Stefano Rivella - The NDVI Index is then computed using the...

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Stefano Rivella MPO 553 HW #3 One of the possible applications of remote sensing is the measure of vegetation cover, through the “Normalized Difference Vegetation Index” (NDVI). Figure 1 – NDVI Index - http://earthobservatory.nasa.gov/GlobalMaps/view.php?d1=MOD13A2_M_NDVI The two images above represent the vegetation cover during January and August 2011, using the NDVI Index. Vegetation emits and absorbs radiation at different wavelengths. The pigment in plant leaves, chlorophyll, strongly absorbs visible light (0.4 - 0.7 µm) for use in photosynthesis, and reflects near-infrared light (0.7 – 1.1 µm). Depending on the amount of leaves of the plant, the ratio of visible light absorbed/reflected is different.
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To take measures of the NDVI Index, the NOAA AHVRR (Advanced Very High Resolution Radiometer ) makes use of different detectors (each tuned on a different wavelength range) in order to measure the intensity of light, both in the visible and near-infrared wavelengths.
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Unformatted text preview: The NDVI Index is then computed using the following formula NDVI = (NIR — VIS)/(NIR + VIS) where NIR is the near infrared radiation and VIS is the visible radiation. The higher the index, the greener is the land, while a index close to zero means no vegetation. Figure 2 – NDVI physical meaning - http://earthobservatory.nasa.gov/Features/MeasuringVegetation/measuring_vegetation_2.php The idea behind this index is that if the difference between NIR and VIS is higher, it means that the selected pixel (the resolution is 1 km x 1 km) is densely green, while if this difference is lower (low absorption of visible light), then the vegetation is sparse or not present (grassland, tundra, desert). REFERENCES: http://earthobservatory.nasa.gov/Features/MeasuringVegetation/measuring_vegetation_2.php http://earthobservatory.nasa.gov/GlobalMaps/view.php?d1=MOD13A2_M_NDVI...
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This note was uploaded on 01/08/2012 for the course MPO 551 taught by Professor Zhang,c during the Summer '08 term at University of Miami.

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Stefano Rivella - The NDVI Index is then computed using the...

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