Coordinate Noise Reduction by Estimating Wide-Lane Phase Bias for Ambiguity Resolution in GipsyX/RTGx using Non-JPL Multi-Constellation Products

Double-differenced phase bias ambiguities are frequently resolved to integer values to strengthen solution geometry and minimise the noise of other parameter estimates. The GipsyX/RTGx GNSS software uses Wide-Lane Phase Bias (WLPB) information for ambiguity resolution (AR) while point positioning a single local receiver using JPL's GPS-only orbit/clock product. The limitation of the current JPL WLPB is that researchers cannot use it for multi-GNSS solutions, and cannot perform AR when using non-JPL products. Instead, we have modeled the WLPB with non-JPL products e.g., CODE using a global network of GNSS sites, which enables combined GPS AR and GLO float solutions. We tested WLPB performance using PPP/AR on globally distributed stations at varying latitudes, and assessed the performance based on position shift and precision. We also analysed the latitude dependency of the noise content in each solution set at periods/frequencies related to the constellation geometry and tidal errors. The results show no position shift in any coordinate components between AR solutions using JPL's WLPB and those using our estimated WLPB with JPL products. A small (0.1 mm) position shift resulted between float and AR solutions using WLPBs formed with the CODE orbit/clock product, which is also within the range of 0.1 mm shown between float and AR solutions using JPL products. There are 32, 5 and 0% precision improvements in the respective E, N and U components of GPS-only AR CODE solutions compared with the CODE float solutions. There is also a 19, 5 and 5% improvement in the precision of the E, N and U components of GPS+GLO CODE solutions, respectively, when the GPS ambiguities are fixed. The lower precision may be due to the limited number of receivers used in our test WLPB estimation network. Also, except for the 7.80, 13.67, and 14.76-day periods, we observe a coordinate noise power reduction with increased latitude, especially in the E and U components.