Assessment of BeiDou-2 Orbit and Clock Quality Based on Analysis of Wide-Lane Ambiguities Derived from PPP Models

Abstract

Precise point positioning (PPP) technique has been widely employed for precise positioning as it does not explicitly need any reference stations. The BeiDou satellite navigation system (BDS) helps the technique to achieve more accurate and more robust positioning, particularly when combined with other global satellite navigation systems. The quality of precise orbit and clock is crucial for PPP users. Our earlier study has proved that orbit and clock errors of global positioning system (GPS) can be detected through comparing geometry-free (GF) and geometry-based (GB) wide-lane (WL) ambiguities in PPP model. In this contribution, we will focus on the evaluation of BDS orbit and clock quality. This paper compares and analyzes WL ambiguities derived from the GF and GB model using raw BDS B1 and B2 observations. The methodology is firstly described in order to explain why the differences of these two types of ambiguities can be used as a quality index of orbit and clock. After that, three types of BDS precise orbit and clock products, namely final determined products and real-time predicted and filtering products, are collected and produced. A number of stations in Asia-Pacific regions are selected to derive GF and GB WL ambiguities of each individual BDS satellite for a comparison using these types of orbit and clock products. The results are demonstrated and analyzed in detail. This contribution reveals that our methodology can be used to evaluate the BDS orbit and clock quality at the line-of-sight direction externally and independently in real-time. This is particularly important for real-time users.