Abstract
Recent developments in GPS positioning show that a user with a standalone GPS receiver can obtain positioning accuracy comparable to that of carrier-phase-based differential positioning. Such a technique is commonly known as precise point positioning (PPP). A significant challenge of PPP, however, is that it typically requires a minimum of 30 minutes to achieve centimeter- to decimeter-level accuracy. This relatively long convergence time is the result of un-modeled GPS residual errors. This paper addresses error mitigation techniques to achieve near real-time PPP at sub-decimeter-level accuracy.
In this research, we developed between-satellite single-difference PPP algorithms to cancel out the receiver clock error, receiver initial phase bias, and receiver hardware delay. The decoupled clock corrections, provided by Natural Resources Canada (NRCan), were also applied to account for satellite hardware delay and satellite initial phase bias.
The results showed that the improvement obtained through the implementation of the decoupled clock correction in the BSSD model is only about 10%, which reflects the stability of the satellite hardware delays in comparison with that of the receiver hardware delays. In addition, it was found that between-satellite single-difference using the decoupled clock corrections improves the standard deviation of the estimated coordinates by more than 60% and improves the convergence time of the estimated coordinates by about 50%.