Abstract: A method and apparatus for measuring the time difference of arrival between two received signals, each received signal being a time delayed version of a transmitted signal as intercepted at two different sensors where the transmitted signal is generated by a radio frequency transmitter. The apparatus includes a sensor having a receiver which receives a received signal and generates a receiver output signal, a decoder which decodes an encoded signal transferred from another sensor to generate a reconstructed signal representative of the transmitted signal received at the other sensor and a correlator for correlating the reconstructed signal and the receiver output signal to determine a time difference of arrival of the receipt of the transmitted signal at the respective sensors.