Calibrating receiver-type-dependent wide-lane uncalibrated phase delay biases for PPP integer ambiguity resolution

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.

Modeling wide-area tropospheric delay corrections for fast PPP ambiguity resolution

“…The widelane (WL) UPDs are calculated from the Melbourne-Wübbena (MW) combination, and the narrow-lane (NL) UPDs are estimated based on the NL ambiguities derived from IF ambiguities with fixed WL integers, and their usability in UDUC-PPP has been demonstrated by Zhang et al (2019) and Du et al (2020). Generally, N s r,IF is decomposed into the following combination of integer WL N s r,WL and float NL N s r,NL ambiguities for ambiguity fixing (Cui et al 2021). The relationship among the IF, L1, L2, WL, and NL ambiguities can be expressed as follows to understand the principle for UPD estimation at the server and using UPDs for ambiguity fixing at both the server and user.…”

“…Precise point positioning (PPP) (Malys and Jensen 1990;Zumberge et al 1997) is a commonly used technique for real-time Global Navigation Satellite Systems (GNSS) applications that employ precise orbits and clocks derived from the global network to achieve high-precision positioning (Fotopoulos and Cannon 2001). Currently, thanks to the availability of uncalibrated phase delay (UPD) products (Ge et al 2008), the real-time PPP ambiguity resolution (AR) with a convergence time of about 20-30 min can be achieved all over the world (Dow et al 2009;Cui et al 2021). However, the convergence time is still a limiting factor to further promote the real-time PPP applications.…”

Assessment of the performance of GPS/Galileo PPP-RTK convergence using ionospheric corrections from networks with different scales

“…The optimal integer solution for SD NL ambiguities can be found by applying the least-square ambiguity decorrelation adjustment (LAMBDA) method (Teunissen 1995). Since the residual model errors can affect the fractional part of SD NL ambiguities, ambiguity validation is particularly important to fix SD NL ambiguities reliably (Ge et al 2008;Cui et al 2021). Specifically, for ambiguity validation, the ratio and bootstrapping success rate are frequently utilized for AR (Ji et al 2010;Verhagen 2005Verhagen , 2003Li and Zhang 2015).…”

Precise position determination of USV based on the IF combination and un-combined PPP ambiguity resolution model

“…Nevertheless, the UC model has also become popular for users, especially for multifrequency and multisystem applications (Li et al 2018, Liu et al 2017b, Su et al 2020. Fortunately, research has shown that a reasonable transformation can achieve the uniformity of the two function models (Cui et al 2021, Du et al 2020a.…”