Abstract
Several processing strategies that use dual-frequency GPS-only solution, multi-frequency Galileo-only solution, and finally tightly combined dual-frequency GPS + Galileo solution were tested and analyzed for their applicability to single-epoch long-range precise positioning. In particular, a multi-system GPS + Galileo solution was compared to GPS double-frequency solution as well as to Galileo double-, triple-, and quadruple-frequency solutions. Also, the performance of the strategies was analyzed under clear-sky and obstructed satellite visibility in both single-baseline and multi-baseline modes. The results indicate that tightly combined GPS + Galileo instantaneous positioning has a clear advantage over single-system solutions and provides an accurate and reliable solution. It was also confirmed that application of multi-frequency observations in case of Galileo system has an advantage over a dual-frequency solution.
Highlights
The key factor in relative positioning is the resolution of double-differenced ambiguities
Several processing strategies based on processing of dualfrequency GPS-only signals, dual-to quadruple-frequency Galileo-only signals, and tightly combined processing of GPS ? Galileo signals were tested and analyzed for their applicability for long-range precise instantaneous positioning
The best results were always obtained with combined processing of GPS ? Galileo signals in a multi-station solution
Summary
The key factor in relative positioning is the resolution of double-differenced ambiguities. The most challenging task is the correct ambiguity resolution using data from a single epoch in instantaneous positioning Two overlapping frequencies (1 575.420 MHz for L1/GPS and E1/ Galileo, and 1 176.450 MHz for L5/GPS and E5a/Galileo) will allow creating double-differenced observations between the both systems This will result in tightly combined processing, taking into account time, coordinate system differences, and receiver inter-system biases (Odijk et al 2012). A reliable ambiguity resolution based on single-epoch data, in comparison with the on-thefly approach, is an extremely difficult and challenging task due to the low number of observations and the lack of change in satellite geometry (Hu et al 2005, Cellmer et al 2010; Paziewski et al 2013). The numerical tests presented are based on simulated GNSS observational data (hardware simulator) and in-housedeveloped post-processing software—GINPOS (GNSS instantaneous positioning software) (Paziewski 2012)
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