Improving real-time precise point positioning ambiguity resolution by considering uncalibrated phase delay uncertainty

Abstract

Precise Point Positioning with Ambiguity Resolution (PPP-AR) is a crucial technology for real-time, centimeter-level positioning. However, when using the Least squares AMBiguity Decorrelation Adjustment (LAMBDA) method for integer ambiguity resolution, the uncertainty of Uncalibrated Phase Delay (UPD) correction is not considered at present. As a consequence, discrepancies arise between the ambiguity variance–covariance matrix of the PPP float solution and the precision of the real-valued ambiguities after UPD correction. To address this issue, we investigate the effect of incorporating UPD uncertainty into PPP-AR and implement an ambiguity-domain scheme that uses this uncertainty to assist integer ambiguity resolution. The satellite UPD residuals were used to represent the uncertainty of satellite UPD and improve the performance of PPP-AR. Experiments were conducted using data collected over a 14-day period from 122 reference stations distributed across China. The results demonstrate that accounting for UPD uncertainty can significantly enhance PPP-AR performance. In certain epochs, by incorporating UPD uncertainty, vertical positioning errors were reduced from over 15 cm to approximately 1 cm, while horizontal positioning errors decreased from decimeter-level to 1.2 cm. During ionospheric active periods, the new method also notably shortened the convergence time of PPP-AR. Under 0, 10, and 20 s delays in receiving real-time satellite orbit and clock offset products, the application of the UPD uncertainty reduced the convergence time in the vertical direction by 9.54 %, 10.97 %, and 13.58 %, respectively.