NML:List of tile classes

TILE_CLASS_GROUND	Clear ground and farmland
TILE_CLASS_RAIL	Rail and rail depots
TILE_CLASS_ROAD	Road, road depots and level crossings
TILE_CLASS_HOUSE	Houses
TILE_CLASS_TREES	Clear tile with trees
TILE_CLASS_STATION	Station, waypoint, station part of oilrig
TILE_CLASS_WATER	Sea, canal, ship depot
TILE_CLASS_INDUSTRY	Industry tile
TILE_CLASS_TUNNEL_BRIDGE	Tunnel entrance or bridge ramp
TILE_CLASS_OBJECTS	Objects