Abstract
Wide-lane (WL) uncalibrated phase delay (UPD) is usually derived from Melbourne–Wübbena (MW) linear combination and is a prerequisite in Global Navigation Satellite Systems (GNSS) precise point positioning (PPP) ambiguity resolution (AR). MW is a linear combination of pseudorange and phase, and the accuracy is limited by the larger pseudorange noise which is about one hundred times of the carrier phase noise. However, there exist inconsistent pseudorange biases which may have detrimental effect on the WL UPD estimation, and further degrade user-side ambiguity fixing. Currently, only the large part of pseudorange biases, e.g., the differential code bias (DCB), are available and corrected in PPP-AR, while the receiver-type-dependent biases have not yet been considered. Ignoring such kind of bias, which could be up to 20 cm, will cause the ambiguity fixing failure, or even worse, the incorrect ambiguity fixing. In this study, we demonstrate the receiver-type-dependent WL UPD biases and investigate their temporal and spatial stability, and further propose the method to precisely estimate these biases and apply the corrections to improve the user-side PPP-AR. Using a large data set of 1560 GNSS stations during a 30-day period, we demonstrate that the WL UPD deviations among different types of receivers can reach ± 0.3 cycles. It is also shown that such kind of deviations can be calibrated with a precision of about 0.03 cycles for all Global Positioning System (GPS) satellites. On the user side, ignoring the receiver-dependent UPD deviation can cause significant positioning error up to 10 cm. By correcting the deviations, the positioning performance can be improved by up to 50%, and the fixing rate can also be improved by 10%. This study demonstrates that for the precise and reliable PPP-AR, the receiver-dependent UPD deviations cannot be ignored and have to be handled.
Highlights
Precise point positioning (PPP) is a high-precision positioning technique using a stand-alone receiver (Zumberge et al 1997) and has been widely used for scientific research and civilian applications
We present a data processing strategy to investigate the inconsistency of WL uncalibrated phase delay (UPD) estimated from different receiver types caused by the related pseudorange biases and an approach to estimate and calibrate the UPD differences to improve the WL ambiguity fixing in PPP
The experiment demonstrates that WL UPDs estimated from different receiver types could be different remarkably; for example, there are large deviations up to 0.3 cycles between the same Trimble receiver with different firmware versions
Summary
Precise point positioning (PPP) is a high-precision positioning technique using a stand-alone receiver (Zumberge et al 1997) and has been widely used for scientific research and civilian applications. The observablespecific signal bias is proposed for the pseudorange biases (Wang et al 2020), but further investigation still needs to be carried out to take into account the different receivers Such satellite-specified pseudorange biases are detected, neither their effect on WL UPDs estimation nor their impact on PPP-AR has been investigated or evaluated so far, probably because such biases are considered to be small and negligible compared to the pseudorange noise and WL wavelength. Such a bias of 20 cm will shift the corresponding WL ambiguity by about 0.25 cycles and makes its reliable fixing difficult and even impossible. PPP-AR with and without such calibration is performed and compared to demonstrate the impact of this receiver-dependent deviation
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