GLOBALINĖS PADĖTIES SISTEMOS PALYDOVŲ SIGNALŲ VĖLAVIMAS DĖL JONOSFEROS POVEIKIO

Abstract

Summary GPS signals are transmitted through the atmosphere from a satellite to a receiver. The atmosphere could be divided into different layers, according to their physical characteristics and their influence on radio waves propagation. Ionosphere is a disperse medium for radio waves and propagation velocity depends on the frequency of GPS signals. It can have many effects on GPS, but here the author pays attention to ionospheric delay only. It is critical for single frequency GPS receivers, while two frequencies GPS receivers' user can almost completely eliminate the effect of the ionospheric delay. Free electrons in the ionosphere produce most of the effects on the GPS signal modulation. The delay is proportional to the integrated number of free electrons along the transmission path and inversely proportional to the square of the transmission frequency. Typical zenith delays range from a few meters to a maximum of 15 meters. Of course, delays could reach even 100 meters at low elevation angles. There a...