Some applications are required to display a large number of locations or markers. Natively plotting thousands of markers on a map can quickly lead to a degraded user experience. Too many markers on the map cause both visual overload and sluggish interaction with the map. To overcome this poor performance, the information displayed on the map needs to be simplified.

One useful optimization technique involves viewport marker management: restricting the markers rendered on the map into only those that exist within the viewable area.

Clustering simplifies the data visualization by consolidating data that are nearby each other on the map in an aggregated form.

References:

• https://developers.google.com/maps/articles/toomanymarkers
• https://googlemaps.github.io/js-marker-clusterer/docs/examples.html
• http://google-maps-utility-library-v3.googlecode.com/svn/trunk/markerclusterer/docs/reference.html
• http://jsfiddle.net/B3a86/2/