Investigating Effects of Usage of Zenith Tropospheric Wet Delay Models on Positioning Accuracy

Gürtürk M., Erdem Ç., Soycan M.

INTERNATIONAL SYMPOSIUM ON GIS APPLICATIONS IN GEOGRAPHY & GEOSCIENCES, Çanakkale, Turkey, 18 October 2017 - 21 August 2019, pp.117

  • Publication Type: Conference Paper / Summary Text
  • City: Çanakkale
  • Country: Turkey
  • Page Numbers: pp.117
  • Yıldız Technical University Affiliated: Yes


Global Navigation Satellite System (GNSS) is actively being used for various purposes such as engineering studies, deformation measurements, meteorological predictions, navigation. The method would be used depends on work to be applied. Relative and absolute positioning techniques are the two main methods that distinguish positioning with GNSS as the working methodology. Precise Point Positioning (PPP) which is an absolute positioning technique has stood out among these techniques in recent years and is becoming more popular, has become an important alternative to relative positioning technique in evaluating GNSS data (postprocessing) in terms of position accuracy it provides. This improvement in accuracy relies on modelling of the errors in post-process phase. There are many error sources those have an effect on positioning accuracy. Atmospheric error sources are ionospheric delay and tropospheric delay. While ionospheric delay error can be eliminated with using L1-L2 phase and also code observation differences, tropospheric delay needs to be modelled because it is not predictable due to constantly changing water vapour in the layer. In this study, 3 IGS station couples those have horizontal distance less than 160 km from each other with significant height difference were selected. Coordinates were obtained for 7 days from Scripps Orbit and Permanent Array Center (SOPAC) to perform repeatability analysis. At first, these datas were processed in GIPSY-OASIS 6.4 (GNSS-Inferred Positioning System and Orbit Analysis Simulation Software) with Kinematic PPP approach using 5 minutes intervals while Zenith Tropospheric Wet Delay (ZWD) modelling on, and then secondly off. The results were compared to absolute position of the sites to determine effects of ZWD modelling on coordinate values as in RMS values. The purpose of the study was to see if there was a correlation between height difference and RMS improvement with usage of ZWD modelling.