This dissertation provides a unique use for airborne laser scanning sensors. In effect it replaces the GPS updates to the IMU with a dead reckoning terrain navigation system based on the laser scanner data. For those situations when GPS is not available this approach can be an important replacement and/or backup system.
By using two laser scanning sensors, one looking forward and the other nadir the IMU drift can be estimated from the differences in location of the same point on the ground. There are obvious issues with the cost of such a system as well as its all weather limitations, but this may be an important new area of research for airborne laser scanner technology.
This area is very active in autonomous vehicle navigation using profile lidars to detect static features, which can then be used to aid an IMU based on displacement errors. Looks to be a good dissertation