Validation of real-time zenith tropospheric delay estimation with TOMION software within WAGNSS networks
Tutor / director / evaluatorHernández Pajares, Manuel
Document typeMaster thesis
Rights accessOpen Access
The TOmographic Model of the IONospheric electron content (TOMION) software implements a simultaneous precise geodetic and ionospheric modeling, which can be used to test new approaches for real-time precise GNSS modeling (positioning, ionospheric and tropospheric delays, clock errors, among others). In this work, the software is used to estimate the Zenith Tropospheric Delay (ZTD) emulating real time and its performance is evaluated through a comparative analysis with a built-in GIPSY estimation and IGS final troposphere product, exemplified in a two-day experiment performed in East Australia. In addition, the troposphere mapping function was upgraded from Niell to Vienna approach. On a first scenario, only forward processing was activated and the coordinates of the Wide Area GNSS network (relative) were loosely constrained, without fixing the carrier phase ambiguities, for both reference and rover receivers and the ionospheric modeling was turned off. On a second one, precise point positioning (PPP) was implemented, every 900 seconds, introducing IGS transmitted orbits and clocks. Comparisons between TOMION and GIPSY estimates and IGS final product have been performed and the agreement between the the first two ones was of +/-5mm, while both were over 2cm biased with respect to IGS products, despite using IGS satellite clocks and orbits for TOMION computations. Moreover, the standard deviation of the TOMIONs estimates computed in PPP mode was between 3 and 13mm, when compared to both external references. Additionally, Vienna mapping function showed in general a fairly better agreement than Niell although further improvement could be achieved for such estimations with coefficients for the Vienna mapping function calculated from raytracing as well as integrating meteorological comparative parameters.