Positioning of radio emission sources with unmanned aerial vehicles using TDOA-AOA measurement processing

Positioning of radio emission sources (RES) with ground and flying network segments exploits interaction of sensors aboard Unmanned Aerial Vehicles (UAVs) with terrestrial stationary ground sensors. Time Difference of Arrival (TDOA) and Angle of Arrival (AOA) measurements processing are the most wide-spread techniques for passive geolocation systems. Successful implementation of TDOA-AOA positioning in existing UAV based geolocation systems achieves accuracy results of tens and hundreds of meters for overoptimistic scenarios without reflections in so called Line of Sight (LOS) conditions. Prevailing application specific cases for UAV based positioning include search and rescue (S&R) operations in mountains, hills and other regions of irregular surface topography with Non-Line of Sight (NLOS) conditions, where radio waves could experience severe reflection and diffraction. For geolocation tasks NLOS problem usually leads to significant errors for both TDOA and AOA measurement processing techniques. Joint processing of TDOA and AOA primary measurements could partially overcome this problem by preliminary identification and exclusion of reflected signals. In current research we refine existing mathematical model and develop new simulation models to investigate NLOS tolerance during positioning with one stationary ground sensor and one sensor aboard flying UAV using joint TDOA-AOA measurement processing technique. The contribution of current research is performance evaluation of considered positioning system with AOA noise and confirmation of its practicability to handle NLOS problem, when AOA deviation is less than 10 degrees. (paper)