A method acquires a location system signal that includes second data signals superimposed on the first data signals. The method includes iterating Doppler frequency offset values and time offsets to generate error signals, each representing a difference between summed consecutive correlation values and a corresponding estimated ideal value. Each error signal corresponds to a different time offset and an associated time period. The second data signal has a bit edge that occurs during the time period of each of the sums of consecutive correlation values. The presence of a bit edge during an associated time period increases the error signal. A measure of the minimum error is used to identify a time offset value that is used to develop a first determined Doppler frequency offset. A Kalman filter refines the first determined Doppler frequency offset.