Vegetation indices use data gathered by satellite sensors that measure wavelengths of light absorbed and reflected by green plants. Certain pigments in plant leaves strongly absorb wavelengths of visible (red) light. The leaves themselves strongly reflect wavelengths of near-infrared light, which is invisible to human eyes.
Many sensors carried aboard satellites measure red and near-infrared light waves reflected by land surfaces. Using mathematical formulas (algorithms), scientists transform raw satellite data about these light waves into vegetation indices. A vegetation index is an indicator that describes the greenness — the relative density and health of vegetation — for each picture element, or pixel, in a satellite image.
A number of vegetation indices of various degrees of sophistication have been developed to measure vegetation condition and density and to correct for illumination and atmospheric conditions. Examples of some of the most widely used vegetation indices are: EVI, NDVI, SAVI, NDWI among others.
By dividing NIR/Red reflectance, VI and LAI characterise their relationship and use this information to evaluate vegetation type, condition and density.
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I am a Database Assistant, supporting the tropical forest database ForestPlots.net and associated research projects RAINFOR, Afritron and T-FORCES. I am studying for a Masters in GIS alongside my research...
My long-term research goal is to understand the dynamics of carbon and biodiversity across the world’s tropical forests, how these change with our changing climate, and how they may feedback...