Moving through busy environments is a complex task that is becoming increasingly easy for computer systems to perform on the groud. The task is made even harder while flying if you want to fly low to the ground. New obstacles become serious problems, like power lines and overpasses. A team at Carnegie Mellon University have modified a UAV to fly low to the ground successfully.
The UAV can have a pre-loaded map or it can build its map as it flies using its laser range finder sensors. The lasers sweep an oval pattern out front of the vehicle and develop a dynamic map. If an obstacle is detected the system plans a route around it. Current UAV’s cannot fly low to the ground because they lack a system like this. This new system is planned for deployment in unmanned medical rescue helicopters.
Probably also for highly tactical seek and destroy missions too, but I will hold out hope that it is only used for the rescue helicopters.