Camera Calibration with driveworks-1.2

Autonomous Vehicles DRIVE PX 2 DriveWorks
1

Hello,

We are trying to calibrate a setup with 4 cameras inside the lab, with the cameras mounted on a provisional structure so that we go through the calibration steps. We still haven’t completed all the steps successfully, so we’ve got a couple of questions:

(1) Is it necessary to have all the vehicle data for the rig file? If we’re not mounting the cameras in the car, should we just set all variables to 0?

(2) Must only two targets be framed in each photo taken for the /external folder? That means, if there are 3 targets in a photo, this is not going to be valid for the calibration process?

(3) What is the key ‘ignore_targets’ in the special-targets.json file? In which case should that be used?

Thank you.

2

Dear Reway,

Please see below update. Thanks.

(1) Is it necessary to have all the vehicle data for the rig file? If we’re not mounting the cameras in the car, should we just set all variables to 0?

If this is only for calibration, then the values wheelBase and wheelDiameter should be kept.

(2) Must only two targets be framed in each photo taken for the /external folder? That means, if there are 3 targets in a photo, this is not going to be valid for the calibration process?

Should be fine with any number of targets in the external photo

(3) What is the key ‘ignore_targets’ in the special-targets.json file? In which case should that be used?

If you have some targets in the scene and you cannot remove them physically, but would like not to contribute to the calibration, then you add them there.

3

Hi Steve,

Thanks for your reply.

The thing is that we are getting a huge projection error (e+08) for the intrinsics of the camera external. Please see below update.

Initializing camera intrinsics
Initializing intrinsics for camera external
OcamCalib: initial calib
Closed form result: 2304,1728,656.009,0,-0.000284028,3.71037e-07,-9.8216e-11, error: 4.1572e+08

Before camera: intrinsics=        2304         1728      0.56703            0            0       251.35            0 -0.000103839  6.00711e-09 -7.81882e-13      1616.65     -5355.57      9482.81     -4513.18     -18864.8      39934.6     -23977.9     -3669.91      4873.26
After  camera: intrinsics=        2304         1728     0.326809            0            0      151.476     0.102006 -0.000109626   1.0279e-08 -7.43281e-13         1945     -8455.41        16299     -7185.19     -24259.2      39741.2     -19301.6     -674.444      2014.77
Error after: Median=358.25, mean=2170.16, var=2.91703e+08, std dev=17079.3, sample count=4484, min=0.0170339, max=507671
Max fov: 241.202

We placed one target in front of each ar0231 camera, two targets on the floor and took several images from the setup with this external camera (with fixed focal length). The targets were printed in DIN A0 and have their size adjusted to this size.

Any idea on what could be causing that?

Thanks.

4

Dear Reway,

Could you let us know your calibration step in detail? Thanks.