Abstract text

A system includes first and second transmitters attachable to first and second vehicles. The transmitters can each transmit successive signals at predetermined time intervals. Tracking stations at different locations are configured to receive the signals transmitted by at least one of the first and second transmitters, distinguish signals transmitted by the first transmitter from signals transmitted by the second transmitter, and determine from the transmitted signals respective position information for at least one of the first and second transmitters. Each of the tracking stations is further configured to be in signal communication with at least one other of the tracking stations. The system further includes at least one processing device in signal communication with at least one of the tracking stations. The processing device is configured to determine from the position information a location of the first vehicle relative to a location of the second vehicle.