Multi-frequency Multi-GNSS PPP: A Comparison of Two Ambiguity Resolution Methods

A major limitation of the GNSS Precise Point Positioning (PPP) technique is the slow solution convergence time. Tens of minutes are required for the solutions to converge to decimetre-level accuracy even with ambiguity resolution (PPP-AR). This paper analyses two ambiguity resolution methods to provide reliable ambiguity resolution and fast PPP convergence time. They are the partial ambiguity resolution based-LAMBDA method (PAR-Ps) and the iFlex method proposed by Trimble Navigation company. One month of multi-frequency GNSS observations from one CORS station was processed in kinematic mode. The root mean square (RMS) results indicate that the iFlex method outperforms the PAR-Ps method with respect to minimising the position errors of a kinematic test. Although two methods provide a similar horizontal convergence time (one minute), the horizontal error using the PARPs is not stable until the 13-minute mark. This is caused by several sessions with incorrectly-fixed ambiguities. When compared to the PAR-Ps method, the iFlex method has improved the vertical convergence time to about 7 minutes.