Comparison of community and commercial DGPS correction sources in Tasmania, Australia

Differential Global Positioning System (DGPS) observations are utilised for a wide range of applications. Users take their accuracy requirements into consideration when selecting from available observables, either in real-time or in post-processed mode. These accuracy requirements range from metres to millimetres and are closely linked to economic considerations, since the cost of the necessary hardware varies significantly. This study investigates and compares several pseudo-range data sources available in Tasmania, Australia, either at a cost or free of charge. The quality of the differential data and correction sources is assessed by determining accuracy relative to the State's primary geodetic control network as a function of distance from reference receivers. Datum differences are routinely overlooked by practitioners utilising code measurements, hence we quantify how this affects the accuracy achievable with real-time pseudo-range based DGPS services. Simple coordinate shifts are proposed to effectively consider these datum differences in practice for sub-metre pseudo-range DGPS positioning in Tasmania. A comparison to the accuracy achievable with available carrier phase based correction data sources is also presented.