Retrieving of GNSS Tropospheric Delays from RTKLIB in Real-Time and Post-processing Mode

Abstract

Global Navigation Satellite Systems (GNSS) allow a precise estimation of atmospheric water vapour what is successfully used in weather forecasting, namely in Numerical Weather Prediction (NWP) models. In this study the quality of real-time and post-processed zenith total delay (ZTD) values from GPS (Global Positioning System) Precise Point Positioning (PPP) technique processing is investigated. GPS observations from a month-long period and eight European stations were processed in RTKLIB program package. Two versions of real-time processing solutions using different real-time IGS (International Global Navigation Satellite Systems Service) products (IGS01, IGS03) and two versions of post-processed solutions using different strategies were evaluated. Obtained ZTDs were compared with the final IGS ZTD product. The mean RMSE (root-mean-square error) was 10.3 mm for real-time solution based on the IGS03 real-time product and 12.2 mm for the other solution based on the IGS01 product. Both post-processed solutions reached a mean RMSE of about 5 mm. The better real-time ZTD solution from RTKLIB using IGS03 product was therefore close to the 10 mm value defined as a target ZTD accuracy necessary for their usage in NWP models and nowcasting applications in meteorology.