Emitter Geolocation with Two UAVs

Abstract

In geolocation with multiple UAVs, a minimum of three UAVs is required when the transmitter is known to be on the ground and four if the altitude of the transmitter is not known. In each case the estimates are based on time-dijference-of-arrivals (TDOA) of a single pulse at the UAVs. While this concept is easy to demonstrate, there are a number of obstacles towards practical implementation. They include: (i) the need to determine UAV trajectories for optimal geolocation, (ii) the need for an association algorithm capable of grouping together measurements from a common pulse given the sheer number of pulses that are detected by each UAV, and, (Hi) the need for a suitable low bandwidth communication network for measurement transfer. The complexity of each of these problems is prohibitive when three or more netted UAVs have to be deployed but could be manageable with a simpler system consisting of two netted UAVs in which geolocation is achieved by processing multiple TDOA measurements collected over time by the UAVs as they traverse the surveillance region. When a pulse is detected by the two UAVs, a range difference is generated and a processing algorithm then converts it to an appropriate set of 2D measurement components that lie on a hyperbola. Over time these measurements or their components are used to initiate and update emitter track components using an unscented Kalman filter or a Kalman filter in conjunction with Gaussian sum approximation. By employing a suitable pruning technique, track components not supported by the incoming measurements are eliminated.