Spectral indices
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* Map visualization: Open the raster layer properties by right-clicking the ndvi raster in the [[TOC]] selecting {{button|text=Properties}}, or by simply double clicking. | * Map visualization: Open the raster layer properties by right-clicking the ndvi raster in the [[TOC]] selecting {{button|text=Properties}}, or by simply double clicking. | ||
* Select the {{button|text=Symbology}} tab. Under '''Render type''' select {{button|text=Singleband pseudocolor}}. | * Select the {{button|text=Symbology}} tab. Under '''Render type''' select {{button|text=Singleband pseudocolor}}. | ||
| − | ** Open the | + | ** Open the the pulldown menu of {{button|text=Color ramp}} by clicking on [[File:Qgis_pull_down.png]] Select {{mitem|text= All color ramps --> RdYlGn}}. Under {{button|text=Mode}} select {{button|text=Equal interval}}. Set the number of {{button|text=Classes}} to 10. In the pulldown menu of {{button|text=Color ramp}} select {{mitem|text=Invert Color Ramp}}. |
** To finish, click {{button|text=Apply}} (see '''Fig. A'''). | ** To finish, click {{button|text=Apply}} (see '''Fig. A'''). | ||
| − | = Several spectral indices at once using | + | = Several spectral indices at once using OTB = |
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}} tool. | * Type {{typed|text=Radiometric}} into the search field and find the {{button|text=OTB --> Feature Extraction --> Radiometric Indices}} tool. | ||
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* 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, soil, water) and relevant channels of the input multiband image. | * 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, soil, water) and relevant channels of the input multiband image. | ||
* In the text field ''Available Radiometric Indices'' type with apostrophs: | * In the text field ''Available Radiometric Indices'' type with apostrophs: | ||
| − | {{typed|text="Vegetation:NDVI Soil:BI2 | + | {{typed|text="Vegetation:NDVI Water:NDWI2 Soil:BI2"}} |
* Click {{button|text=Run}}. | * Click {{button|text=Run}}. | ||
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[[Category:Working with Raster Data]] | [[Category:Working with Raster Data]] | ||
| + | [[Category:QGIS Tutorial]] | ||
[[Category:Tutorials]] | [[Category:Tutorials]] | ||
Latest revision as of 18:03, 14 June 2021
[edit] 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). Here the rank of 10 bands is B2,B3,B4,B5,B6,B7,B8,B8A,B11,B12.
- 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 the pulldown menu of Color ramp by clicking on
Select All color ramps --> RdYlGn. Under Mode select Equal interval. Set the number of Classes to 10. In the pulldown menu of Color ramp select Invert Color Ramp.
- Open the the pulldown menu of Color ramp by clicking on
- To finish, click Apply (see Fig. A).
[edit] Several spectral indices at once using OTB
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, soil, water) and relevant channels of the input multiband image.
- In the text field Available Radiometric Indices type with apostrophs:
"Vegetation:NDVI Water:NDWI2 Soil:BI2"
- Click Run.
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