Multiple Carrier Ambiguity Resolution and Performance Benefits for RTK and PPP Positioning Services in Regional Areas

Based on original code and phase measurements to three or more ranging signals offered by future GNSS systems, this paper outlines geometry-free and geometry-based ambiguity resolution (AR) strategies for DD phase measurements and introduces the algorithms that improve estimation of zero-differenced (ZD) phase biases using a network of GNSS reference stations. Given three L-band frequencies, AR strategies can generally identify two best Extra-widelane (EWL: λ≥293cm, in this context) or Widelane (WL: 75cm ≤λ<293cm) virtual signals to allow for more reliable ambiguity resolution, thus supporting decimetre RTK positioning over baselines of hundreds of kilometres in length. Analysis shows that the success rates for these selected virtual signals, having minimal or near minimal ionospheric effects and low noise levels, can be easily over 90% with measurements from a signal epoch. The third virtual signal has to be a choice of Medium-lane (ML:19cm≤λ<75cm) or Narrow-lane (NL: 10cm ≤λ<19cm) signals, whose integer ambiguity should be performed with refined widelane measurements, to support centimetre RTK positioning over distances of up to a hundred kilometres or so. When the doubledifferenced (DD) integer ambiguities between multiple stations are resolved and fixed, constraints can be imposed to ZD measurements from all the stations to improve the ZD phase bias of each receiver over a short span of observations. Precise ZD measurements are fundamental to enhanced Precise Point Positioning. Numerical experiments using 24-hour dual-frequency GPS data from four US CORS stations, with spacing 21, 56 and 74km, were performed in order to demonstrate the performance benefits of some of the key algorithms