Creating the Slope Map
Once you download QGIS and the data here is a quick run through of how to create the map, with links to additional resources.
The terrain 50 data is published as a set of zip files, one for each 10km x 10km grid square in GB.* The easiest way to use the data is to create a 'virtual mosaic' with GDAL Raster following instructions from the Landscape Laboratory blog. This will automatically unzip and stitch together all the different tiles. * Once you have the VRT you can add the raster grid to QGIS, then with the built in tool Calculate the Slope. This will create a new file that you can save which by default will give a slope value in degrees. * For this map I used the raster calculator to create a mask that removes all slope values less than 27.5°:`(gb_slope_map@1 >= 27.5) * gb_slope_map@1`
The map tiles themselves were created using ESRI ArcGIS Desktop (not free, but available for home use at £100/year), however there are a number of free tools that could be used for this task;