Estimation of GPS Tropospheric delays using different data processing strategies in Iran

Abstract

In this study, the performance of different processing software and strategies on the estimation of Zenith Wet Delay (ZWD) from Iran Permanent GPS Network (IPGN) was evaluated. For this purpose, GAMIT (version 10.4) and Bernese (version 5.0) software were used to estimate the ZWD values in baseline and Precise Point Positioning (PPP) mode, respectively. Then, the GPS ZWD time series in Tehran, which is the only International GNSS Service (IGS) station in Iran, were validated with the corresponding values derived from the measurements of the nearby radiosonde site at Mehrabad airport. Based on one year of estimates in both network (or baseline) and PPP mode, the GPS and radiosonde ZWD were consistent with a mean bias of 6 mm and standard deviation of 12 mm. furthermore, the IGS final tropospheric products over 2011 were used to validate our GPS data processing in this study. The Results showed that there is a good agreement between our estimates and those obtained from IGS with a mean bias of less than 1 mm. Comparing PPP with the network GPS ZWD solutions in 15 stations of IPGN over one year, showed that two methods are consistent with mean bias and standard deviation of less than 2 and 5 mm. Finally, to examine the operational usage of IPGN tropospheric products, using the IGS ultra-rapid orbits the near real time ZTD were estimated and compared with final post processed solutions. For all stations, the near real time ZTD estimation results were comparable with the corresponding post processed estimates in terms of bias and standard deviation. The obtained correlation coefficient between final and near real time solutions was more than 0.95. These results suggest that ZTD derived from Iranian regional GPS network has the potential to incorporate in different meteorological applications.

Tropospheric delay efficiency from CSRS-PPP online service for meteorologists in Iran

“…Additional information such as the type of observations, the model and height of the antenna, and the initial coordinates of the receiver used to determine the exact absolute position are extracted and used from the observation file by the CSRS-PPP software. Khaniani and Ghahremani, in 2018, showed that the tropospheric estimates obtained from the GAMIT software using differential processing mode are in high agreement with the corresponding estimates obtained from the IGS site processes at the Tehran station [26]. Here, the GAMIT software is used to process station networks, and these values are considered reliable values to evaluate the ZTD values obtained from the PPP online service.…”