An improved system and method for determining a position fix in space and time using the Global Positioning System (GPS) satellite network signals. The system comprises at least three fixed base stations each having a satellite receiver operating in conjunction with a highly accurate (atomic-standard) clock. Each base station's position is known with great accuracy. GPS satellite signals are collected over statistically significant periods of time at each base station and fitted to determine with the clock offset and drift of the station clocks, thus establishing a "network" of base station clocks that in the aggregate is of great accuracy and precision. An arbitrary number of mobile receiver stations similarly collect data for working periods of statistically significant duration; these data are used in conjunction with the base station data to compute position fixes for the mobile stations.