Mapping the GPS multipath environment using the signal‐to‐noise ratio (SNR)

Abstract

[1] GPS multipath, where a signal arrives by more than one path, is a source of positioning error which cannot be easily neutralized. Better understanding of the multipath environment, i.e., the direction of and distance to reflecting objects, is important for multipath mitigation during the site construction phase as well as discerning the impact of multipath on positioning estimates for existing sites. This paper presents a tool called power spectral mapping that visually represents the multipath environment of a GPS site. This technique uses the spectral content (frequency and magnitude) of signal-to-noise ratio (SNR) time series to determine which satellites, and therefore which portions of the antenna environment, contribute significant multipath error and at what frequencies. Wavelet analysis is used to extract the time-varying frequency and magnitude content of various multipath constituents, and these data are projected onto a map representing the GPS antenna surroundings. Power spectral map examples from stations with very different multipath environments are presented. The maps are interpreted in terms of potential sources of multipath reflections, and how these multipath signals contribute to positioning error at each station is also assessed.Citation: Bilich, A., and K. M. Larson (2007), Mapping the GPS multipath environment using the signal-to-noise ratio (SNR),

Mapping GPS multipath: a case study for the lunar laser ranger timing antenna at HartRAO

“…Bilich and Larson (2007) indicated certain limitations associated with MP1 and MP2 derived from TEQC software to map multipath environments. One limitation is the use of Root Mean Square (RMS) error values to represent multipath.…”

GNSS multipath detection using three-frequency signal-to-noise measurements

“…One technique, known as power spectral mapping, uses the SNR measurements to map the multipath environment, giving an image of the reflective objects that have sent indirect signals to the receiver (Bilich and Larson 2008;Benton and Mitchell 2011). However, all of these techniques require post-processing of the data.…”

GPS multipath mitigation: a nonlinear regression approach

“…azimuth and elevation angles. Assuming that the satellite, antenna, and normal vector to the reflecting surface are all in a same plane, multipath reflections fall into two categories: forward-scatter and backscatter (Bilich and Larson 2007) as illustrated in Fig. 1.…”