Height data with a sample interval of one arc second (3600 samples per degree) gives better terrain shading than the standard data with a sample interval of three arc seconds (1200 samples per degree). This image was generated from USGS-style HGT files downloaded from Jonathan de Ferranti's ViewFinder Panoramas site. The high-resolution data covers the whole of North America and a few other areas, including much of the Alps.
CartoType's data preparation tool, makemap, can now handle data in this format automatically. It determines whether an HGT file contains 1-second or 3-second data from its size. There's also a new command line option to control the angle of the sun used for hill shading. The standard angle, as ued here, is 315 degrees (north west) although in fact the sun is rarely in the north-west in the northern hemisphere.
The full command line used to create the map was:
makemap /res=5 /lowreslayers=yes /urbanareas=yes /project=utme /sun=315 /extent=7,45,8,47 /interval=30 /terrain=shadow /usgs=\height-data-high-res /terrain=height-feet /usgs=\height-data-high-res /input=coastlines.xml w7-s45-e8-n47.osm western-alps.ctm1
However, I turned off the urban area layer for the screen shot.