@staticmethod
def find_subsector_id(hex_id):
    """hex_id in range 0000-3240, return subsector ID (A-P)"""
    hex_id_col = int(hex_id[:2]) - 1
    hex_id_row = int(hex_id[2:]) - 1
    try:
        return ['ABCD', 'EFGH', 'IJKL', 'MNOP'][int(hex_id_row / 10)][int(
            hex_id_col / 8)]
    except IndexError:
        print('IndexError: hex_id = {} ({}, {})'.format(hex_id, hex_id_col,
            hex_id_row))
        raise
