Passive acoustic localization of small aircraft

Low Flying Aircraft (LFA) may be used to smuggle illicit drugs or illegal immigrants across borders. Stevens Institute of Technology has built Acoustic Seismic Aircraft Detection (ASAD) system that demonstrated detection, tracking and classification of LFA by their radiated noise using passive acoustic sensors. It consists of several nodes deployed in a wide area, where each node acquires signals from an attached cluster of five microphones. This paper presents the basics of the methodology of target localization using this specific setup, based on the direction of arrival (DOA) finding sensors followed by triangulation of the direction of arrival estimates from two or more nodes. DOA is found using the time difference of arrival (TDOA) estimates from several pairs of microphones. Software for prediction of performance was developed and was used to provide accuracy of localization estimation in field tests. The field tests were conducted with various types of LFA Cessna, Helicopter, ultralight and the acoustic tracking results were compared with GPS ground truth.