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A vegetation index (VI) is a spectral imaging transformation of two or more image bands designed to enhance the contribution of vegetation properties and allow reliable spatial and temporal inter-comparisons of terrestrial photosynthetic activity and canopy structural variations.
The normalized difference vegetation index (NDVI) is a widely-used metric for quantifying the health and density of vegetation using sensor data. It is calculated from spectrometric data at two specific bands: red and near-infrared.
Vegetation indices classification is a system in which two or more spectral bands are combined through defined statistical algorithms to reflect the spatial properties of a vegetation cover. Most of these indices make use of the relationship between red and near-infrared (NIR) bands of satellite images to generate vegetation properties. Several ...
The enhanced vegetation index (EVI) is an 'optimized' vegetation index designed to enhance the vegetation signal with improved sensitivity in high biomass regions and improved vegetation monitoring through a de-coupling of the canopy background signal and a reduction in atmosphere influences.
The definition of a specific vegetation type may include not only physiognomy but also floristic and habitat aspects. [ 15 ] [ 16 ] Furthermore, the phytosociological approach in the study of vegetation relies upon a fundamental unit, the plant association , which is defined upon flora.
The index is given as: = (+) (+ +) where L is a canopy background adjustment factor. An L value of 0.5 in reflectance space was found to minimize soil brightness variations and eliminate the need for additional calibration for different soils. The transformation was found to nearly eliminate soil-induced variations in vegetation indices. [1]
The system has been shown to fit not just tropical vegetation zones, but Mediterranean zones, and boreal zones too, but is less applicable to cold oceanic or cold arid climates where moisture becomes the predominant factor. The system has found a major use in assessing the potential changes in natural vegetation patterns due to global warming. [3]
Tasseled Cap Band 2 (greenness, a measured value for the vegetation) Tasseled Cap Band 3 (wetness, a measured value for interactions of soil and canopy moisture) The algorithm for these three levels of information is a weighted sum of the Landsat bands (without the thermal channel 6), where each band is multiplied by the specific coefficients ...