def to_dec_deg(dms):
    """Convert to decimal degrees."""
    if not dms:
        return 0.0
    deg, minutes = dms.split()
    side = minutes[-1]
    minutes = minutes[:2]
    float_deg = int(deg) + int(minutes) / 60.0
    return float_deg if side in ('N', 'E') else -float_deg
