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The integrated use of GPS/GLONASS observations in network code differential positioning

Przestrzelski, Paweł; Bakuła, Mieczysław; Galas, Roman

FG Präzisionsnavigation und -ortung

We present the methodology and results of GPS/GLONASS integration in network code differential positioning for regional coverage across Poland using single frequency. Previous studies have only concerned the GPS system and relatively short distances to reference stations of up to tens of kilometers. This study is limited to using GPS and GLONASS. However, the methodology presented applies to all satellite navigation systems. The deterministic and stochastic models, as well as the most important issues in GPS/GLONASS integration are discussed. Two weeks of the GNSS observations were processed using software developed by the first author. In addition to interpolation of pseudorange corrections (PRCs) within the polygon of reference stations, the effect of their extrapolation outside that polygon is also briefly presented. It is well known that the positioning accuracy in a network of heterogeneous receivers can be degraded by GLONASS–FDMA frequency-dependent hardware biases. Our research reveals that when using such networks, the effect of these biases on the network differential GNSS (NDGNSS) positioning results as derived from both GPS and GLONASS can be reduced by simple down-weighting of GLONASS observations. We found that the same approach for the homogeneous equipment is not required; however, it can enhance performance of NDGNSS. Yet, the addition of the down-weighted GLONASS pseudoranges still improves the positioning accuracy by 14–25 %. The representative NDGNSS estimation is characterized by 0.17, 0.12 and 0.32 m RMS errors for the north, east and up component, respectively.