Spectral indices
From AWF-Wiki
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= Several spectral indices at once using Processing Toolbox = | = 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. | A convenient module for calculating one or several spectral indices at the same time can be found in the QGIS processing toolbox. | ||
| − | * Type {{typed|text=Radiometric}} into the search field and find the {{button|text=OTB --> Feature Extraction --> Radiometric Indices | + | * Type {{typed|text=Radiometric}} into the search field and find the {{button|text=OTB --> Feature Extraction --> Radiometric Indices}} tool. |
* Open it with a double click. | * Open it with a double click. | ||
* Assign the bands in the multiband file to the correct spectral sensitivity. | * Assign the bands in the multiband file to the correct spectral sensitivity. | ||
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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)]] | ||
| − | | style="border: 0pt" | [[file:Qgis_vi_composite.png|thumb|left|400px|'''Figure B: '''Spectral composite (RGB = NDVI | + | | style="border: 0pt" | [[file:Qgis_vi_composite.png|thumb|left|400px|'''Figure B: '''Spectral composite (RGB = NDVI,BI2,NDWI)]] |
|} | |} | ||
[[Category:Working with Raster Data]] | [[Category:Working with Raster Data]] | ||
[[Category:Tutorials]] | [[Category:Tutorials]] | ||
Revision as of 11:23, 17 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).
- After clicking Open, the raster layer appears in the QGIS canvas.
- 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 Style 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 and click Classify.
- To finish, click Apply (see Fig. A).
- Open the In the pulldown menu of Color ramp by clicking on
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.
- Click Run.
- In the text field Available Radiometric Indices type with apostrophs:
"Vegetation:NDVI Water:NDWI Soil:BI2"
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