Effect of altitude and distance on zenith tropospheric delay and integrated water vapour estimations in a local GNSS CORS network

In this paper, to investigate the usability of Continuously Operating Reference Stations managed by the Istanbul Water and Sewerage Administration (ISKI CORS) for weather prediction studies, the effects of altitude and distance on Zenith Tropospheric Delay (ZTD) and Integrated Water Vapour (IWV) estimations were analysed. Within the scope of this study, the authors determined accuracies of ZTD and IWV values based on the selected reference stations and analysed them for altitude and distance factors. GnSmart software is used for ZTD estimation as this software broadcasts CORS correction and GNSS Analysis and Positioning Software (GAPS) is used for IWV estimation. In this study, a single reference station was used to test the accuracy of ZTD and IWV values obtained from local ISKI CORS network stations (TUZL station for ZTD values and radiosonde station numbered 17064 for IWV values). The determined RMSE values could not reach the ZTD and IWV precision standards of the World Meteorology Organization (WMO). One reason for this is that a single station is selected as a reference. In short, the authors express that the ZTD and IWV values of ISKI CORS stations are not similar, but there is a significant difference between them. It was also understood that a single radiosonde station is not sufficient to determine the IWV values of the stations in the local ISKI CORS network, and the GNSS IWV values obtained from the stations can be meaningful.