A system for analyzing three-dimensional seismic data includes a plurality of digitizer units, each with a configuration of geophones, a data recording and control center, a base GPS receiver with an associated antenna with a substantially unrestricted view of the sky and at the respective digitizer units low-power slave GPS receivers that acquire and track GPS satellite signals using tracking assistance information provided by the base GPS receiver. The slave GPS receivers use the tracking assistance information to acquire and track GPS satellite signals from which the slave GPS receivers produce associated range information. The system batch processes the range information provided by the slave GPS receivers over an extended period of time to determine the precise positions of the respective slave GPS receivers. The system provides the position information to the slave GPS receivers, and the receivers locally produce associated timing signals that are based on the GPS codes. If a particular slave GPS receiver cannot, at a given time, track any GPS satellite signals, a nearby slave GPS receiver supplies timing information required for the geophone data gathering operations.