GPS Landing System Multipath Evaluation Techniques and Results

Abstract

A Special Category I system (SLS 2000) has been completed and certified to RTCA DO–217 standards. Substantial amounts of multipath data have been collected at various installation sites. This paper describes the techniques used to characterize the multipath environment, the multipath models developed based on collected data and results from SCAT I installations and prototype LAAS test sites. The characterization of multipath involves determining the multipath 1–sigma error as a function of elevation, the spectral content, the Gaussian properties and the occurrence of fading. In terms of modelling, the paper discusses the relation between Doppler differences and spectral content, the impact of smoothing and methods for handling non Gaussian distributions. Statistical multipath data from 2 or 3 ground receivers collected over 24 hours and observed differences in the environment at different installation sites as well as observed events of particular interest are included in the paper.