A method of determining a location of an event of interest by processing signals from a satellite positioning system. The method comprises receiving recorded blocks of data samples of a satellite broadcast including blocks recorded at the approximate location of the event of interest, each block including one or more timestamps generated within a first portable device at which the samples were recorded; receiving a time of occurrence of the event recorded independently of the samples; comparing the timestamps and the time of occurrence to identify at least one block corresponding to the event; and processing the data samples of the identified at least one block to derive position information approximating the location of the event.