Wavelet analysis for quantifying NavIC-IR multipath signal frequency with the aim of determining soil moisture in agricultural fields

Abstract

ABSTRACTThis paper explores the potential of Global Navigation Satellite Systems (GNSS) multipath signals for soil moisture retrieval, specifically focusing on Navigation with Indian Constellations (NavIC). Utilizing GNSS-Interferometric Reflectometry (IR) techniques, wavelet analysis is employed to extract the low-frequency signal sensitive to soil moisture from the reflected multipath signals. The reconstructed low-frequency multipath signal is then subjected to Lomb-Scargle Periodogram (LSP) analysis to determine multipath frequency. A comprehensive sensitivity analysis reveals the dependency of multipath frequency on field soil moisture, particularly in the presence of vegetation. The sensitivity varies across different crop growth stages, categorized by crop height. The Pearson correlation coefficient (r) for crop height less than one wavelength was 0.81 and for greater than one wavelength it was 0.67. The sensitivity of multipath frequency for soil moisture was 0.48 rad s−1 cm3 cm−3 and 0.47 rad s−1 cm3 cm−3 for crop height less than one wavelength and crop height greater than one wavelength respectively.This research underscores the potential of GNSS-IR techniques, incorporating wavelet analysis and LSP, for soil moisture sensitivity, especially in areas with varying vegetation and crop growth stages.