Ambiguity resolution of phase measurements is implemented for Precise Point Positioning (PPP) in global navigation satellite systems (GNSS). Underlying feature of design matrix in singular system of GNSS equations that allows to estimate user coordinates with ambiguity resolution is revealed. Algebraic details of rank deficiency overcoming are considered. Observation models on GPS and GLONASS initial frequencies are proposed and investigated. Filtration method allowing to exclude influence of ionosphere delays to user coordinates is described. Significant reduction of convergence period for PPP due to ambiguity resolution is shown. Comparison of user positioning quality with use of decoupled satellite clocks from global and local networks is presented.

Keywords: GNSS, PPP, float PPP, integer PPP, ambiguity resolution, decoupled clocks, excluding Kalman filter.