@@ -27,7 +27,7 @@ When [GDAL](http://www.gdal.org) is installed, the collect script can optionally
To trigger this behavior specify an output filename ending in `.tif`, `.tiff`, or `.geotiff` and **gdal_merge.py** will be called to merge all downloaded tiles into a single image (and removes the intermediate files):
GDAL includes additional analytics, hill shading, and contouring algorithms. For instance, you could run [gdaldem hillshade](http://www.gdal.org/gdaldem.html#gdaldem_hillshade) on the merged file to generate a basic hillshade. Mapbox has a great [tutorial](https://www.mapbox.com/tilemill/docs/guides/terrain-data/#creating-hillshades) with full set of options.