var map;
        function TreeMap(div,extent,json) {
            map = new OpenLayers.Map(div,
                    { 
                        projection: new OpenLayers.Projection("EPSG:900913"),
                        displayProjection: new OpenLayers.Projection("EPSG:4326"),
                        units: "m",
                        numZoomLevels: 20,
                        maxResolution: 156543.0339,
                        maxExtent: new OpenLayers.Bounds(-20037508.34, -20037508.34,
                            20037508.34, 20037508.34)
                    });

            var baselayer = new OpenLayers.Layer.Google(
                    "Google Physical",
                    {sphericalMercator: true,
                    type: G_PHYSICAL_MAP
                });
                       
          // check to see if we are on the home page           
          if (div == 'home-map') {
            var JSON_style = new OpenLayers.StyleMap({ 
                "default": new OpenLayers.Style({
                    pointRadius: 10,
                    fillColor: "#c5adde",
                    fillOpacity: .8, 
                    strokeColor: "#2d2833",
                    strokeWidth: 6, 
                    strokeOpacity: .4,  
                    cursor: "pointer"  
                })
            }); 
            var geojson_format = new OpenLayers.Format.GeoJSON();
            var JSONfeatures = new OpenLayers.Layer.Vector("New York City Boroughs",{styleMap: JSON_style}); 
            map.addLayer(JSONfeatures);
            JSONfeatures.addFeatures(geojson_format.read(json));
        } ; 

           map.addLayers([baselayer]);
                       
           map.addControl( new OpenLayers.Control.LayerSwitcher()); 
           map.zoomToExtent(extent);
        }