def _dms_to_dd(degrees, minutes, seconds, direction):
    """Helper function converting Degrees/Minutes/Seconds to Decimal Degrees
    
    Degrees, minutes, and seconds are numeric types.
    Direction is a single character: 'N', 'E', 'S', or 'W'.
    The type returned shall be a floating point number.
    """
    if direction == 'N' or direction == 'E':
        return degrees + (minutes / 60.) + (seconds / 3600.)
    else:
        return -1 * (degrees + (minutes / 60.) + (seconds / 3600.))