Significant of Earth´s magnetic field and ionospheric horizontal gradient to GPS signals

Ray tracing technique can be used to determine the effect of Earth´s magnetic field to (Global Positioning Systems (GPS) signals with and without the presence of ionospheric horizontal gradient. In this project, Jones 3D Ray Tracing program was employed to study the effect of the ionosphere on GPS rays (L₁ and L2). The group path or delay is obtained from the difference between the distances of the ray path to the Earth station from the GPS satellite determined from the ray-tracing and the distance for propagation over the line of sight (LOS). Then, the residual range error (RRE), which is the difference between the standard dual frequencies models corrected range and LOS, will be calculated. The gradient ionospheric profile was then used to compare the effect of the ionosphere with and without gradient on GPS ray tracing. Results show that there is difference in between the RRE calculation with and without the presence of the ionospheric gradient. The Earth´s magnetic field effect to GPS signal is normally neglected since it has very minimal effect. However, in this research, results obtained show that the Earth´s magnetic field has to be taken into account in order to determine more accurate GPS ray tracing.