The angle of the tracking camera mount on m500

yu zhang

Hi team,
I am wondering what is the angle of the tracking camera mount on m500?
https://www.modalai.com/products/tracking-image-sensor-mount

I roughly measured it for a 35 degree, and I am not sure if there is an error.

Also, I am wondering why it is designed for such a specific angle downward? Is it required by the VIO algorithm? Or is it a tested result for a better VIO tracking performance? What if changing the angle, will the VIO be impacted?

Thanks.

The angle is 45 degrees, this was to give VIO a good view of the ground while also not being completely obscured when landed. You can freely change the angle/position of the camera but you will need to update /etc/modalai/extrinsics.conf appropriately

yu zhang

@Alex-Gardner Thanks so much for the information! And I will have a look at the configuration file.

yu zhang

Hi @Alex-Gardner, I also have a couple of questions about the calibration after changing those configuration files.

For example, if I would change the angle in /etc/modalai/extrinsics.conf, I should have to calibrate the camera after this, right?

This link shows a process of using voxl-calibrate-camera to calibrate ethier tracking camera or stereo. https://docs.modalai.com/calibrate-cameras/

Since it uses a printed black/white grid paper in the calibration, I am wondering do you have a copy of this grid to download and print as a standard tool?

Also, I noticed VOXL uses 1kHz IMU as default sampling rate, what if I would change the IMU's rate, should I have to calibrate it following this link https://docs.modalai.com/calibrate-imu/ too, right?

And I am wondering if changing the IMU's rate could impact the fusion process for VIO? Or simply make a IMU calibration after that is all right to VIO?

The intrinsics of the camera won't change when you move the camera, so you wouldn't have to recalibrate the tracking camera if you move it, and you would only have to recalibrate the stereo extrinsics if you moved those.

The imu won't require a recalibration if you change the sample rate.

Changing the sample rate may impact VIO performance if you change it a significant amount, but you won't need to change any configuration for VIO.

yu zhang

@Alex-Gardner All right, thanks so much for double-checking