Methods and systems for frequency synchronizing base stations in a cellular communication system. In one aspect of the invention, a method to measure a frequency related to a base station of a cellular communication system includes receiving a satellite positioning system signal; determining a frequency of a reference signal from a local oscillator of a mobile station from the satellite position system signal; receiving a first cellular signal from a base station containing first and second timing markers; determining first and second time tags for the markers using the reference signal; and combining the frequency of the reference signal and the first and second time tags to compute a first frequency related to the base station.