OS-1 IMU Timestamping

perfo897

I'm trying to find documentation on the OS-1 hardware timestamps, but only see them mentioned in the os1_packet.h header in the ouster_lidar git.

In the header there are three IMU timestamps:
imu_sys_ts, imu_accel_ts, imu_gyro_ts
I was expecting two, one for the accelerometer and one for the gyro.
As the code is not using the timestamps, I wonder where I can find a description on how they are meant to be used?

Best regards
Per-Erik

Mohit

Hi @perfo897
Please see the section 3.5 of Software User Guide
Hope this helps!

perfo897

Thanks,

Apparently the file was renamed, I found it here:
https://data.ouster.io/downloads/OS1-sw-user-guide-v1.12.0.pdf

The description in sec 3.5 gives more details, but It did not clarify the issue I had with the three timestamps though.
In the software guide, they are called ”IMU read time”, ”accelerometer read time”, and ”gyroscope read time”. It also says that ”IMU read time” is monotonic system time since boot”, and that the other two will depend on what timestamping mode is used.

We would like to have IMU timestamps that are as close as possible to the sensor readout, and using the same clock as the Lidar timestamps. Is it sufficient to use the ”accelerometer read time” and the ”gyroscope read time” then? Or should we somehow use the ”IMU read time” to convert between the clocks? I also wonder if the timestamp_mode setting is important also for the internal Lidar-IMU sync, or is it only relevant when external sync is needed?

Cheers
Per-Erik

svc

I am also very interested too the answer to these questions, any luck?