def check_tile_id(tile_id):
    """
    Raise a ``ValueError`` if the given SRTM tile ID (string) 
    is improperly formatted.
    Otherwise, return nothing.
    """
    t = tile_id
    msg = '{!s} is not a valid STRM tile ID'.format(t)
    try:
        lat = int(t[1:3])
        lon = int(t[4:])
    except:
        raise ValueError(msg)
    if not (t[0] in ['N', 'S'] and t[3] in ['E', 'W'] and 0 <= lat <= 90 and
        0 <= lon <= 180):
        raise ValueError(msg)
