[hellllllllooo]

It's using ICP to register sucessive lidar scans. All three lidars are calibrated so the relative positions are known and the data from all three can be combined.

https://en.m.wikipedia.org/wiki/Iterative_closest_point

This alone isn't SLAM but can be used for odometry as part of a SLAM system.

[jvanderbot]

... which is not surprising they can register in near real time. ICP is not that expensive.