Design features of D-GNSS reference stations

Differential GPS (DGPS) navigation systems have been in use for several years now in order to improve upon the stand-alone GPS navigation accuracy capability and, to a limited extent, integrity. Such systems became even more important with the introduction of the US DoD´s selective availability (SA) policy, whereby unauthorised users are denied access to the full GPS accuracy. Since the emergence of conventional or local DGPS, further concepts, covering larger areas, have evolved. Networked differential augmentation systems (NDASs) have been employed to provide improvements in navigation accuracy over areas as large as the North Sea. The wide area differential (WAD) augmentation concept represents further improvement and is capable of providing both integrity and correction information over an entire continental region, or even globally. A fundamental part of any differential system is the reference station (RS), upon which all the integrity and differential correction information is based. In general, the RS architecture should take into account various important points relating to requirements for site location, hardware and software, potential for self-monitoring, data archiving and checking, availability and continuity of operation, etc. There is a fundamental need for a generic design capable of being used in any situation. There is a need to develop an expandable and inter-operable RS architecture. This paper discusses some of the issues which should be considered in order to realise such an architecture