15B zeros
1B ? allways 0x3f (63)
4B ?
4B ? allways 0x0000003f (63)
2B tile count
2b ?
4B offset to tiles
4B offset to some data?
2B width in BLK
2B height in BLK
BLK 
{
  width * height * 2B tile indices
}
xB ?
tiles 
{
   2b texmap idx (from texture index file)
   1b ?
   1b lo - minimum height in tile (probably for terrain LOD?)
   1b hi - maximum height in tile
   25B - 5x5 heights
}
2B 0x0000