Trazado de rayos para señales de satélites GPS: aproximación cuasi-longitudinal

Abstract

We present a ray tracing in the ionosphere for the signills emitted by GPS (Globill Positioning System) satellites in L band (Ll = 1575 MHz and L2 = 1228 MHz). The ionosphere may be considered as a medium with a spherical stratification and we assume a quasi-Iongitudinill propagation using the phase refractive index given by the Appleton-Hartree equation. We have used the quasi-parabolic model of electronic density for the computation of the length of group path. The parameters· for this model have been obtained from the Mark III ionospheric model; which has been elaborated at the University of Pennsylvania for different types of magnetic and solar activity. We obtain a precise villue for deviation of group path with respect to geometric path. Preliminary results show that the intervill of group ionospheric delays is between 30 ns to 50 ns for different elevation angles and the deviation due to refraction is 10 meters approximately. It is necessary to consider the curvature for the most accurate positioning.