GPS Multipath Analysis Using Fresnel Zones

Abstract

GNSS (Global Navigation Satellite Systems) multipath has been subject to scientific research for decades and although numerous methods and techniques have already been developed to mitigate this effect, it is still one of the accuracy-limiting factors in many GNSS applications. Since multipath is highly dependent on the individual antenna environment, there is still a need for new methods and further investigations to increase the understanding of this systematic effect. In this paper, the concept of Fresnel zones is applied to two different aspects of multipath. First, Fresnel zones are determined for the line-of-sight transmission between satellite and receiver. By comparing the boundary of the Fresnel zones to an obstruction adaptive elevation mask, potentially diffracted signals can be identified and excluded from the position estimation process. Both the percentage of epochs with fixed ambiguities and the positioning accuracy can be increased by the proposed method. Second, Fresnel zones are used to analyze the multipath induced by a horizontal and spatially-limited reflector. The comparison of simulated and real signal-to-noise (SNR) observations reveals a relationship between the percentage of the overlap of the Fresnel zone and reflector and the occurrence of multipath. It is found that an overlap of 50% is sufficient to induce multipath effects. This is of special interest, since this does not confirm theoretical assumptions of the multipath theory.

Improved urban navigation with shadow matching and specular matching

“…Specifically, we assume that a receiver is likely to track a reflected signal if a large percentage (50%) of the first Fresnel zone is both visible to the receiver and overlaps with the reflecting surface. The 50% threshold has been shown to be a sufficient metric in other applications for predicting surface reflections (Zimmermann, Schmitz, Klingbeil, & Kuhlmann, 2019). The algorithm for determining the specularity metric for each direction in the sky is summarized in Algorithm 1 and illustrated in Figure 9.…”

Intense L-Band Solar Radio Bursts Detection Based on GNSS Carrier-To-Noise Ratio Decrease over Multi-Satellite and Multi-Station

“…It is extremely important to keep this system free of interference. Types of interference with GNSS include multipath [ 3 , 4 ], ionospheric scintillation [ 5 ], spoofing [ 6 , 7 ], electromagnetic interference, satellite signal anomalies, and intense L-band solar radio bursts (SRBs) [ 8 ]. SRB is a strong signal in the microwave band from solar plasma radiation and cyclotron synchrotron radiation.…”

Intrinsic Identification and Mitigation of Multipath for Enhanced GNSS Positioning

“…Since there are different ways to select mother wavelets, it is hard to justify the best one to be used for decomposition and reconfiguration. Similar to the wavelet transform, some filtering approaches—such as the short-time frequency transform (STFT) [ 18 ], Vondrak filter [ 19 ], adaptive filter [ 20 ], and some other methods [ 21 , 22 , 23 , 24 , 25 ]—are also discussed to deal with multipath mitigation. From the abovementioned research items, the filtering results are usually sensitive to selection of control parameters and filter thresholds.…”