def ring_is_clockwise(ring):
    """
    Determine if polygon ring coordinates are clockwise. Clockwise signifies
    outer ring, counter-clockwise an inner ring or hole. this logic was found
    at http://stackoverflow.com/questions/1165647/how-to-determine-if-a-list-of-polygon-points-are-in-clockwise-order
    this code taken from http://esri.github.com/geojson-utils/src/jsonConverters.js by James Cardona (MIT lisense)
    """
    total = 0
    for (pt1, pt2) in pairwise(ring):
        total += (pt2[0] - pt1[0]) * (pt2[1] + pt1[1])
    return total >= 0