (e.g. furthest left black edge to furthest right black edge)?

bit-pirate gravatar image bit-pirate  ( 2015-12-08 02:27:03 -0500 )edit

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Asked: 2014-03-06 21:34:52 -0500

Seen: 1,315 times

Last updated: Apr 30 '14