Spectral indices
From AWF-Wiki
(Difference between revisions)
(→Spectral vegetation index using Raster Calculator) |
(→Several spectral indices at once using OTB) |
||
| (One intermediate revision by one user not shown) | |||
| Line 12: | Line 12: | ||
** 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. | ||
| Line 20: | Line 20: | ||
* 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}}. | ||
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.
 |
 |
