Land Cover/Use Classification using the Semi-Automatic Classification Plugin for QGIS
From AWF-Wiki
Contents |
Working steps
Preparing raster data (Converting DN to reflectance)
- Load the multiband raster file Subset_S2A_MSIL2A_20170619T.tif available in the course data. This contains all 13 bands of Sentinel-2 scene.
- Follow Split stack to extract bands 2, 3, 4, 5, 6, 7, 8, 11 and 12, using the multiband raster file Subset_S2A_MSIL2A_20170619T.tif as input layer.
- In the processing toolbar, type Raster calculator into the search field to find the GDAL\OGR --> Raster calculator tool and open it.
- Click the button Run as batch process..., and use Add row button to add enough processing rows.
- Click the button ... of Input layer A to select the single extracted bands as input layers (i.e. one per row).
- Enter and repeat the expression A/10000 under Calculation in gdalnumeric syntax using +-/* or any numpy array functions (i.e. logical_and()) and set Output raster type to Float32
- Click the button ... of Calculated to save output file
- Click Run
- Follow Create stack to create a multiband raster file from the converted single bands from step 3 and load into QGIS canvas
Install and set up SCP plugin
- Click Plugins --> Manage and Install Plugins
- Type in the search bar semi-Automatic Classification, click on the plugin name and then on Install plugin.
- Right-click on the Plugin Toolbar and make sure the following are checked SCP Dock, SCP Edit Toolbar, SCP Tools and SCP Working Toolbar.
Defining classification inputs in SCP-plugin
We need to define input image, training input and spectral signature files for SCP.
- Open the SCP Dock.
- Click SCP Dock --> SCP input --> Input image, use the button Refresh list and the drop-down menu-bar to select the multiband Merge file (i.e. from DN to Reflectance conversion) as input image.
- Click the button Band set to further define the input image
- Next, click Quick wavelength settings and select Sentinel-2 from the list in order to automatically set the Center wavelength for each band and the Wavelength unit (NB. required for spectral signature assessment)