Abstract
The Benchmark data set collected within the European COST Action ES1206 has aimed to support the development and validation of advanced Global Navigation Satellite System (GNSS) tropospheric products, in particular high-resolution zenith delays and tropospheric gradients. In this work we utilize this unique data set to show that the interpolation of GNSS Zenith Wet Delays (ZWDs) can be improved by utilizing tropospheric gradients. To do this we first prove the concept with simulated observations, that is, zenith delays and tropospheric gradients derived from a Numerical Weather Model. We show how tropospheric gradients can be converted to ZWD gradients. Then the ZWD gradients together with the ZWDs at selected reference stations are used in an inverse distance weighting interpolation scheme to estimate the ZWD at some target station. For a station configuration with an average station distance of 50 km in Germany and a period of two months (May and June 2013), we find an improvement of 20% in interpolated ZWDs when tropospheric gradients are taken into account. Next, we replace the simulated by real observations, that is, zenith delays and tropospheric gradients from a Precise Point Positioning (PPP) solution provided with the G-Nut/Tefnut analysis software. Here we find an improvement of 10% in interpolated ZWDs when tropospheric gradients are taken into account.
Highlights
Carrier phase observations from a ground-based Global Navigation Satellite System (GNSS) station allow the estimation of the Zenith Total Delay (ZTD) [1] and the tropospheric gradient [2]
We modelled GNSS observations according to the IERS 2010 conventions [18], and we used the file igs14_2013.ATX for deriving antenna phase center offsets and variations [19], which are consistent with the IGS2014 reference frame [20] used for precise satellite positions
We explain this reduction in the Root Mean Square Error (RMSE) of 5% instead of 10% by the fact that the GNSS ZTDs and tropospheric gradients are less accurate in RT than in post processing mode
Summary
Carrier phase (and code) observations from a ground-based Global Navigation Satellite System (GNSS) station allow the estimation of the Zenith Total Delay (ZTD) [1] and the tropospheric gradient [2]. From the ZTD, the Zenith Wet Delay (ZWD) can be retrieved. The tropospheric gradient at the station can be roughly related to the horizontal ZWD gradient at the station, that is, the partial derivative of the ZWD with respect to the longitude (latitude). A single station provides information on the ZWD and horizontal ZWD gradient. It is natural to try to improve ZWD interpolation by utilizing tropospheric gradients. The ZWD can be converted to the Integrated Water
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