The ionosphere is one of several layers of the Earth’s atmosphere. The influence of the ionosphere on GPS positioning is one of the largest error sources. It is generally modeled in a global scale by determining its Total Electron Content (TEC) in the signal path using all available world wide GPS observations to be used in GPS processing procedure to overcome its error, the modeled product is known as Global Ionospheric Model (GIM). In this research, a Local Ionosphere Model (LIM) was created using Bernese software, by the computation of TEC in a local area. This process was based on the single layer model to determine the appropriate TEC values by using the Egyptian coastal part composed of five stations of the network made by the Egyptian National Research Institute of Astronomy and Geophysics (ENRIAG) at (2001). The influence of using the global ionospheric model versus the obtained local model was investigated, with precise ephemeris, for different base line lengths, and different observational sessions (1, 2, 3, 4, 5 and 6 hours), based on the commercial software Trimble Total Control (TTC). Additionally, the influence of the Precise Ephemeris (PE) alone without using ionospheric models was also studied for the same base line lengths, and the same observation sessions based on the same commercial software. The results indicate that the mean of vector length errors was improved when using the (LIM) with precise ephemeris, at all different baseline lengths and also with different observational sessions. |
