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TF Frame Convention for Stereo Cameras

asked 2011-04-26 20:19:15 -0500

mkoval gravatar image

updated 2011-06-17 11:17:57 -0500

mmwise gravatar image

I am using a stereo camera for both stereo reconstruction and monocular image processing. Since I am not calibrating the pair of cameras twice, I am doing all of the monocular processing using the stereo calibration parameters. For the camera intrinsics, this works fine. I am not sure how to handle the extrinsics.

I would like to have the left and right cameras in different TF frames that correspond to their positions on my robot (e.g. /stereo_left_link and /stereo_right_link). Since the stereo baseline is encoded in the stereo calibration parameters, I am not sure stereo_image_proc will deal with the two images being in different TF frames.

What is the correct way to set the CameraInfo and Image message frame_ids to safely proceed to avoid being affected by the potential inconsistencies?

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answered 2011-06-30 05:53:02 -0500

tfoote gravatar image

You could check out uvc_camera's stereo_node as somewhere to start.

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answered 2011-06-17 11:01:43 -0500

mmwise gravatar image

typically each camera in a stereo pair is assigned a different tf frame and the camera info for each camera contains the frame information

# Time of image acquisition, camera coordinate frame ID
Header header    # Header timestamp should be acquisition time of image
                 # Header frame_id should be optical frame of camera
                 # origin of frame should be optical center of camera
                 # +x should point to the right in the image
                 # +y should point down in the image
                 # +z should point into the plane of the image

stereo_image_proc listens on the right/camera_info and left/camera_info topics

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I believe I have already tried this, but stereo_image_proc complains that the left and right TF frames do not match.
mkoval gravatar image mkoval  ( 2011-06-17 18:31:40 -0500 )edit
if you look at this question http://answers.ros.org/question/106/how-to-add-kinect-sensor-input-to-a-urdf-model#175 this is how we model the kinect for the turtlebot
mmwise gravatar image mmwise  ( 2011-06-18 09:07:37 -0500 )edit
Thanks for the link, but it is solving a different problem. I would like left/{image,camera_info} to have TF frame /stereo_left_link and right/{image,camera_info} to have TF frame /stereo_right_link. However, this triggers an assertion that left.frame != right.frame.
mkoval gravatar image mkoval  ( 2011-06-27 03:50:16 -0500 )edit
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answered 2011-06-26 23:04:57 -0500

rajat gravatar image

Are you able to slove the problem, i am having the same problem , whenever i use stereo_image_proc , stereo vslam crashes saying that , assertion of right_.tf=left_tf failed .

Do you have any idea how to solve this problem?

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I still haven't figured out how to get stereo_image_proc working without putting both cameras in the same TF frame.
mkoval gravatar image mkoval  ( 2011-06-27 03:46:47 -0500 )edit
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answered 2011-06-27 23:57:41 -0500

rajat gravatar image

can you tell me how to put both the cameras in same TF frame .???

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Asked: 2011-04-26 20:19:15 -0500

Seen: 2,183 times

Last updated: Jun 30 '11