Spectral indices
From AWF-Wiki
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* In the text field ''Available Radiometric Indices'' type with apostrophs: | * In the text field ''Available Radiometric Indices'' type with apostrophs: | ||
{{typed|text="Vegetation:NDVI Water:NDWI Soil:BI2"}} | {{typed|text="Vegetation:NDVI Water:NDWI Soil:BI2"}} | ||
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[[File:Qgis_radiometric_composite.png|left|400px]] | [[File:Qgis_radiometric_composite.png|left|400px]] | ||
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* Click {{button|text=Run}}. | * Click {{button|text=Run}}. | ||
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{| class="wikitable" | {| class="wikitable" | ||
| style="border: 0pt" | [[file:Qgis_ndvi_pseudo.png|thumb|left|400px|'''Figure A: ''' Single band '''NDVI''' (color table = RdYlGn)]] | | style="border: 0pt" | [[file:Qgis_ndvi_pseudo.png|thumb|left|400px|'''Figure A: ''' Single band '''NDVI''' (color table = RdYlGn)]] |
Revision as of 09:58, 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.
- To finish, click Apply (see Fig. A).
Several spectral indices at once using Processing Toolbox
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"
- Click Run.