An accurate radio frequency ranging system is provided for measuring the time required for a signal to be transmitted from a ground station to a remote station and to be returned to the ground station. The ground station is provided with a master reference clock that is employed to drive a first pseudonoise generator. The ranging system in the ground station is started by a unique and predetermined start epoch signal produced by the first pseudonoise generator. The first pseudonoise generated signals are transmitted to the remote station where they are tracked and sensed. When the original start epoch signal is sensed at the remote station, it is employed as a trigger or read signal to initiate the generation of a stop epoch signal. The stop epoch signal is retransmitted to the ground station and stored in a register where it is compared with pseudonoise generated signals being retransmitted from the remote station to the ground station. When the correlation between the two signals occurs, a new epoch stop signal is produced which stops the timing of the ranging system in the ground station. Since the pseudonoise generated signals transmitted from the remote station to stop the ranging system in the ground station are not locked on to the pseudonoise signals being transmitted from the ground station to the remote station, there is no requirement for turn-around coherency.