Assessment of Pseudorange Multipath at Continuous GPS Stations in Mexico

G Esteban Vázquez,Joshua Spinler,Rick Bennett

doi:10.4236/pos.2013.43025

Abstract

We conducted a study to quantify the amount of pseudorange multipath at continuous Global Positioning System (CGPS) stations in the Mexican territory. These CGPS stations serve as reference stations enabling rapid high-precision three-dimensional positioning capabilities, supporting a number of commercial and public safety applications. We studied CGPS data from a large number of publicly available networks spanning Mexico. These include the RGNA (National Active Geodetic Network) administered by INEGI (National Institute of Statistics and Geography), the PBO network (Plate Boundary Observatory) funded by the National Science Foundation (NSF) and operated by UNAVCO (University NAVstar Consortium), the Southern California Integrated GPS Network (SCIGN), which is a collaboration effort of the United States Geological Survey (USGS), Scripps Institution of Oceanography and the Jet Propulsion Laboratory (JPL), the UNAM network, operated by the National Seismological System (SSN) and the Institute of Geophysics of the National Autonomous University of Mexico (UNAM), the Suominet Geodetic Network (SNG) and the CORS (Continuously Operating Reference Station) network, operated by the Federal Aviation Administration (FAA). We evaluated a total of 53 CGPS stations, where dual-frequency geodetic-grade receivers collected GPS data continuously during the period from 1994 to 2012. Despite carefully selected locations, all GPS stations are, to some extent, affected by the presence of signal multipath. For GPS network users that rely on pseudorange observables, the existence of pseudorange multipath could be a critical source of error depending on the time scale of the application. Thus, to identify the most and the least affected GPS stations, we analyzed the averaged daily root mean square pseudorange multipath variations (MP1-RMS and MP2-RMS) for all feasible satellites tracked by the CGPS networks. We investigated the sources of multipath, including changes associated with hardware replacement (i.e., receiver and antenna type) and receiver firmware upgrades.

Highlights

IntroductionAll GPS sites are affected to some extent by multipath effects, which arise when reflected GPS satellite signals reach the receiving antenna, interfering with and obscuring the direct signal used for precise positioning
continuous Global Positioning System (CGPS) sites from the RGNA, PBO, Southern California Integrated GPS Network (SCIGN), UNAM, Suominet Geodetic Network (SNG) and CORS networks considered in this study are located throughout the Mexican territory
At present the RGNA network consists of 23 continuous GPS stations administered by INEGI plus one cooperative station, which is controlled by the Institute of Land Information from Jalisco (IITJ)

Summary

Introduction

All GPS sites are affected to some extent by multipath effects, which arise when reflected GPS satellite signals reach the receiving antenna, interfering with and obscuring the direct signal used for precise positioning. The positioning solution of data derived from the repetition of the GPS satellite constellation between two sidereal days ought to be affected by “systematic” time-correlated multipath error This effect can be used to mitigate the multipath effect from the positioning time-series results [4,7,13] Reference [6] was the first to evaluate the pseudo-range multipath for a great number of CGPS stations from the CORS network, to closely identify problematic sites, and to compare various GPS hardware (i.e., receiver and antenna type) combinations. Pseud orange multipath estimates may serve as a source of environmental sensor data

GPS Instrumentation and Data Availability

Pseudorange Multipath Assessment

Results and Analysis

Conclusion