Also notice that all this talks about making a 1024x1024 8bit grayscale bmp file, which can be imported to TE.
If you want to edit the .ELV file, it is a bit different. It can be renamed as .RAW and opened in Photoshop. Notice that the bitmap is mirrored vertically and it looks different because the alt info is spread wider (more than 256 levels) in to smaller more accurate units. This is done by using the alpha channel starting from 0 for each "elevation range". This way the ELV file can contain 256x256 levels.
This same RAW technique can be used for TYP and SYP files to edit the terrain types and subtypes. Although the subtype editing cannot be controlled too well, but at least applying noise on the file will randomize the wanted areas.
The TYP file simply uses RGB levels from 0,0,0 to 6,6,6 as the different texture types for each square mile.
