Vehicle location system

Signals from a number of NAVSTAR global positioning system (GPS) satellites (11,12,13,14) are received by a receiver (16) in a vehicle (15) and a segment of the signals is stored in a memory (18) prior to retransmission by a transmitter (19). A base station (35) receives these transmissions from the mobile unit using a first receiver (36) as well as receiving signals directly from the NAVSTAR GPS satellites (11,12,13,14) using a second receiver (38). A control and calculating means (37) within the base station (35) can determine the ephemeris (course) information for the satellites and measure the transmission times or propagation delays of signals between the satellites and the vehicle and with this information the control and calculating means (37) can calculate the position of the vehicle unit.