1. An unmanned vehicle system, comprising: at least one autonomous ground vehicle operable to autonomously navigate across the ground; wherein the autonomous ground vehicle has a set of on-board on-ground perception sensors, which have a field of view that contains at least a portion of the ground ahead of the direction of travel of the ground vehicle; wherein the autonomous ground vehicle further has an on-board on-ground control system; at least one remote controlled aerial vehicle operable to fly in response to commands received from the on-ground control system; wherein the aerial vehicle has on-board in-sky perception sensors having a field of view that contains at least a portion of the ground path to be followed by the ground vehicle wherein the field of view of the on-ground perception sensors further contains the aerial vehicle; where the on-ground control system is operable to locate the aerial vehicle in a frame of reference of the ground vehicle, to receive perception data from the on-ground perception sensors and the in-sky perception sensors, to use the perception data to generate a combined perception area data, and to use the combined perception data to determine a ground path for the autonomous ground vehicle and an aerial path for the aerial vehicle.