1. An unmanned vehicle system, comprising: at least one autonomous ground vehicle operable to autonomously navigate across ground on a surface of the earth in a direction of travel; 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 autonomous ground vehicle in its a direction of travel; 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 an aerial path in response to flight commands received from the on-board on-ground control system; wherein the aerial vehicle has a communications interface for receiving the flight commands; wherein the aerial vehicle carries in-sky perception sensors having a field of view that contains at least a portion of a ground path to be followed by the autonomous ground vehicle wherein the field of view of the on-board on-ground perception sensors further contains the aerial vehicle; where the on-board on-ground control system further has a perception process that receives perception data from the on-board on-ground perception sensors and perception data from the in-sky perception sensors, and further has a localization process that uses the perception data to locate the aerial vehicle in a frame of reference of the autonomous ground vehicle, and further has a perception area process that combines the perception data; and further has a movement manager process that uses the combined perception data to determine the ground path for the autonomous ground vehicle and an aerial path for the aerial vehicle; wherein the movement manager process calculates at least part of the ground path in response to perception data from the in-sky perception sensors, and further calculates at least part of the aerial path in response to perception data from the on-board on-ground perception sensors.