With the added increase in normal map quality while using the uncompressed dds format these 'artefacts' actually take on some shape. See the pictures below...
In the above picture, the top ~3/4 of the picture has a 32k uncompressed normal map and the bottom ~1/4 has a 16k dxt3 normal map. It's as clear as day that the artefacts in the 16k compressed map resolve themselves into sand dunes in the uncompressed version. Most of the GLOBE DEM data around the sahara region is of low resolution, as can be seen from the dunes visible on a large scale in the centre portion of the picture(low resolution) and on a small scale in the top portion(high resolution).
A similiar situation exists for the himilaya region were most of the height data of the desert seems to be high res...
These 'non artefacts' are also most visible when using uncompressed normal maps for mars(where the whole planet is now covered in them) . In this case though using dxt3 virtually eliminates them(they are quite ugly)...
Uncompressed u888
Compressed dxt3
Perhaps the limitations of the compressed dxt format are useful after all.
