Application of 3-D Ray-Tracing for Accurate GPS Range Finding

Ionospheric error affects the accuracy of global positioning system (GPS). This paper studies the ionospheric error on transionospheric signal propagation from satellite to ground paths using readily available GPS satellites utilizing Jones 3-D ray-tracing. The ionospheric delay or advance is obtained from the difference between the distance of the ray path to the receiver from the satellite determined from the ray-tracing and the distance for propagation over the line of sight (LOS) at the velocity of light in vacuum. The residual range error (RRE), that is the difference between the standard dual frequency models corrected range and LOS, is calculated. Results show that the RRE of group value is different from RRE of phase advance. The higher order term in total electron content (TEC) calculation that relates to the refractive index is normally neglected due to its small value, but the results of ray-tracing clearly show that it does have some effects. These results should be considered for accurate GPS range finding.