def get_utm_zone(pos_longlat):
    """
    Return the UTM zone number corresponding to the supplied position

    Arguments:
        pos_longlat: position as tuple (This in (long, lat)

    Returns:
        The UTM zone number (+ve for North, -ve for South)
    """

    lon, lat = pos_longlat
    z = int(lon/6) + 31
    if lat < 0:
        z = -z
    return z