Global positioning system (GPS) precise positioning using carrier phase measurements can provide accurate kinematic positioning results, which have been widely applied to geodesy and geophysics researches. Ambiguity resolution (AR) is the procedure to resolve double-differenced (DD) integer ambiguity on the phase measurements and is the key to achieve high-accuracy positioning results. GPS measurement errors critically affect the AR performance. The error sources comprise measurement random noise and systematic errors such as multipath, orbital biases, and atmospheric delays. In the least-squares process, the use of an increased sampling rate can improve the measurement redundancy and mitigate the influence of random noise on the unknown parameters including ambiguity parameters; however, it cannot effectively reduce the influence of systematic errors on the unknown parameters because the systematic errors are mostly correlated in time. As a result, the use of an increased sampling rate is not regarded as a crucial means to refine GPS AR. Compared with GPS, combined global navigation satellite systems (GNSS) can provide enhanced satellite availability, which is a well-known factor for AR improvement. Furthermore, combined GNSS can provide better external reliability in the least-squares process to reduce the influence of systematic errors on the unknown parameters. It is therefore expected that an increased sampling rate can lead to further improved combined GNSS AR performance. Given the fact that the impact of sampling rate on combined GNSS AR has not been assessed before, we develop a generalized method to carry out stand-alone GPS and combined GNSS (GPS, GLONASS and BDS) AR with different sampling rates ranging from 0.05 to 1 Hz. The experimental results show that (1) combined GNSS AR is, as expected, more reliable than GPS AR at the same sampling rate by virtue of the enhanced satellite availability; (2) combined GNSS notably improves the accuracy of kinematic positioning results in the horizontal and vertical directions; (3) using an increased sampling rate effectively further improves combined GNSS AR. As a result, in order to achieve optimized AR performance in kinematic positioning, it is crucial to use combined GNSS together with a high sampling rate.
All Science Journal Classification (ASJC) codes
- Aerospace Engineering
- Space and Planetary Science