Revision as of 09:57, 27 November 2020

Spectral vegetation index using Raster Calculator

Click the Open Data Source Manager and then Add raster layer and select the file /geodata/lucc/s2/Subset_S2A_MSIL2A_20170619T_MUL.tif.
Check the rank and spectral range of bands in the multiband file (e.g. see table Changing Raster Layer Style).
Click Raster --> Raster calculator.
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:

Define path and file name of the output layer. OK.
Map visualization: Open the raster layer properties by right-clicking the ndvi raster in the TOC selecting Properties, or by simply double clicking.
Select the Symbology tab. Under Render type select Singleband pseudocolor.
- Open the In the pulldown menu of Color ramp by clicking on Select All color ramps --> RdYlGn. In the Mode select Equal interval. Set the number of Classes to 10. In the pulldown menu of Color ramp select Invert Color Ramp.

A convenient module for calculating one or several spectral indices at the same time can be found in the QGIS processing toolbox.

Type Radiometric into the search field and find the OTB --> Feature Extraction --> Radiometric Indices tool.
Open it with a double click.
Assign the bands in the multiband file to the correct spectral sensitivity.
If you want to calculate a single spectral index type in the text field Available Radiometric Indices: "Vegetation:NDVI"
If you want to calculate several spectral indices at once and store them in a multiband file click Help to find definitions of available spectral indices in three categories (vegetation, water, soil) and relevant channels of the input multiband image.
In the text field Available Radiometric Indices type with apostrophs:

"Vegetation:NDVI Water:NDWI Soil:BI2"

Figure A: Single band NDVI (color table = RdYlGn)	Figure B: Spectral composite (RGB = NDVI,BI2,NDWI)

@@ Line 19: / Line 19: @@
 * If you want to calculate a single spectral index type in the text field ''Available Radiometric Indices'': {{typed|text="Vegetation:NDVI"}}
 * If you want to calculate several spectral indices at once and store them in a multiband file click {{button|text=Help}} to find definitions of available spectral indices in three categories (vegetation, water, soil) and relevant channels of the input multiband image.
-* Click {{button|text=Run}}.
 * In the text field ''Available Radiometric Indices'' type with apostrophs:
 {{typed|text="Vegetation:NDVI Water:NDWI Soil:BI2"}}
 [[File:Qgis_radiometric_composite.png|left|400px]]
+* Click {{button|text=Run}}.
 {| class="wikitable"
 | style="border: 0pt" | [[file:Qgis_ndvi_pseudo.png|thumb|left|400px|'''Figure A: ''' Single band '''NDVI''' (color table = RdYlGn)]]