The resynchronization is an option for letting the exwayz_georef.exe trying to resynchronize the input GNSS trajectory and odometry trajectories.

<aside> ⚠️ It is always better to have a hardware synchronization between the LiDAR and the GNSS that using the resynchronization option. If the two trajectories have a known time offset, prefer using the --odometry-time-offset option if exwayz_georef.exe instead of the -r option

</aside>

The principle is to match the velocity profiles of each trajectory in order to find the time offset between the two.

<aside> 💡 As the GNSS measures don’t contain a velocity field, it is estimated using finite differences.

</aside>

As an example, below are in red is the velocity profile of an odometry trajectory and in green the velocity profile of the associated GNSS trajectory.

The resynchronization tries to match these profiles as best as possible, this naturally gives the time offset between the trajectories if the operation succeeds

Failure cases

The resynchronization naturally fails if

• the trajectory are constant velocity
• the positions are too noisy on the GNSS (no RTK for instance could lead to this situation)