Effects of different mapping functions on GPS network solutions

In geodetic studies, Global Positioning System (GPS) is widely preferred since it can be operated day and night and in all weather conditions. Also, GPS is used especially in the studies which require high accuracy such as monitoring deformations and determining tectonic movements. However, GPS error sources must be eliminated to achieve precise positioning. The troposphere, one of the major error sources, causes signal delays due to its dry air and water vapor content. Due to the fact that composition of the troposphere changes heavily both temporally and spatially, tropospheric delay is determined in zenith direction although it occurs along the signal path. This relation between the zenith direction and signal path is provided by the mapping functions (MFs). For the tropospheric delays the zenith signal delays are mapped to satellites at a given ground-based stations using MFs. In this study, the effects of most preferred MFs in the literature such as the Niell Mapping Function, the Global Mapping Function and the Vienna Mapping Function 1 have been investigated to show their effects on GPS network solution. Three GPS networks that have different baseline lengths have been analyzed. According to the results, it can be stated that the differences between the MFs are negligible, especially in the horizontal component. Moreover, since the vertical coordinate differences are greater in the network that has largest baselines, the choice of MF can significantly affect the results of the studies which require larger baselines.