Detection of GNSS antenna oscillatory motion and multipath conditions via exploitation of multipath-induced SNR variations

Abstract

The multipath effect is well known as one of the dominant error sources in most high-precision GNSS applications, as its site-dependent and fast-changing nature render it challenging to model and mitigate using differencing techniques. However, in this study, we present a novel approach of using the multipath effect of GNSS signal in the case of oscillatory motion of a GNSS antenna to determine the characteristics of the oscillatory motion by utilizing the signal-to-noise (SNR) ratio measurements of the GNSS signals and without applying the positioning solution or the use of other sensors. The proposed method is based on the hypothesis that for a short time period, while the multipath conditions remain constant and the satellites are approximately at the same position, an oscillation-type motion of the antenna should generate changes in multipath, expressed as oscillatory pattern variations in the SNR measurements of the satellites. This approach can be used to identify the multipath parameters and extract characteristics of the oscillatory motion of the GNSS antenna. The SNR-based modeling of cm-level antenna oscillations was demonstrated in simulated and field experiments. The benefits of this method include immunity to poor satellite constellation geometry, adaptability to changing multipath geometry and fast processing time. This approach could potentially, under conditions, contribute to GNSS reflectometry (GNSS-R) applications, where the oscillatory motion of the GNSS antenna generates the same effect as the satellite motion-induced multipath, limiting simultaneously the observation periods and the amount of data to be processed.