Assessment of Pseudorange Multipath at Continuous GPS Stations in Mexico

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 stud ied CGPS data from a large number of publicly available networks spanning Mexico. These include the RGNA (Na tional 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 Geo physics 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 continu ously 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 investi gated the sources of multipath, including changes associated with hardware replacement ( i.e. , receiver and antenna type) and receiver firmware upgrades.