hi there:
I have a google map with several placemarks, when you zoom out on it at some point several placemarks that are close, show as one, in the domain of the app this is a serious problem.
Is there anyway to show some sort of count or make obvious the fact that there are more than one placemark?
Cheers
There's an extension by Martin Pearman that addresses this situation:
ClusterMarker detects any groups of two or more markers whose icons visually intersect when displayed. Each group of intersecting markers is then replaced with a single cluster marker. The cluster marker, when clicked, simply centres and zooms the map in on the markers whose icons previously intersected.
There seems to be a problem with the redirection on Martin's page at the moment, but if you keep reloading it eventually works.
MarkerClusterer was recently released on the GMaps Utility Library. It's the fastest client-side clusterer I've seen so far. There's a great example here which shows some of the options you can tweak.
This page compares and benchmarks some of the options available to you, and concludes that MarkerClusterer is the fastest.
Just keep in mind that if you have several thousand markers, any client-side solutions will probably be too slow.