A common task in producing maps is to mix different layers in a single output. This causes some masking of the overlapping objects, as we explored in the previous recipe. When you work with the raster data, of course, masking is an issue as the top raster layer could totally hide the bottom layers.
In this recipe, we'll explore how to use transparency to avoid masking and merge several raster layers in a single map.
In the Rendering transformations for raster data recipe of Chapter 3, Advanced Styling, we downloaded a dataset from USGS to explore how rendering works for raster data. We will now use the same dataset, producing a complementary dataset.
Note
If you didn't read Chapter 3, Advanced Styling, you should at least download and publish the DEM following the instructions given in the Rendering transformations for raster data recipe in Chapter 3.
We will use the gdaldem
tool, available among the GDAL command utilities, to create a shaded relief...