Precise Point Positioning Improvement Using Ray Tracing and Numerical Weather Models

During last two decades Precise Point Positioning has been considered as one of the most important methods in satellite geodesy. Despite the efforts to improve the PPP precision, this method has not yet achieved the precision of Relative positioning methods. Most of the efforts on PPP improvement focus on the processing models and phase ambiguity. Modeling the tropospheric delay is very crucial to achieve high precision in Precise Point Positioning. There are different methods to estimate this delay such as ray-tracing or using appropriate mapping functions e.g. GMF, VMF,, …, which relate the zenith path delay to slant path delay.In this paper, the ray-tracing slant path delay has been used as a reference value. Then three other delays are calculated using zenith path delay obtained from PPP and Global mapping function in different ways. The difference between the delay computed by ray-tracing method and those three other delays is applied to the RINEX observation files. The new RINEX files are implemented for PPP reprocessing. Comparing the achieved results, with the ITRF coordinates of points, shows that applying the difference of slant path delay from ray-tracing and slant path delay which is computed by zenith path delay of PPP (using 88% of hydrostatic global mapping function and 12% of non-hydrostatic global mapping function) to the RINEX files, improve positioning accuracy.