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NDVI in agriculture

Using maps of vegetation indices created based on space images.

It is known that the crop canopy reflection in red and near-infrared zones of the electromagnetic spectrum depends on its green phytomass. Normalized Difference Vegetation Index (NDVI) is widely used to quantify the vegetation condition. NDVI can also describe the vegetation density, allowing the farmers to evaluate plant germination, growth and productivity. The index is calculated as the reflection difference in the near-infrared and red spectrum divided by its total. As a result the NDVI values range from -1 to 1. For the green vegetation the red spectrum reflection is always lower than in the near-infrared due to light absorption by chlorophyll. Therefore NDVI values for the vegetation can not be lower than 0.

Object type Reflectance * in the red spectrum Reflectance in the near-infrared spectrum NDVI value
Dense vegetation
0.1
0.5
0.7
Scarce vegetation
0.1
0.3
0.5
Bare soil
0.25
0.3
0.025
Clouds
0.25
0.25
0
Snow and ice
0.375
0.35
-0.05
Water
0.02
0.01
-0.25
Artificial materials (concrete, asphalt)
0.3
0. 1
-0.5

* Indicates the portion of light reflected by the object. Scale range from 0 to 1.

Index calculation for each space image pixel in red and near-infrared spectrum allows obtaining a derived image – the NDVI map.

(Source – http://scanex.ru/en/monitoring/default.asp?submenu=farming&id=ndvi)

NDVI in agriculture обновлено: July 15, 2014 автором: admin

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