Estimation of motion parameters and trajectory of an low flying aircraft using acoustic sensors

Abstract

An aircraft generates an acoustic impulse that propagates outwards from the source. The position of the source and hence the trajectory can be estimated by measuring the relative time of arrival of the impulse at a number of spatially distributed sensors. The time difference for the acoustic wave front to arrive at two spatially separated sensors is estimated by cross correlating the digitized outputs of the sensors. The time delay estimate is used to calculate the source bearing and the position of the source is found using triangulation technique using the bearings from two widely separated receiving nodes. The flight parameter of the aircraft is obtained by autocorrelation method using acoustic Multipath delays. The signal emitted by an UAV arrives at a stationary sensor located above a flat ground via a direct path and a ground-reflected path. The difference in the times of arrival of the direct path and ground-reflected path signal components is known as the Multipath delay. A model is developed to predict the variation with time and autocorrelation method is formulated to estimate the motion parameters like speed and altitude of the aircraft.