THE INFLUENCE OF ZENITH TROPOSPHERIC DELAY ON PPP-RTK

The PPP technique is more and more used in different GPS precise application. The PPP precision is related to many factors and the most important are: the number of satellites, the ambiguity resolution, the ability to model the ionospheric and tropospheric delays, solid earth and ocean tides, relativistic effects and antenna phase-center offsets and variations. The article is studying the effect of the zenith tropospheric delay (ZTD) using the GPT2 model and then computing in static mode the ZTD, which is than applied on PPP-RTK method. An analysis on dual frequency ionospheric-free phase combination (LC) and dual frequency ionospheric-free range combination (PC) was made in the first stage and then comparing the two solutions relative to the nominal position. The results revealed the fact that by using the ZTD determined in static mode in the detriment of ZTD from GPT2 model, the results are improving on North, East and Up position components. Also lower RMS was obtain when we used the ZTD from static mode comparative to the GPT2 model.