Zed-ros-wrapper: the calibration between the imu and cameras using kalibr

[chenwinki]

Dear author: :+1:
I using kalibr calibrate zed mini, I tried 20 times, But the timeoffset between imu and cameras is about 0.2 second, it is too large with imu: 800hz and camera:15hz, could you give me a hint? or the code of driver has a bug?

[Myzhar]

We are going to check it.

Can you provide us with your configuration files and with a link to the procedure you followed? In this way we can try better to replicate the problem

[chenwinki]

This is the calibration procedure kalibr https://github.com/ethz-asl/kalibr ,I use this to calibrate stereo cameras, and imu between stereo cameras.The target used for kalibr
target.txt

And I use imu_utils to calibrate imu to get the noise and bias , I got the result
imu_param.txt

and the calibration result
results-imucam-camimu800_2018-11-25-14-45-53.txt

[chenwinki]

@Myzhar hello, could you give me some hint about how do you calibrate camera and imu, and the result.
You should have got accurate result, because people use zed sdk without providing the parameters.

[Myzhar]

We are working on a tutorial on using Kalibr. Stay tuned ;)

[chenwinki]

Waiting for your message！

[Myzhar]

Here you are:
https://support.stereolabs.com/hc/en-us/articles/360012749113-How-can-I-use-Kalibr-with-the-ZED-Mini-camera-in-ROS-

[chenwinki]

@Myzhar Thank you for your work!
1、but the timeoffset is still around 0.1s, this means the IMU and cameras is not synchronized in the zed-ros-wrapper? when I use the imu and camera ,I should consider the timeoffset.
2、when I set the parameter imu_timestamp_sync in the file zed_camera.launch to true, this means the timestamp of some imu msgs will be same?
hope for your reply!

[Myzhar]

@chenwinki

1. The IMU is faster than the camera, so a timeoffset is expected. The less the camera framerate, the more is the timeoffset. Furthermore you must think about USB buffering and other OS factors.
2. Exactly. An example: IMU 800Hz, camera 30 FPS. If you enable sync you will get at least 26 IMU messages with the same timestamp that is the timestamp of the latest grabbed image.