code: def ApproximateDistance(degree_lat1, degree_lng1, degree_lat2, degree_lng2):
    
    # TODO: change to ellipsoid approximation, such as
    # http://www.codeguru.com/Cpp/Cpp/algorithms/article.php/c5115/
    lat1 = math.radians(degree_lat1)
    lng1 = math.radians(degree_lng1)
    lat2 = math.radians(degree_lat2)
    lng2 = math.radians(degree_lng2)
    dlat = math.sin(0.5 * (lat2 - lat1))
    dlng = math.sin(0.5 * (lng2 - lng1))
    x = dlat * dlat + dlng * dlng * math.cos(lat1) * math.cos(lat2)
    return EARTH_RADIUS * (2 * math.atan2(math.sqrt(x),
        math.sqrt(max(0.0, 1.0 - x))))
docs: Compute approximate distance between two points in meters. Assumes the
    Earth is a sphere.