void dfw(IMongoCollection <BsonDocument> collection, int minZoom, int maxZoom)
        {
            GlobalMercator proj = new GlobalMercator();



            string quadDallas  = proj.latlngToQuadKey(32.7805664, -96.8081442, minZoom);
            string quadFtWorth = proj.latlngToQuadKey(32.7586487, -97.3324023, minZoom);

            List <string> quads = new List <string>();

            quads.Add(quadDallas);
            quads.Add(quadFtWorth);


            foreach (string quad in quads)
            {
                process(quad, collection, maxZoom);
            }
        }
        void cities(IMongoCollection <BsonDocument> collection, int minZoom, int maxZoom)
        {
            GlobalMercator proj = new GlobalMercator();



            string quadDallas       = proj.latlngToQuadKey(32.7805664, -96.8081442, minZoom);
            string quadFtWorth      = proj.latlngToQuadKey(32.7586487, -97.3324023, minZoom);
            string quadHouston      = proj.latlngToQuadKey(29.758169, -95.3684179, minZoom);
            string quadLosAngeles   = proj.latlngToQuadKey(34.0507041, -118.243092, minZoom);
            string quadSanFrancisco = proj.latlngToQuadKey(37.7608648, -122.4153602, minZoom);
            string quadSeattle      = proj.latlngToQuadKey(47.6059903, -122.3292994, minZoom);
            string quadChicago      = proj.latlngToQuadKey(41.8814234, -87.6292672, minZoom);
            string quadAtlanta      = proj.latlngToQuadKey(33.7515908, -84.3858375, minZoom);
            string quadNewYork      = proj.latlngToQuadKey(40.7322625, -73.9924373, minZoom);
            string quadBoston       = proj.latlngToQuadKey(42.3742784, -71.1165778, minZoom);
            string quadDetroit      = proj.latlngToQuadKey(42.3314207, -83.0458919, minZoom);
            string quadAustin       = proj.latlngToQuadKey(30.2682476, -97.7417557, minZoom);
            string quadDC           = proj.latlngToQuadKey(38.9073708, -77.0363579, minZoom);

            List <string> quads = new List <string>();

            quads.Add(quadDallas);
            quads.Add(quadFtWorth);
            quads.Add(quadNewYork);
            quads.Add(quadHouston);
            quads.Add(quadSanFrancisco);
            quads.Add(quadLosAngeles);
            quads.Add(quadBoston);
            quads.Add(quadAustin);
            quads.Add(quadAtlanta);
            quads.Add(quadChicago);
            quads.Add(quadDC);
            quads.Add(quadSeattle);
            quads.Add(quadDetroit);



            foreach (string quad in quads)
            {
                process(quad, collection, maxZoom);
            }
        }