Comments (10)
Hi, please see equation 7 of the referenced paper, which should describe the equidistant distortion model employed in kalibr. While there is a more complete model including additional tangential distortion reported in that work, kalibr uses the radially symmetric model detailed on in section II.A of the paper. Note that this is consistent with the work of other groups, which can be found here, equation 3-8.
My understanding of ROS from here is that it currently does not support this model.
However, we found it to return lower reprojection errors for a wide range of optics, which again is consistent with findings in this paper.
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@rehderj, can you provide a paper with the equidistant model that you implemented?
To the best of my knowledge you are right; the ROS tools only support pinhole + radtan.
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Thanks for the pointers! I will look them up and possibly come back with any additional questions.
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Sure, feel free to approach us with additional questions. As an addition, the last comment referred to figure 6 in the Richardson paper, which suggests (for these particular optics) a generally lower reprojection errors as well as a significant gain in accuracy in the peripheral parts of the image.
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If you need to undistort images in ROS using a pinhole camera and an equidistant distortion model, the code in the repo below might be useful for you.
https://github.com/schneith/undistorter
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@schneith: this looks indeed very helpful. Thanks for the pointer! I will test this once I have augmented our data with current calibration in CameraInfo format.
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So while implementing the calibration model in our system an additional question came up about the undistort function:
@schneith uses a fixed number of 20 iterations to compute the undistorted radius. Why 20? Is this value just common wisdom for "large enough"? What could be an appropriate abort criteria?
P.S.: The undistorter ROS package works nicely with our calibration values to rectify recorded sequences, thanks @schneith.
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One more question actually about @schneith 's implementation: Is there a reason that there is no check for really small thetad
in undistort
, like there is for r
in distort
.
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There is little justification for the specific number of 20 iterations. Feels free to implement your favorite abort criterion, good candidates might either be the amount of change in the incidence angle theta in subsequent iterations or the absolute difference between the measured distorted theta and your modelled distorted theta when applying the distortion to the current estimate.
The check for small r is for numerical stability. We have not evaluated if it is necessary, nor whether there cannot arise numerical instabilities in the undistortion under all circumstances.
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That makes perfect sense, thank you!
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Related Issues (20)
- Sample rosbag dataset is not working HOT 2
- Some issue about reprojection error and imu error HOT 2
- Error: No module named wx
- An error about running a camera calibration HOT 3
- The Calibration Targets in the Wiki are all missing. HOT 3
- My calibrated translation vector is not quite right caused by incorrect scaling of accelerometer measurements HOT 2
- Influence of IMU sampling interval on the IMU-camera calibration HOT 1
- Calibration tag pdf and config url are not working HOT 2
- Dynamic calibration completed way faster than expected HOT 1
- CHOLMOD warning: matrix not positive definite. file: ../Supernodal/t_cholmod_super_numeric.c line: 911
- camera extrinsic and re projection matrix HOT 2
- Reprojecction Error Range Clarification HOT 2
- Wrong tangential distortion in visualizer
- Visual-inertial calibration on a ground robot HOT 1
- Cannot download the muti-cam ros bag file in https://github.com/ethz-asl/kalibr/wiki/downloads HOT 2
- Why can't I install ros? HOT 1
- bad IMU timestamps HOT 1
- StereoCameras Vins Fusion HOT 1
- How to only build a specific package?
- IsValid() for pinhole camera seems wrong HOT 1
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