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Camera Pose Calibration Valid_Pattern_Ratio_Threshold and Circle Spacing

asked 2017-09-28 09:12:57 -0500

Marco Braun gravatar image

updated 2017-09-28 10:47:53 -0500

gvdhoorn gravatar image

Hi, I started working with the Camera Pose Calibration Package by Delft Robotics ( ) to find extrinsic calibration parameters for a Realsense SR300 camera. I tried to use the calibration service, but I am unsure regarding some service parameters, especially the calibration pattern. After a few hours of debugging I am able to call the calibration service and get the transform matrix, but there are two issues remaining.

  1. Unfortunately the values change significantly from one service call to another, but this could be noise. Maybe I have to adjust the “valid_pattern_ratio_threshold” and the “neighbor_distance”?

  2. I use a 4x11 asymmetric circle grid (""). There is a parameter called “circle spacing” which is 2cm, but I think this isn’t the “patterin_distance” which has to be used.

Thanks for replies!

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answered 2017-09-28 11:00:07 -0500

Ronald gravatar image

The pattern_distance is the distance between two neighbouring circles (be aware to be consistent with units of length throughout your application). You could also try to calibrate without ROS first to see if it works. You can just link to it as a library.

Your pattern widht and height should be fine. This is the number of circles of the pattern in each direction.

You could leave pattern_neighbor_distance to 0, this is just optional to average noise around the detected circle point. (I should indeed clear this up in the documentation and in the code, now that I look at it, it is quite confusing).

You could also check if the point cloud data from the camera is very noisy, since this serves as input to the algorithm.

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Asked: 2017-09-28 09:12:14 -0500

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Last updated: Sep 28 '17