Research On The Models And Methods Of Zenith Tropospheric Delay Correction Using Ground-based GNSS

Tropospheric delay correction error is the key factor in high-precision GNSSmeasurement, especially in GNSS elevation measurement. The empirical troposphericdelay models were difficult to satisfy the demand of high-precision GNSSmeasurement, besides, some models need the meterological parameters. Therefore, itis important to build an tropospheric correction model that unrelated to themeterological parameter or to refine the empirical models in some certains regionusing the regional CORS network data and the high-accuracy tropospheric delay ofIGS sites. This paper mainly focuses on the models and methods of the troposphericdelay correction using ground-based GNSS, the results are:1. The character of annual periodic, seasonal and the difference of the zenithtropospheric delay (ZTD) between the south hemisphere and north hemisphere areanalyzed using three years of the ZTD data obtained from20IGS sites that distributedin global area. The results show that the ZTD presents an obvious periodic andseasonal variation, and also the significant difference of the ZTD is presented betweenthe south hemisphere and north hemisphere.2. The ECMWF reanalysis products and the method of calculating the ZTD usingthe ERA-Interim data of ECMWF are introduced in detail, and also make anassessment for the calculated ZTD using ERA-Interim data over China region. Theresults show that the Inverse Distance Weighted method (IDW for short) presents aslight higher precision than other two methods when used to calculate the ZTD of IGSsite using ERA-Interim data, and also the bias and RMS of the calculated ZTD areless than2cm over China area, which have no obvious seasonal characters.3. The spatial characteristics of the ZTD is analyzed by combining the ZTD of IGSsite and the ZTD calculated from the ERA-Interim data. At last, the regional4Dzenith tropospheric correction model, EHBT model and EHT model are established,besides, the precision of the new models and its application are also analyzed usingthe measured data from Guangxi CORS network and Guangxi meteorological station,the results show: The new models with a higher precision used to estimate the ZTDwithin a certain condition, and also an good agreement can be achieved for the newmodels when used to derive the GPS-PWV, the RMS of GPS-PWV is better than2mm, comparing with the PWV that estimated by GAMIT.4. Five years of the ZTD data from2008to2012are observed from46IGS sites distributed in Asian area is regarded as reference valve that used to assess theaccuracy of ZTD calculated from EGNOS model. The Single-site Improved EGNOSmodel(named as SSIEGNOS model) over Asian is established using three years ofdaily bias of the ZTD calculated from the EGNOS model that analyzed by FastFourier transformation, and the accuracy and application of the EGNOS model andthe SSIEGNOS model are also analyzed in Asian area. The results show:(1) Relative to IGS observed ZTD, the bias and RMS for ZTD calculated from theEGNOS model are0.12cm and5.87cm respectively in Asian area, the bias and RMSare0.00cm and2.52cm respectively in China area;(2) The bias and RMS show a seasonal variation for the EGNOS model, while astable performance presented for the SSIEGNOS model, which shows a goodrectification for the EGNOS model in summer；(3) The relation between the bias and the altitude, longitude or latitude is notobvious for the two models, but the RMS decreases with the increasing altitude orlatitude;(4) The yearly bias and RMS show a significant improvement and stable for theSSIEGNOS model when used to predict the ZTD in Asian area...