google maps cluster work

google.load('jquery', '1.3');
google.load("maps", "2");
google.load("visualization", "1", {packages:["linechart"]});
google.setOnLoadCallback(function(){
  $(document).ready(function(){
    var map = new google.maps.Map2(document.getElementById("main_map"));
    map.setCenter(new google.maps.LatLng(37.4419, -122.1419), 5);
    
    // generate random points
    var all_markers = new Array();
    var bounds = map.getBounds();
    var southWest = bounds.getSouthWest();
    var northEast = bounds.getNorthEast();
    var lngSpan = northEast.lng() - southWest.lng();
    var latSpan = northEast.lat() - southWest.lat();
    for (var i = 0; i < 100; i++) all_markers.push({"lat":southWest.lat() + latSpan * Math.random(), "lng":southWest.lng() + lngSpan * Math.random()});
    var clusters = [];
    var max_distance = calc_max_distance();
    var singles = [];
    var checked_markers = all_markers.slice();
    while(checked_markers.length > 0){
      var current_marker = checked_markers.pop();
      for (var i = clusters.length - 1; i >= 0; i--){
        if(haversine_distance(current_marker,clusters[i].center) < max_distance){
          
        }
      };
      for (var i = checked_markers.length - 1; i >= 0; i--){
        if(haversine_distance(current_marker,checked_markers[i]) < max_distance){
          close_marker = checked_markers.splice(i,1);
          close_marker = close_marker[0];
          if(current_marker.cluster) addMarkerToCluster(close_marker, current_marker.cluster);
          else createCluster(current_marker,close_marker);
        }
      }
      if(!current_marker.cluster) singles.push(current_marker);
    }
    //console.log(clusters);
    //console.log(singles);
    for(var i = 0; i < clusters.length; i++){
      var centerpoint = new GMarker(new GLatLng(clusters[i].markers[0].lat,clusters[i].markers[0].lng));
      centerpoint.other_markers = clusters[i].markers;
      //map.addOverlay(centerpoint);
      drawCircle(new GLatLng(clusters[i].markers[0].lat, clusters[i].markers[0].lng), max_distance, 32);
      GEvent.addListener(centerpoint, "click", function() {
        display_markers(this.other_markers);
      });
    }

    for(var i = 0; i < all_markers.length; i++){
      map.addOverlay(new GMarker(new GLatLng(all_markers[i].lat,all_markers[i].lng)));
    }
    
    function addMarkerToCluster(marker,cluster){
      cluster.markers.push(marker);
      marker.cluster = cluster;
    }
    
    function combineClusters(cluster1,cluster2){
      // if(cluster1.markers.length > cluster2.markers.length){
      //   var tmp_cluster = cluster1;
      //   cluster1 = cluster2;
      //   cluster2 = tmp_cluster;
      // }// swap to only step over the smallest one
      for (var i=0; i < cluster1.markers.length; i++) {
        addMarkerToCluster(cluster1.markers[i],cluster2);
      };
    }
    
    function createCluster(){
      var new_cluster = {markers:[]};
      for (var i=0; i < arguments.length; i++) {
        new_cluster.markers.push(arguments[i]);
      };
      clusters.push(new_cluster);
      return new_cluster;
    }
    
    function display_markers(markers){
      for(var i in markers){
        map.addOverlay(new GMarker(new GLatLng(markers[i].lat,markers[i].lng)));
      }
    }
    
    function calc_max_distance() { //gets distance in km of 32 pixels
      var p1 = map.fromContainerPixelToLatLng(new GPoint(0,0));
      var p2 = map.fromContainerPixelToLatLng(new GPoint(32,32));
      return p1.distanceFrom(p2) / 1000;
    }
    
    function drawCircle(center, radius, nodes, liColor, liWidth, liOpa, fillColor, fillOpa){
    	//calculating km/degree
    	var latConv = center.distanceFrom(new GLatLng(center.lat()+0.1, center.lng()))/100;
    	var lngConv = center.distanceFrom(new GLatLng(center.lat(), center.lng()+0.1))/100;

    	//Loop 
    	var points = [];
    	var step = parseInt(360/nodes)||10;
    	for(var i=0; i<=360; i+=step)
    	{
    	var pint = new GLatLng(center.lat() + (radius/latConv * Math.cos(i * Math.PI/180)), center.lng() + 
    	(radius/lngConv * Math.sin(i * Math.PI/180)));
    	points.push(pint);
      bounds = new GLatLngBounds();
    	bounds.extend(pint); //this is for fit function
    	}
    	points.push(points[0]); // Closes the circle, thanks Martin
    	fillColor = fillColor||liColor||"#0055ff";
    	liWidth = liWidth||2;
    	var poly = new GPolygon(points,liColor,liWidth,liOpa,fillColor,fillOpa);
    	map.addOverlay(poly);
    }

  });
});

Number.prototype.toRad = function() { // convert degrees to radians
  return this * Math.PI / 180;
}

function haversine_distance(point_a,point_b){
  var R = 6371; // km
  var dLat = (point_a.lat - point_b.lat).toRad();
  var dLon = (point_a.lng - point_b.lng).toRad();
  var a = Math.sin(dLat/2) * Math.sin(dLat/2) +
          Math.cos(point_b.lat.toRad()) * Math.cos(point_a.lat.toRad()) *
          Math.sin(dLon/2) * Math.sin(dLon/2);
  var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
  var d = R * c;
  return d;
}