An apparatus and method begin creation and storage of correlation sums to be demodulated (“early-collected sums”) prior to determination of a location of a bit of data in a wireless signal relative to a local clock. Such early storage allows demodulation of these early-collected sums at a later time, specifically on determination of the data's location in the wireless signal, thereby to yield early-collected data bits. Additionally, after determination of the data bit's location in the wireless signal, additional data bits are further generated in the normal manner, by demodulating the wireless signal, thereby to yield normally-collected data bits. Use of early-collected data bits in generating navigation data reduces the time to start data demodulation, and enables fewer normally-collected data bits to be used to generate navigation data, in several aspects of the invention.