Research on GPS precise point positioning with un-differential and un-combined observations

We first introduce GNSS precise point positioning (PPP) based on un-differential uncombined raw pseudo-ranges and carrier phase observations (RAW-OBS-PPP). Then the difference between the traditional PPP based on ionosphere-free dual-frequency combination (LC-PPP) and RAW-OBS-PPP is discussed and evaluated by analyzing mass data of 300 IGS GPS sites during day of year 034~040, 2012. The effects of receiver's DCB and the precision of priori-ionospheric delay on the convergence of RAW-OBS-PPP are focused and discussed in details. For RAW-OBS-PPP, while global ionosphere mapping (GIM) provided by International GNSS Service (IGS) are used as priori-information for ionosphere delays, and the receiver's DCB is estimated, then the mean time is about 13.12 min to take convergence into 10 cm in both north and east components. If no receiver DCB estimated, it needs about 18.48 min. LC PPP and RAW-OBS-PPP have almost the same performance under the condition that GIM is used for RAW-OBS-PPP. If ionosphere delays with higher precision are used as priori-information, RAW-OBS-PPP needs about 8.67 min (mean value) in horizontal components, which is much faster than traditional LC PPP.