Abstract: A method and apparatus for detecting targets. A sound wave within an underwater detection region is transmitted from each of a number of sources. The sound wave transmitted by each of these sources comprises a pulse train of identical pulses. Pulses are received at a receiver within the underwater detection region. Data is generated in response to receiving the pulses. Correlation data for the pulses is generated based on the data generated by the receiver. A determination is made as to whether each of the pulses received at the receiver is received from a target located within the underwater detection region or from one of the number of sources.

Abstract: A method and apparatus for detecting an aircraft. The method is provided for wide area tracking of aircraft. An acoustic emission of the aircraft is detected from a plurality of locations. A position of the aircraft at a set of times is estimated by comparing a set of harmonically related Doppler shifted frequencies for the acoustic emission to an expected zero Doppler shifted frequency of the aircraft to form an estimated position. The position of the aircraft and a heading of the aircraft are tracked using the estimated position. The aircraft type is classified based on the corresponding set of zero Doppler frequencies at each acoustic sensor.

Abstract: A method and apparatus for detecting an aircraft. The method is provided for wide area tracking of aircraft. An acoustic emission of the aircraft is detected from a plurality of locations. A position of the aircraft at a set of times is estimated by comparing a set of harmonically related Doppler shifted frequencies for the acoustic emission to an expected zero Doppler shifted frequency of the aircraft to form an estimated position. The position of the aircraft and a heading of the aircraft are tracked using the estimated position. The aircraft type is classified based on the corresponding set of zero Doppler frequencies at each acoustic sensor.

Abstract: The interferometer, which is preferably in the form of a sonar, can have a single projector array and a single receiver array. The projector array comprises a first subset of projector elements that function as a first pseudo projector and a second subset of projector elements that function as a second pseudo projector. One or more of the projector elements belong in both the first and the second subsets, such that one or more of the projector elements function as part of both the first and the second pseudo projectors. A receiver is operative for receiving reflected portions of the signals emitted by the pseudo projectors. A processing system analyzes the signals received by the receiver to at least partially determine the position of an object.