The DGPS technique can be used for navigation over baselines up to approximately 100 km. However, DGPS positioning accuracy is highly correlated and degraded with the extension of its operational range. It is, hence, improper simply to carry on using conventional DGPS for navigation over longer ranges. An approach aimed at providing sufficient accuracy with the use of a minimum network of reference stations, and the modelling of GPS errors, has been proposed and tested for regional navigation over the Taiwan area. It has been shown from the test results that medium-range DGPS based on using multi-reference stations is capable of improving the RMS coordinate differences by 35%, when compared to the use of a single reference station. The RMS values can be further improved by 14% and 6% in plan coordinates and height respectively, when the modelling of atmospheric delay is applied to the differential corrections based on the pseudorange observables collected from the multi-reference stations.