Abstract
The use of the GLONASS legacy signals for real-time kinematic positioning is considered. Due to the FDMA multiplexing scheme, the conventional CDMA observation model has to be modified to restore the integer estimability of the ambiguities. This modification has a strong impact on positioning capabilities. In particular, the ambiguity resolution performance of this model is clearly weaker than for CDMA systems, so that fast and reliable full ambiguity resolution is usually not feasible for standalone GLONASS, and adding GLONASS data in a multi-GNSS approach can reduce the ambiguity resolution performance of the combined model. Partial ambiguity resolution was demonstrated to be a suitable tool to overcome this weakness (Teunissen in GPS Solut 23(4):100, 2019). We provide an exhaustive formal analysis of the positioning precision and ambiguity resolution capabilities for short, medium, and long baselines in a multi-GNSS environment with GPS, Galileo, BeiDou, QZSS, and GLONASS. Simulations are used to show that with a difference test-based partial ambiguity resolution method, adding GLONASS data improves the positioning performance in all considered cases. Real data from different baselines are used to verify these findings. When using all five available systems, instantaneous centimeter-level positioning is possible on an 88.5 km baseline with the ionosphere weighted model, and on average, only 3.27 epochs are required for a long baseline with the ionosphere float model, thereby enabling near instantaneous solutions.
Highlights
With the exception of the Russian GLONASS, all current satellite navigation systems such as GPS, Galileo, BeiDou, and QZSS make use of the code division multiple access (CDMA) scheme to separate the signals from different satellites at the user receiver
We focus on combined multi-GNSS solutions and give a detailed analysis of the capabilities of this new frequency division multiple access (FDMA) model for single baseline real-time kinematic (RTK) positioning for combinations of up to five systems
While the formal positioning precision of the FDMA model was shown to be comparable to the CDMA model, its ambiguity resolution capabilities are clearly inferior
Summary
With the exception of the Russian GLONASS, all current satellite navigation systems such as GPS, Galileo, BeiDou, and QZSS make use of the code division multiple access (CDMA) scheme to separate the signals from different satellites at the user receiver. Combining systems strongly improves the RTK positioning capabilities, as was demonstrated for GPS and Galileo (Tiberius et al 2002; Julien et al 2003; Odijk et al 2012), GPS and BeiDou (Deng et al 2014; He et al 2014; Teunissen et al 2014; Zhao et al 2014; Odolinski et al 2015b), and four-system GPS, Galileo, BeiDou, and QZSS (Odolinski et al 2015a) Such improvement can occur when including GLONASS FDMA data (Teunissen and Khodabandeh 2019; Hou et al 2020), but it is shown that the ambiguity resolution performance can be clearly reduced compared to the case without GLONASS. The variances of the BIE estimates can serve as benchmark results for analyzing the best possible performance of any given model
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