Radar Vegetation Index (RVI)
The Radar Vegetation Index (RVI) is a remote sensing metric used to estimate vegetation cover and biomass. It is derived from radar (synthetic aperture radar or SAR) data, specifically from the polarization channels. Unlike traditional vegetation indices like the Normalized Difference Vegetation Index (NDVI), which rely on optical data from visible and near-infrared (NIR) light, the RVI takes advantage of the radar’s ability to penetrate through clouds and operate in various weather conditions.
Formula:
The RVI is typically calculated using quad-polarization SAR data, and its formula can be expressed as:
Where:
- σ_HH: Backscatter coefficient for horizontally transmitted and horizontally received signals.
- σ_VV: Backscatter coefficient for vertically transmitted and vertically received signals.
- σ_HV: Backscatter coefficient for horizontally transmitted and vertically received signals.
Interpretation:
- Low RVI values: Suggest bare soil or very low vegetation.
- High RVI values: Indicate dense vegetation or forests.
Benefits of RVI:
- All-weather capability: Radar can collect data under cloudy or rainy conditions, unlike optical sensors.
- Penetration: Radar can penetrate the canopy and provide information about vegetation structure.
- Sensitivity to biomass: It is particularly useful for estimating biomass in agricultural or forested areas.
RVI is widely used in agriculture, forestry, and environmental monitoring. It helps to track vegetation health, growth stages, and biomass estimation.
