Characteristic Analysis of the Differences between TEC Values in GIM Grids

Abstract

Abstract. Using total electron content (TEC) from global ionosphere map (GIM) for ionospheric delay correction is a common method of eliminating ionospheric errors in satellite navigation and positioning. On this basis, the TEC of puncture point can be obtained by GIM grid TEC interpolation. However, in terms of grid, only few studies have analyzed the TEC value size characteristics of its four grid points, that is, the TEC difference characteristics among them. In view of this, by utilizing the GIM data from high solar activity years (2014) and low solar activity years (2021) provided by CODE, this paper proposes the grid TEC difference to analyze TEC variation characteristics within the grid, which is conducive to exploring and analyzing the variation characteristics of the ionosphere TEC in the single-station area. The results show that the TEC difference size within GIM grid is mainly related to the activity of ionosphere. The value is larger in high solar activity years and generally small in low solar activity years, and the value of high latitude area is always smaller than that of low latitude area. Specifically, in high solar activity years, most of the GIM grid TEC internal differences are within 4TECu in high and mid latitude regions, while only 78.17 % in low latitude regions; the grid TEC differences at 2-hour intervals are more scattered, and larger values occur in low latitude regions. In low solar activity years, the TEC difference values within GIM grid are mostly less than 2TECu, and most of them in the high and middle latitudes are within 1TECu. The GIM grid TEC difference values within 1-hour intervals are mostly less than 4TECu, and most of them in the high and middle latitudes are within 2TECu. The main finding of this analysis is that the grid TEC differences are small for most GIM grids, especially in the mid-high latitudes of low solar years. This means that relevant extraction methods and processes can be simplified when TEC within these GIM grids is needed.