Modeling GPS phase multipath with SNR: Case study from the Salar de Uyuni, Boliva

Abstract

[1] Multipath, wherein a signal arrives at the receiving antenna by more than one path, is a significant and largely unmodeled source of GPS positioning error. We present a technique for mitigating specular multipath in GPS carrier phase measurements using the signal-to-noise ratio (SNR), in which the frequency and amplitude content of non-stationary oscillations in SNR are modeled to extract multipath parameters (direct and reflected signal amplitudes, and the phase difference between direct and indirect signals). The frequency content of SNR data is estimated using wavelet analysis, then used to initialize an adaptive least squares process to solve for time-varying multipath parameters. Multipath corrections derived from these parameters are applied to the phase observables. We demonstrate this technique using campaign GPS data collected over a large salt flat (Salar de Uyuni), specifically a tripod-mounted station which experienced long-period (300-2000 s) multipath oscillations in SNR from ground reflections. By contrasting position solutions before and after applying multipath corrections, we demonstrate a reduction in carrier phase postfit residual RMS of up to 20% for static positioning, and 1-7 dB reduction in spectral power at multipath periods for kinematic positions.

Considering Inter-Frequency Clock Bias for BDS Triple-Frequency Precise Point Positioning

“…The GPS multipath, which can be extracted using the ionospheric-free geometric linear combination, is a function of satellite elevation angle and antenna height, etc. [25][26][27]. The multipath effects should be considered during the IFCB estimation with the use of DIF measurements consisting of two different ionospheric-free carrier phase combinations.…”

“…Since the physical surface formation surrounding the ground station receivers used in this paper does not change during a certain time span, the impact of variability of receiver's antenna height should not be considered. Bilich et al [27] illustrated the elevation angle dependence of phase multipath error. The satellite signals with low elevation angles exhibit large multipath, especially for those below 35 • elevation.…”

GNSS Positioning in Non-line-of-Sight Context—a Survey for Technological Innovation

“…Based on a user-defined threshold in this domain, the potential NLOS signals are either excluded or tagged in order to apply a weighting. Implementations of this can be found in [31], [32], [33], [34], [35], [36] and [37].…”

“…Thus, building boundary data, digital terrain models and building models were used. [8], [14], [33], [50], [80], [98], [99] [4], [14], [30], [33], [35], [92], [47], [48], [50], [51], [58], [67], [68], [70], [74], [81], [82], [83], [85] Via person [18], [22] [43], [49], [66], [71] (No information) [28], [29], [31], [32], [34], [37], [73], [84], [86], [87], [88] Simulation Static measurement…”

Deriving surface soil moisture from reflected GNSS signal observations from a grassland site in southwestern France

“…The GNSS-IR technique allows relating the reflected signal to the characteristics of the reflecting surface and to retrieve geophysical variables. Over land, variables such as soil moisture, snow depth and vegetation parameters can be observed using this technique (Larson et al, 2008;Small et al, 2010;Larson and Nievinski, 2013;Wan et al, 2015;Larson, 2016;Roussel et al, 2016;Zhang et al, 2017). GNSS satellites emit active Lband microwave signals (between 1.2 and 1.6 GHz).…”