Monitoring Vegetation Optical Depth (VOD) using GNSS transmissiometry at the Vielsalm ICOS site

Monitoring vegetation water dynamics is essential to better understand ecosystem functioning and resilience under changing climate conditions. Vegetation Optical Depth (VOD), derived from microwave signals, has emerged as a valuable proxy for vegetation water content and biomass. In this poster, we present in situ measurements of VOD acquired using the GNSS-Transmissometry (GNSS-T) technique at the ICOS forest site of Vielsalm (Belgium). A dedicated station was installed on 11 March 2025 to continuously record the attenuation of GNSS signals as they pass through the forest canopy, providing a direct estimate of VOD at high temporal resolution.
The station records data every 15 seconds, providing high temporal resolution observations that enable detailed monitoring of vegetation dynamics. The dataset allows tracking short-term variations and has the potential to capture seasonal changes, the impact of droughts, and other environmental influences on vegetation. These ground-based VOD observations provide an independent reference for validating satellite-derived VOD products and improving vegetation model parametrization.
This work demonstrates the potential of GNSS-T for long-term vegetation monitoring in temperate forests and contributes to bridging the gap between ground measurements, remote sensing, and ecosystem modelling.