Comparing Accuracy of Different Atmospheric Mapping Functions using Continuous GPS Data in Iran

One of the error sources in GPS observations is tropospheric delay. Unlike the ionospheric delay, it is not possible to eliminate tropospheric delay from observations by using dual-frequency receivers and we have to estimate it or to use local or global tropospheric models such as Saastamoinen, Hopfield , etc. Some functions called Atmospheric Mapping Functions are used for these models. Different mapping functions for both hydrostatic and wet tropospheric components have been presented by researchers in this field. In the present study, by using GPS data of permanent station in Tabriz for 2012, we have tried to do a comparison different mapping functions of Saastamoinen, Hopfield, Davis, Chao, B&E and Neil. In this test, we estimated the coordinates of the station as well as the tropospheric delay including hydrostatic and wet components in different weather conditions and Zenith angles of 1̊-60̊ .
The results show that Niell mapping function may have the same behavior relative to other functions to estimate zenith tropospheric delay (ZTD) in different weather conditions and slant tropospheric delay (STD) under the zenith angles smaller than 30̊. But Niell mapping function provides a better estimation of zenith tropospheric delay and slant tropospheric delay under zenith angles between 30̊-60̊ with the lowest RMST. Moreover, according to the fixed coordinates of GPS station (Tabriz), the estimated coordinate components by Niell mapping function have totally the minimum difference.