The normalized difference vegetation index (NDVI) is a simple graphical indicator that can be used to analyze remote sensing measurements and assess whether the target being observed contains live green vegetation or not.
A Normalized Difference Vegetation Index (NDVI) is an equation that takes into account the amount of infrared reflected by plants. Live green plants absorb solar radiation, which they use as a source of energy in the process of photosynthesis. The reason NDVI is related to vegetation is that healthy vegetation reflects very well in the near-infrared part of the electromagnetic spectrum. Green leaves have a reflectance of 20% or less in the 0.5 to 0.7 micron range (green to red) and about 60% in the 0.7 to 1.3 micron range (near-infrared). Overview. The Normalized Difference Vegetation Index (NDVI) data set is available on a 16 day basis for the six year period between 2001 and 2006. The product is derived from bands 1 and 2 of the MODerate-resolution Imaging Spectroradiometer on board NASA's Terra satellite. The Normalized Difference Vegetation Index (NDVI) data set is available on a 16 day basis for the six year period between 2001 and 2006 This difference in absorption is quite unique to live vegetation and provides a measure of the greenness of the vegetation. NDVI is an index which measures this difference, providing a measure of vegetation density and condition. It is influenced by the fractional cover of the ground by vegetation, the vegetation density and the vegetation greenness. It indicates the photosynthetic capacity of the land surface cover.  The normalized difference vegetation index (NDVI) is a simple graphical indicator that can be used to analyze remote sensing measurements, typically but not necessarily from a space platform, and assess whether the target being observed contains live green vegetation or not. Contents.  NDVI, the Foundation for Remote Sensing Phenology. Remote sensing phenology studies 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. Normalized Difference Vegetation Index (NDVI) is calculated from the visible and near-infrared light reflected by vegetation. Healthy vegetation (left) absorbs most of the visible light that hits it, and reflects a large portion of the near-infrared light. The NDVI is an index calculated based on the radiation of remote sensing reflection bands: NIR and RED are the reflectance of the near-infrared and red bands; in the particular case of Landsat images, it corresponds to bands 4 and 3. The most common measurement is called the Normalized Difference Vegetation Index (NDVI). Very low values of NDVI (0.1 and below) correspond to barren areas of rock, sand, or snow. Moderate values represent shrub and grassland (0.2 to 0.3), while high values indicate temperate and tropical rainforests (0.6 to 0.8).  Nearly all satellite Vegetation Indices employ this difference formula to quantify the density of plant growth on the Earth  near-infrared radiation minus visible radiation divided by near-infrared radiation plus visible radiation. The result of this formula is called the Normalized Difference Vegetation Index (NDVI). To determine the density of green on a patch of land, researchers must observe the distinct colors (wavelengths) of visible and near-infrared sunlight reflected by the plants. As can be seen through a prism, many different wavelengths make up the spectrum of sunlight.  Overview. This article provides an overview of Normalized Differential Vegetation Index (NDVI) maps, an index used to estimate the quantity, quality and development of crops, measured through remote sensing from aerial or satellite systems, capturing the reflection of different wavebands emitted by the crops. The NDVI is an index calculated based on the radiation of remote sensing reflection bands: NIR and RED are the reflectance of the near-infrared and red bands; in the particular case of Landsat images, it corresponds to bands 4 and 3.
http://www47.homepage.villanova.edu/guillaume.turcotte/studentprojects/arboretum/NDVI.htm http://glcf.umd.edu/data/ndvi/ http://www.bom.gov.au/climate/austmaps/about-ndvi-maps.shtml https://en.wikipedia.org/wiki/Normalized_Difference_Vegetation_Index http://phenology.cr.usgs.gov/ndvi_foundation.php http://www.wikiagro.com/en/NDVI_-_Vegetation_Index http://earthobservatory.nasa.gov/Features/MeasuringVegetation/ http://earthobservatory.nasa.gov/Features/MeasuringVegetation/measuring_vegetation_2.php http://www.wikiagro.com/en/NDVI_-_Vegetation_Index
what is ndvi