Timeshift Calculation

[jared.s...@gmail.com]

Hi,

Thanks for all the work you've put into Kalibr! It's helped us tremendously.

I just have a quick question about the timeshift calculation. Specifically, at line 472 of IccSensors.py (https://github.com/ethz-asl/kalibr/blob/master/aslam_offline_calibration/kalibr/python/kalibr_imu_camera_calibration/IccSensors.py#L472), could anyone explain why timeshiftCamToImuPrior is being added to cameraTimeToImuTimeDv.toScalar() to arrive at the post-optimization time offset? I would have thought the post-optimization offset would simply be cameraTimeToImuTimeDv.toScalar().

Thanks in advance,
Jared

[Thomas Schneider]

Hi Jared,

The raw timestamps of all camera observations get shifted by the initial time offset guess so that the timestamps are roughly aligned during the optimization.
see https://github.com/ethz-asl/kalibr/blob/master/aslam_offline_calibration/kalibr/python/kalibr_imu_camera_calibration/IccSensors.py#L243

Consequently this initial offset is added to the offset of the optimization to obtain the total offset.

Best,
Thomas