Comparison of GNSS ZTD estimates from relative and absolute processing solutions for climate applications
Abstract
The accuracy and homogeneity of Zenith Total Delay (ZTD) series estimated from ground-based GNSS data is strongly dependent on the data processing procedure (e.g. cutoff angle, elevation-dependent data weighting, mapping function and other details of the tropospheric model). Depending on the application targets (weather forecasting vs. climate monitoring), the requirements in terms of accuracy and homogeneity might be different. This study is intended to assess the impact of some GNSS data processing aspects not much investigated so far on the quality the derived ZTD series for climate applications.
We aim to answer the following scientific questions: 1) Does zero-differenced Precise Point Positioning (PPP) technique generate fewer outliers than relative double-difference (DD) processing? 2) What is the impact of orbit & clock products on the accuracy of ZTD estimates using the PPP technique? 3) What is the impact of ambiguity resolution on ZTD estimates in PPP solution? We analyzed results from more than 100 permanent stations using different strategies, options and software. We will present results from PPP and DD solutions processed with Bernese GNSS Software v.5.2 using different orbit and clock products, as well as PPP solutions using GIPSY-OASIS II with integer and float ambiguities. The solutions are inter-compared and compared to ERA-Interim reanalysis. The results indicate that PPP solutions have more ZTD estimates and fewer outliers than DD solution, mainly because there is no impact of gap at other stations of network. Moreover, compared to ERA-Interim, they have smaller biases and RMS errors and also higher correlation than DD solutions. Fixing phase ambiguities to integer values in PPP mode seems to have only a marginal impact on ZTD estimates, however the results seem to depend on the equipment (receiver and antenna) of the stations.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.G13D0562S
- Keywords:
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- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSESDE: 1218 Mass balance;
- GEODESY AND GRAVITYDE: 1220 Atmosphere monitoring with geodetic techniques;
- GEODESY AND GRAVITYDE: 1225 Global change from geodesy;
- GEODESY AND GRAVITY