PRELIMINARY EVALUATION OF THE RUSSIAN GLONASS SYSTEM AS A POTENTIAL GEODETIC TOOL

By the beginning of 1996 the Russian Global Navigation Satellite Syste m (GLONASS) constellation was completely deployed, although several sa tellites have already been decommissioned since then. With 17 satellit es in operation (status as of 21 December 1997, although two of them a re unusable and one is a nonoperative spare), GLONASS is now an altern ative and a complement to GPS. We present an evaluation of the current status of the GLONASS system, paying particular attention to its poss ible geodetic applications. Data from several receivers were used for this evaluation, including data from GPS receivers in order to allow f or a comparison between GLONASS and GPS. We tested the quality of the geodetic observables, the consistency of the broadcast orbits, the sin gle-point positioning results, and we also looked at multipath errors and cycle slips in our GLONASS data. In general the GLONASS performanc e has been found to be very satisfactory, even better than GPS in aspe cts such as single-receiver positioning or in the quality of the secon d-frequency pseudo-ranges due to the degradation of the GPS measuremen t quality under selective availability and anti-spoofing.