Patent attributes
Propagation time for a target signal path is determined by detecting and processing a plurality of unknown signals received at two locations. A third location is established, such that the propagation time between the third location and one of the two locations is known, and the signal path between the third location and the other of the two locations is the target signal path. The two locations are monitored for any signals that may be detected. Signals received at the two locations are processed to determine which signals have a common source, and of the signals having a common source, the signal having the greatest delay between times of reception at the two locations is selected. The selected signal is used to determine the propagation time between the two locations.