Google Maps

This is a cool application of clustering. It uses the application of javascript to solve problem of over-crowdedness of markers on the google earth and maps. To relieve the problem ,we apply hard, near-neighbour clustering . the javascript library has the name: MarkerCluster, and its effect can be seen as :

It's easy to use - just add your markers to an array, pass that and your map into the MarkerClusterer, and it'll take care of the rest. Check out the simple example and code snippet below:

var markers = [];

for (var i = 0; i < 100; ++i)
{
var latlng = new GLatLng(data.photos[i].latitude, data.photos[i].longitude);
var marker = new GMarker(latlng);
markers.push(marker);
}
var markerCluster = new MarkerClusterer(map, markers);

Here the latlng is for the latitude and longitude application ,the two parameters that are taken are coordinates
of the point where the marjers are to be specified. We push the new marker to the set of markers and enable
clustering yet again. The  MarkerClusterer function

To use a marker clusterer, create a MarkerClusterer object. In the simplest case, just pass a map to it.

var map = new GMap2(document.getElementById("map"));
map.setCenter(new GLatLng(37.4419, -122.1419), 13);
var mc = new MarkerClusterer(map);

You may also specify a number of options to fine-tune the marker manager's performance. These options are passed via a MarkerClustererOptions object. The MarkerClustererOptions object is an object literal, so you simply declare the object without a constructor:

var map = new GMap2(document.getElementById("map"));
map.setCenter(new GLatLng(37.4419, -122.1419), 13);
var mcOptions = {gridSize: 50, maxZoom: 15};
var mc = new MarkerClusterer(map, [], mcOptions);

Once you create a marker cluster, you will want to add markers to it. MarkerClusterer supports adding markers using the addMarkers() method or by providing a array of markers to the constructor:

var map = new GMap2(document.getElementById("map"));
map.setCenter(new GLatLng(37.4419, -122.1419), 13);
var mcOptions = { gridSize: 50, maxZoom: 15};
var markers = [...]; // Create the markers you want to add and collect them into a array.
var mc = new MarkerClusterer(map, markers, mcOptions);

A Simple MarkerClusterer Example:

This example will show 100 markers on map.

  if(GBrowserIsCompatible()) {
   map = new GMap2($('map'));
   map.setCenter(new GLatLng(39.91, 116.38), 2);
   map.addControl(new GLargeMapControl());

   var markers = [];
   for (var i = 0; i < 100; ++i) {
     var latlng = new GLatLng(data.photos[i].latitude, data.photos[i].longitude);
     var marker = new GMarker(latlng);
     markers.push(marker);
   }
   var markerCluster = new MarkerClusterer(map, markers);