How can I get extrinsic camera parameters from the ROS camera_calibration package

Question

I want to get more a more accurate point cloud and uv-mapping for the Softkinetic Depthsense by calibrating the intrinsic and extrinsic parameters of the depthsense using the ROS camera_calibration package.

The output matrices of the camera_calibration package are:

1. Distortion parameters (D)
2. Intrinsic camera matrix (K)
3. Rectification matrix (R)
4. Projection matrix of the processed (rectified) image (P)

The Depthsense SDK has the option to set the camera parameters in the StereoCameraParameters struct.

How do I get the camera pose (extrinsic parameters) from the camera_calibration output (D, K, R and P)?

The projection matrix (P) contains is the projection onto the rectified image. Decomposing this matrix into a translation and rotation would give the extrinsic parameters of the virtual, rectified camera. What I need to set in the Depthsense SDK are the real camera extrinsics.

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Originally posted by Ronald on ROS Answers with karma: 103 on 2015-03-06

Post score: 1

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Original comments

Comment by Introcert on 2017-08-07:
Hi , I wonder if you have solved this question. I also have the question about how to get the camera extrinsics . And I am desired to get your help. Thanks a lot!

Answer 1

I don't know if I'm answering correctly.

So in this pkg: https://github.com/warp1337/opencv_cam_calibration

You can calibrate your camera, just follow the instructions. Camera calibration .xml file will be next to the executable when you finish. Open the .xml file and you will be able to see your camera Extrinsic parameters matrix.

I may be completely wrong, sorry.

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Originally posted by End-Effector with karma: 162 on 2015-03-10

This answer was ACCEPTED on the original site

Post score: 0

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Original comments

Comment by Ronald on 2015-03-10:
Thank you for your answer. This may indeed be an option to get the extrinsic parameters as well. However, I think that the ros calibration_package also contains the extrinsic camera parameters. I just don't know how to get the extrinsic camera parameters from these four matrices (D, K, R and P).

Comment by Ronald on 2015-03-10:
Even after reading this: http://wiki.ros.org/image_pipeline/CameraInfo I still don't see an option to get the camera extrinsics.

Comment by Jägermeister on 2019-02-22:
You can't get extrinsic parameters with this method.