def poly_compare(poly1, poly2, area):
    """Calculate the ratio of overlap between two polygons and the given area

    :param poly1: polygon specified by its verticies
    :type poly1: list
    :param poly2: polygon specified by its verticies
    :type poly2: list
    :param area: the area to compare the overlap of poly1 and poly2
    :type area: float
    :return: the ratio of overlap of poly1 and poly2 to the area  e.g. overlap(poly1, poly2)/area
    :rtype: float
    """
    assert area > 0
    intersection_area = help.polygon_intersection_area([poly1, poly2])
    return intersection_area / area
