12B: zeros
4B float: always 0x3f000000 (0.5)
4B float: terrain height scale 
4B float: always 0x3f000000
2B int  : tile count
2B int  : ?
4B int  : offset to tiles
4B int  : offset to some data?
2B int  : width in BLK
2B int  : height in BLK
array[width * height] of 2B int: tile indices
xB ?
tiles
{
    2B int: texmap idx (from texture index file)
    1B int: ?
    1B uint: lo - minimum height in tile (probably for terrain LOD?)
    1B uint: hi - maximum height in tile
    array[25] of uint8: - 5x5 heights
}
2B 0x0000