Real Time Satellite Clocks in Single Frequency Precise Point Positioning

Kurzfassung

Computing a position with Single Frequency Precise Point Positioning (SF-PPP) algorithms compels to the use of satellite clock corrections, and for use with real-time applications, only a limited set of sources for orbit and clock data is available, for example the predicted Ultra Rapid products of the International GNSS Service (IGS). Recently, real-time clock estimates with a latency of only a few seconds have become available. They are more accurate than the predicted Ultra Rapid corrections . Used in this paper are the real-time clock estimates computed with the REal-TIme CLock Estimation (RETICLE) system, which has been developed at German Space Operations Center of the German Aerospace Center (GSOC/DLR). These clock products are globally valid and disseminated to real-time users via NTRIP-streams from a caster. In this research, first a comparison is made in the satellite clock error domain as the real-time RETICLE and predicted Ultra Rapid corrections are compared to the Final IGS clock corrections. Weighted over the four different types of GPS satellites the empirical standard deviation of clock differences between Final and RETICLE clocks become less than 0.4 nanosecond. Differences between Final and Ultra Rapid clocks lead to a standard deviation of around 2 nanoseconds. Secondly the single frequency precise point positioning position errors in the North, East and Up directions are investigated. With the use of the RETICLE clocks the empirical standard deviation of the position errors in the North and East directions are between 2 and 3 decimeter and in the Up direction around 5 decimeter. The 95% errors become 6 decimeter in the horizontal direction and 9 decimeter in the vertical. These results are comparable with the accuracies reached when using Final products.