GNSS-IR applied to vineyard moisture

Multipath is one of the most severe station-dependent error sources in static GNSS positioning, yet it can be used to conduct several studies. The Global Navigation Satellite System – interferometry and reflectometry (GNSS-IR) technique has been widely used to study soil moisture and snow depth. In this work, GNSS-IR is used to find the correlation between vineyard leaf moisture and GNSS signal-to-noise ratio (SNR). The GNSS data have been collected during the leafy period in a vineyard when water content varies significantly. Only data from low satellite elevation angles (between 5º and 30º) have been taken into consideration and the azimuth has been studied because trellis plantation was used in the vineyard. The amplitudes of the SNR data correlate with the water content in vineyard leaves. Both GPS and Galileo signals were evaluated, but a lack of signals prevented full use of the Galileo system. Our study shows that the L2C signal is better for the analysis of humidity as there is a greater correlation. Finally, the results show that with the latest GPS, L2C, and L5 signals, the SNR can be used more reliably for multipath reflectometry. GPS L5 signal will become more important because of the increasing compatibility and interoperability of global satellite navigation systems.