Normalized Difference Vegetation Index

NDVI Stands for Normalized Difference Vegetation Index

1. Normalized Difference Vegetation Index By Qazi Muhammad Ehzaz Ul Mohiz 19-GIS-20

2. Contents What is NDVI? How do you Calculate NDVI? Applications How To Interpret NDVI Images? NDVI Specifications

3. NDVI NDVI stands for Normalized Difference Vegetation Index . NDVI was introduced by Tarpley and Kogan in 1980’s with the NOAA (National Oceanic and Atmospheric Administration) in United States. There are round about 26 to 28 vegetation indices, like Image R ationing and Image Differencing , among which NDVI is most popular and accurate vegetation been used. This vegetation index is used to study the properties of different vegetation. NDVI quantifies vegetation by measuring the difference between near-infrared (which vegetation strongly reflects) and red light (which vegetation absorbs ) It focuses on health of vegetation and separate healthy vegetation from other features.

4. How do you calculate NDVI? As shown below,  Normalized Difference Vegetation Index (NDVI)  uses the NIR and red channels in its formula . (NIR - R) / (NIR + R) In Landsat 4-7, NDVI = (Band 4 – Band 3) / (Band 4 + Band 3). In Landsat 8-9, NDVI = (Band 5 – Band 4) / (Band 5 + Band 4). It is calculated in Raster Calculator tool of ESRI Arc GIS. Healthy vegetation(chlorophyll ) reflects more near-infrared (NIR) and green light compared to other wavelengths, But it absorbs more red and blue light. This is why our eyes see vegetation as the  color green , If you could see near-infrared, then it would be strong for vegetation too. Satellite sensors like  Landsat  and  Sentinel-2  both have the necessary bands with NIR and red .

5. Normalized Difference Vegetation Index NDVI always scientific ranges from -1 to +1. When you have values less than zero , it represent all other features rather than vegetation. When you have values more than zero, it represent all kind of vegetation. When you have values close to zero , there are likely no green leaves and it could even be an urbanized area . Dead Plants-------------------- -1-0 Unhealthy Plants-------------- 0-0.33 Moderate Healthy Plants----- 0.33-0.66 Very Healthy Plants----------- 0.66-1

6. Applications We see several sectors using NDVI. For example, in agriculture, farmers use NDVI for precision farming and to measure biomass. Whereas, in forestry, foresters use NDVI to quantify forest supply and leaf area index. Furthermore, NASA states that  ” NDVI is a good indicator of drought” When water limits vegetation growth, it has a lower relative NDVI and density of vegetation. It is u sed for identifying and monitoring droughts affecting agriculture. In reality, there are various of applications where NDVI are being applied in the real world.

7.  How To Interpret NDVI Images? Traditionally, NDVI results are presented as a color map, where each color corresponds to a certain range of values. There’s no standard color palette, but most software uses the “red-green” one, meaning that red-orange-yellow tints indicate bare soil or dead/sparse vegetation, and all shades of green are a sign of normal to dense vegetation cover. EOSDA Land Viewer

8. By USGS

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