The pseudo-range error due to multipath effects in the GPS system is studied.First the time de lay of specular multipath aignals and its freqency bandwidth spread are analyzed.Then an extensive study is car ried out for the influence of multipath signals to the S-curves and the peudo-range errors when tracking the PN code signals with coherent and noncoherent delay lock loops.Moreover
several methods for reducing multipath er rors are proposed.