Spectral indices

Revision as of 17:02, 9 November 2017

Vegetation index using the Raster Calculator

1. Click the Add raster layer and select a multiband Sentinel-2 satellite image
2. Check the rank and spectral range of bands in the multiband file (e.g. see table Changing Raster Layer Style).
3. After clicking Open, the raster layer appears in the QGIS canvas.
4. Click Raster --> Raster calculator.
5. A powerful normalization is realized by the normalized difference vegetation index that forms the basis of most vegetation indices $NDVI = (Nir - Red) / (Nir + Red)$. It can be implemented using Raster Calculator as seen in the following screenshot:

1. Define path and file name of the output layer. OK.
2. Map visualization: Open the raster layer properties by right-clicking the ndvi raster in the TOC selecting Properties, or by simply double clicking.
3. Select the Style tab. Under Render type select Singleband pseudocolor.
   1. In the Generate new color map section select RdYlGn. In the Mode pulldown menu select Equal interval. Set the number of Classes to 10 and click Classify.
   2. To finish, click Apply.

Spectral indices using OTB

A convinient module for calculating spectral indices can be found in the processing toolbar. Type Radiometric into the search field and find the Orfeo Toolbox --> Feature Extraction --> Radiometric Indices) tool. Open it with a double click. Assign the spectral ranges to the right order of bands in the multiband file. Choose ndvi from the Availible Radiometric Indices dropdown list. OK.