Abstract
Ambiguity Resolution in Precise Point Positioning (PPP-AR) is important to achieving high-precision positioning in wide areas. The International GNSS (Global Navigation Satellite System) Service (IGS) and some other academic organizations have begun to provide phase bias products to enable PPP-AR, such as the integer-clock like products by Centre National d’Etudes Spatials (CNES), Wuhan University (WUM) and the Center for Orbit Determination in Europe (CODE), as well as the Uncalibrated Phase Delay (UPD) products by School of Geodesy and Geomatics (SGG). To evaluate these disparate products, we carry out Global Positioning System (GPS)/Galileo Navigation Satellite System (Galileo) and BeiDou Navigation Satellite System (BDS-only) PPP-AR using 30 days of data in 2019. In general, over 70% and 80% of GPS and Galileo ambiguity residuals after wide-lane phase bias corrections fall in ± 0.1 cycles, in contrast to less than 50% for BeiDou Navigation Satellite (Regional) System (BDS-2); moreover, around 90% of GPS/Galileo narrow-lane ambiguity residuals are within ± 0.1 cycles, while the percentage drops to about 55% in the case of BDS products. GPS/Galileo daily PPP-AR can usually achieve a positioning precision of 2, 2 and 6 mm for the east, north and up components, respectively, for all phase bias products except those based on German Research Centre for Geosciences (GBM) rapid satellite orbits and clocks. Due to the insufficient number of BDS satellites during 2019, the BDS phase bias products perform worse than the GPS/Galileo products in terms of ambiguity fixing rates and daily positioning precisions. BDS-2 daily positions can only reach a precision of about 10 mm in the horizontal and 20 mm in the vertical components, which can be slightly improved after PPP-AR. However, for the year of 2020, BDS-2/BDS-3 (BDS-3 Navigation Satellite System) PPP-AR achieves about 50% better precisions for all three coordinate components.
Highlights
As a high-precision positioning technique which is independent of nearby reference stations, Global Navigation Satellite System (GNSS) Precise Point Positioning (PPP) has been applied widely to achieve millimeter-level static positioning (Zumberge et al, 1997)
The phase bias products based on GBM satellite orbits and clocks (i.e., GRG-gbm and SGGgbm) deliver the lowest improvement rates after PPP Ambiguity Resolution (PPP-AR)
In the case of hourly static Global Positioning System (GPS)/Galileo Navigation Satellite System (Galileo) solutions, both east and north components can have more than 30% improvement in terms of positioning precisions, while again the GRG-gbm and School of Geodesy and Geomatics (SGG)-gbm products show inferior performance compared to others
Summary
As a high-precision positioning technique which is independent of nearby reference stations, Global Navigation Satellite System (GNSS) Precise Point Positioning (PPP) has been applied widely to achieve millimeter-level static positioning (Zumberge et al, 1997). Ge et al (2008) computed receiver- and satellite-dependent Uncalibrated Phase Delays (UPD) and fixed single-receiver ambiguities to their integer candidates successfully. Wide-lane UPDs were estimated as a constant over 24 h using the Melbourne–Wübbena (MW) combination observations (Melbourne, 1985; Wübbena, 1985). Narrow-lane UPDs were estimated over shorter intervals, e.g.,15 min. While the UPD method used the International GNSS Service (IGS) legacy clock products, Laurichesse et al (2009) and Collins et al (2010) formulated “integer clocks” by absorbing narrow-lane UPDs into the legacy satellite clocks. To mitigate possible biases introduced into pseudorange after applying the integer clocks, Laurichesse et al (2009) aligned the integer clocks with the legacy clocks to an offset of smaller than half
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