a remotely - controlled unmanned mobile device adapted to function as a robot scout to enter and reconnoiter the site of a disaster and to communicate to a rescue mission information regarding conditions prevailing at the site , making it possible for the mission to decide on rescue measures appropriate to these conditions . the umd is operable in either of two modes . in its air - mobility mode the umd is able to vertically take off and land , to fly to the site and then hover thereover . in its ground - mobility mode , the umd can walk on legs over difficult terrain and through wrecked structures and ruins . the umd is provided with condition - sensitive sensors for gathering data regarding conditions prevailing at the site , and position - sensitive sensors for avoiding obstacles in the path of the walking umd , thereby assuring safe mobility . other sensors govern geo - referenced navigation and flight control functions .