code: def size(self):
  		'''return tile size as (width,height) in meters'''
  		(lat1, lon1) = self.coord((0,0))
  		(lat2, lon2) = self.coord((TILES_WIDTH,0))
  		width = mp_util.gps_distance(lat1, lon1, lat2, lon2)
  		(lat2, lon2) = self.coord((0,TILES_HEIGHT))
  		height = mp_util.gps_distance(lat1, lon1, lat2, lon2)
  		return (width,heightf size(self):
  		'''return tile size as (width,height) in meters'''
  		(lat1, lon1) = self.coord((0,0))
  		(lat2, lon2) = self.coord((TILES_WIDTH,0))
  		width = mp_util.gps_distance(lat1, lon1, lat2, lon2)
  		(lat2, lon2) = self.coord((0,TILES_HEIGHT))
  		height = mp_util.gps_distance(lat1, lon1, lat2, lon2)
  		return (width,height)
docs: return tile size as (width,height) in meters