Raster data, including but not limited to elevation models or remote sensing imagery, is commonly used in many analyses. The following exercises show common raster processing and analysis tasks such as clipping to a certain extent or mask, creating relief and slope rasters from digital elevation models, and using the raster calculator.
A common task in raster processing is clipping a raster with a polygon. This task is well covered by the Clipper tool located in Raster | Extraction | Clipper. This tool supports clipping to a specified extent as well as clipping using a polygon mask layer, as follows:
Extent can be set manually or by selecting it in the map. To do this, we just click and drag the mouse to open a rectangle in the map area of the main QGIS window.
A mask layer can be any polygon layer that is currently loaded in the project or any other polygon layer, which can be specified using Select…, right next to the Mask layer drop-down list.