With the raster calculator, we can create a new raster layer based on the values in one or more rasters that are loaded in the current QGIS project. To access this, go to Raster | Raster Calculator. All available Raster Bands are presented in a list in the top-left corner of the dialog using the raster_name@band_number format.
Continuing from our previous exercise in which we created a slope raster, we can, for example, find areas at elevations above 1,000 meters and with a slope of less than 5 degrees using the following expression:
"srtm_05_01@1" > 1000 AND "slope@1" < 5
You might have to adjust the values depending on the dataset you are using. Check out the Accessing raster and vector layer statistics section ...
