Improvement of PPP-inferred tropospheric estimates by integer ambiguity resolution

Abstract

Integer ambiguity resolution in Precise Point Positioning (PPP) can improve positioning accuracy and reduce convergence time. The decoupled clock model proposed by Collins (2008) has been used to facilitate integer ambiguity resolution in PPP, and research has been conducted to assess the model’s potential to improve positioning accuracy and reduce positioning convergence time. In particular, the biggest benefits have been identified for the positioning solutions within short observation periods such as one hour. However, there is little work reported about the model’s potential to improve the estimation of the tropospheric parameter within short observation periods. This paper investigates the effect of PPP ambiguity resolution on the accuracy of the tropospheric estimates within one hour.The tropospheric estimates with float and fixed ambiguities within one hour are compared to two external references. The first reference is the International GNSS Service (IGS) final troposphere product based on the PPP technique. The second reference is the Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC) radio occultation (RO) event based on the atmospheric profiles along the signal travel path. A comparison among ten co-located ground-based GPS and space-based RO troposphere zenith path delays shows that the mean bias of the troposphere estimates with float ambiguities can be significantly reduced from 30.1 to 17.0mm when compared to the IGS troposphere product and from 36.3 to 19.7mm when compared to the COSMIC RO. The root mean square (RMS) accuracy improvement of the tropospheric parameters by the ambiguity resolution is 33.3% when compared to the IGS products and 44.3% when compared to the COSMIC RO. All these improvements are achieved within one hour, which indicates the promising prospect of adopting PPP integer ambiguity resolution for time-critical applications such as typhoon prediction.