A raster pyramid is a reduced-resolution version of a raster. The purpose of a pyramid is to reduce the time it takes to display a raster. Pyramids can be built at multiple levels to help strike a balance between the pyramid's file size and the display speed.
To build a raster overview in QGIS, click on Build overviews (Pyramids) by navigating to Raster | Miscellaneous. This will open the Build overviews (Pyramids) tool window, as shown in the following screenshot:
The Build overviews tool provides a few options, as well as the ability to edit the GDAL command that will build the overviews. By selecting Batch mode, an entire directory of rasters will be processed, instead of the default of a single raster. In either case, the following options are available:
.ovr
file. The file will have the same base name as the original input file..aux
file. The file will have the same base name as the original input file.The Build overviews tool is essentially a frontend for the gdaladdo
GDAL command. So, at the bottom of the tool window, the GDAL command is displayed and modified when options are selected. To manually change the GDAL command, press the Edit button ()
to make the GDAL command editable.
The gdaladdo
GDAL command builds or rebuilds pyramids for raster data. For more detailed information about this command and its parameters, visit the documentation page at http://gdal.org/gdaladdo.html.