Purpose

Exwayz Loop Closure aims at compensating for the drift of an odometry trajectory or a coarsly georeferenced trajectory.

It detects similar areas that were scanned multiple times in the dataset (called loops, even if the trajectory doesn’t loop strictly speaking)
It computes a loop closure observation
Then it optimizes the full trajectory taking into account all the loop closure observations computed by the software.

<aside> 💡 Check the 4. Close the loops tutorial to learn easily how to run the loop closure.

</aside>

Command line options

Name	Command line prefix	Default value	Definition
Frames	`-i`	Required	Path to directory containing frames of the SLAM session
Trajectory	`-t`	Required	Path to the support trajectory used to guess “loops”. Check 4. Close the loops if needed.
Profile	`-p`	Odometry	Loop closure profile used by the software. This profile contains processing parameters, that shoudl be adjust depending on the used support trajectory. When using an odometry support trajectory, it is recommended to use the Odometry profile. When a pre-georeferencing step has been performed, we recommend to use the GPS profile.
Distance between loops	`-d`	5.0	This parameter prevents the software from searching for new loops at each new frame index. It will force the algorithm to search loops on trajectory points spaced by `-d` meters.
Output path	`-o`	./traj_loop_closure.ply	Output path for optimized trajectory.

Output

`traj_loop_closure.ply`	Optimized trajectory with loop closure corrections.
`lc_observations.yamlc`	Loop closure observations computed by the software. These measures can be input to `exwayz_georef` .