function ClusterMarker($map, $options){
	this._map=$map;
	this._mapMarkers=[];
	this._iconBounds=[];
	this._clusterMarkers=[];
	this._eventListeners=[];
	if(typeof($options)==='undefined'){
		$options={};
	}
	this.borderPadding=($options.borderPadding)?$options.borderPadding:256;
	this.clusteringEnabled=($options.clusteringEnabled===false)?false:true;
	if($options.clusterMarkerClick){
		this.clusterMarkerClick=$options.clusterMarkerClick;
	}
	if($options.clusterMarkerIcon){
		this.clusterMarkerIcon=$options.clusterMarkerIcon;
	}else{
		this.clusterMarkerIcon=new GIcon();
		this.clusterMarkerIcon.image='/pu_azportal/images/maps/flag_cluster.png';
		this.clusterMarkerIcon.iconSize=new GSize(27, 35);
		this.clusterMarkerIcon.iconAnchor=new GPoint(10, 33);
		this.clusterMarkerIcon.infoWindowAnchor=new GPoint(0, 0);
		//this.clusterMarkerIcon.shadow='http://www.augsburger-allgemeine.de/pu_azportal/images/maps/shadow.png';
		//this.clusterMarkerIcon.shadowSize=new GSize(43, 33);
	}
	this.clusterMarkerTitle=($options.clusterMarkerTitle)?$options.clusterMarkerTitle:'Klicken Sie hier um den Ausschnitt zu vergrößern und %count Marker anzuzeigen';
	if($options.fitMapMaxZoom){
		this.fitMapMaxZoom=$options.fitMapMaxZoom;
	}
	this.intersectPadding=($options.intersectPadding)?$options.intersectPadding:0;
	if($options.markers){
		this.addMarkers($options.markers);
	}
	this.enabled=true;	
	GEvent.bind(this._map, 'moveend', this, this._moveEnd);
	GEvent.bind(this._map, 'zoomend', this, this._zoomEnd);
	GEvent.bind(this._map, 'maptypechanged', this, this._mapTypeChanged);
}

ClusterMarker.prototype.addMarkers=function($markers){
	var i;
	if(!$markers[0]){
		var $numArray=[];
		for(i in $markers){
			$numArray.push($markers[i]);
		}
		$markers=$numArray;
	}
	for(i=$markers.length-1; i>=0; i--){
		$markers[i]._isVisible=false;
		$markers[i]._isActive=false;
		$markers[i]._makeVisible=false;
	}
	this._mapMarkers=this._mapMarkers.concat($markers);
};

ClusterMarker.prototype._clusterMarker=function($clusterGroupIndexes){
	function $newClusterMarker($location, $icon, $title){
		return new GMarker($location, {icon:$icon, title:$title});
	}
	var $clusterGroupBounds=new GLatLngBounds(), i, $clusterMarker, $clusteredMarkers=[], $marker, $this=this, $mapMarkers=this._mapMarkers;
	for(i=$clusterGroupIndexes.length-1; i>=0; i--){
		$marker=$mapMarkers[$clusterGroupIndexes[i]];
		$marker.index=$clusterGroupIndexes[i];
		$clusterGroupBounds.extend($marker.getLatLng());
		$clusteredMarkers.push($marker);
	}
	$clusterMarker=$newClusterMarker($clusterGroupBounds.getCenter(), this.clusterMarkerIcon, this.clusterMarkerTitle.replace(/%count/gi, $clusterGroupIndexes.length));
	$clusterMarker.clusterGroupBounds=$clusterGroupBounds;	//	only req'd for default cluster marker click action
	this._eventListeners.push(GEvent.addListener($clusterMarker, 'click', function(){
		$this.clusterMarkerClick({clusterMarker:$clusterMarker, clusteredMarkers:$clusteredMarkers });
	}));
	$clusterMarker._childIndexes=$clusterGroupIndexes;
	for(i=$clusterGroupIndexes.length-1; i>=0; i--){
		$mapMarkers[$clusterGroupIndexes[i]]._parentCluster=$clusterMarker;
	}
	return $clusterMarker;
};

ClusterMarker.prototype.clusterMarkerClick=function($args){
	this._map.setCenter($args.clusterMarker.getLatLng(), this._map.getBoundsZoomLevel($args.clusterMarker.clusterGroupBounds));
};

ClusterMarker.prototype._filterActiveMapMarkers=function(){
	var $borderPadding=this.borderPadding, $mapZoomLevel=this._map.getZoom(), $mapProjection=this._map.getCurrentMapType().getProjection(), $mapPointSw, $activeAreaPointSw, $activeAreaLatLngSw, $mapPointNe, $activeAreaPointNe, $activeAreaLatLngNe, $activeAreaBounds=this._map.getBounds(), i, $marker, $uncachedIconBoundsIndexes=[], $oldState, $mapMarkers=this._mapMarkers, $iconBounds=this._iconBounds;
	if($borderPadding){
		$mapPointSw=$mapProjection.fromLatLngToPixel($activeAreaBounds.getSouthWest(), $mapZoomLevel);
		$activeAreaPointSw=new GPoint($mapPointSw.x-$borderPadding, $mapPointSw.y+$borderPadding);
		$activeAreaLatLngSw=$mapProjection.fromPixelToLatLng($activeAreaPointSw, $mapZoomLevel);
		$mapPointNe=$mapProjection.fromLatLngToPixel($activeAreaBounds.getNorthEast(), $mapZoomLevel);
		$activeAreaPointNe=new GPoint($mapPointNe.x+$borderPadding, $mapPointNe.y-$borderPadding);
		$activeAreaLatLngNe=$mapProjection.fromPixelToLatLng($activeAreaPointNe, $mapZoomLevel);
		$activeAreaBounds.extend($activeAreaLatLngSw);
		$activeAreaBounds.extend($activeAreaLatLngNe);
	}
	this._activeMarkersChanged=false;
	if(typeof($iconBounds[$mapZoomLevel])==='undefined'){
		this._iconBounds[$mapZoomLevel]=[];
		this._activeMarkersChanged=true;
		for(i=$mapMarkers.length-1; i>=0; i--){
			$marker=$mapMarkers[i];
			$marker._isActive=$activeAreaBounds.containsLatLng($marker.getLatLng())?true:false;
			$marker._makeVisible=$marker._isActive;
			if($marker._isActive){
				$uncachedIconBoundsIndexes.push(i);
			}
		}
	}else{
		for(i=$mapMarkers.length-1; i>=0; i--){
			$marker=$mapMarkers[i];
			$oldState=$marker._isActive;
			$marker._isActive=$activeAreaBounds.containsLatLng($marker.getLatLng())?true:false;
			$marker._makeVisible=$marker._isActive;
			if(!this._activeMarkersChanged && $oldState!==$marker._isActive){
				this._activeMarkersChanged=true;
			}
			if($marker._isActive && typeof($iconBounds[$mapZoomLevel][i])==='undefined'){
				$uncachedIconBoundsIndexes.push(i);
			}
		}
	}
	return $uncachedIconBoundsIndexes;
};

ClusterMarker.prototype._filterIntersectingMapMarkers=function(){
	var $clusterGroup, i, j, $mapZoomLevel=this._map.getZoom(), $mapMarkers=this._mapMarkers, $iconBounds=this._iconBounds;
	for(i=$mapMarkers.length-1; i>0; i--){
		if($mapMarkers[i]._makeVisible){
			$clusterGroup=[];
			for(j=i-1; j>=0; j--){
				if($mapMarkers[j]._makeVisible && $iconBounds[$mapZoomLevel][i].intersects($iconBounds[$mapZoomLevel][j])){
					$clusterGroup.push(j);
				}
			}
			if($clusterGroup.length!==0){
				$clusterGroup.push(i);
				for(j=$clusterGroup.length-1; j>=0; j--){
					$mapMarkers[$clusterGroup[j]]._makeVisible=false;
				}
				this._clusterMarkers.push(this._clusterMarker($clusterGroup));
			}
		}
	}
};

ClusterMarker.prototype.fitMapToMarkers=function(){
	var $mapMarkers=this._mapMarkers, $markersBounds=new GLatLngBounds(), i;
	for(i=$mapMarkers.length-1; i>=0; i--){
		$markersBounds.extend($mapMarkers[i].getLatLng());
	}
	var $fitMapToMarkersZoom=this._map.getBoundsZoomLevel($markersBounds);
	if(this.fitMapMaxZoom && $fitMapToMarkersZoom>this.fitMapMaxZoom){
		$fitMapToMarkersZoom=this.fitMapMaxZoom;
	}
	this._map.setCenter($markersBounds.getCenter(), $fitMapToMarkersZoom);
	this.refresh();
};

ClusterMarker.prototype._mapTypeChanged=function(){
	this.refresh(true);
};

ClusterMarker.prototype._moveEnd=function(){
	if(!this._cancelMoveEnd){
		this.refresh();
	}else{
		this._cancelMoveEnd=false;
	}
};

ClusterMarker.prototype._preCacheIconBounds=function($indexes, $mapZoomLevel){
	var $mapProjection=this._map.getCurrentMapType().getProjection(), i, $marker, $iconSize, $iconAnchorPoint, $iconAnchorPointOffset, $iconBoundsPointSw, $iconBoundsPointNe, $iconBoundsLatLngSw, $iconBoundsLatLngNe, $intersectPadding=this.intersectPadding, $mapMarkers=this._mapMarkers;
	for(i=$indexes.length-1; i>=0; i--){
		$marker=$mapMarkers[$indexes[i]];
		$iconSize=$marker.getIcon().iconSize;
		$iconAnchorPoint=$mapProjection.fromLatLngToPixel($marker.getLatLng(), $mapZoomLevel);
		$iconAnchorPointOffset=$marker.getIcon().iconAnchor;
		$iconBoundsPointSw=new GPoint($iconAnchorPoint.x-$iconAnchorPointOffset.x-$intersectPadding, $iconAnchorPoint.y-$iconAnchorPointOffset.y+$iconSize.height+$intersectPadding);
		$iconBoundsPointNe=new GPoint($iconAnchorPoint.x-$iconAnchorPointOffset.x+$iconSize.width+$intersectPadding, $iconAnchorPoint.y-$iconAnchorPointOffset.y-$intersectPadding);
		$iconBoundsLatLngSw=$mapProjection.fromPixelToLatLng($iconBoundsPointSw, $mapZoomLevel);
		$iconBoundsLatLngNe=$mapProjection.fromPixelToLatLng($iconBoundsPointNe, $mapZoomLevel);
		this._iconBounds[$mapZoomLevel][$indexes[i]]=new GLatLngBounds($iconBoundsLatLngSw, $iconBoundsLatLngNe);
	}
};

ClusterMarker.prototype.refresh=function($forceFullRefresh){
	if(this.enabled){
		var i, $marker, $zoomLevel=this._map.getZoom(), $uncachedIconBoundsIndexes=this._filterActiveMapMarkers();
		if(this._activeMarkersChanged || $forceFullRefresh){
			this._removeClusterMarkers();
			if(this.clusteringEnabled && $zoomLevel<this._map.getCurrentMapType().getMaximumResolution()){
				if($uncachedIconBoundsIndexes.length>0){
					this._preCacheIconBounds($uncachedIconBoundsIndexes, $zoomLevel);
				}
				this._filterIntersectingMapMarkers();
			}
			for(i=this._clusterMarkers.length-1; i>=0; i--){
				this._map.addOverlay(this._clusterMarkers[i]);
			}
			for(i=this._mapMarkers.length-1; i>=0; i--){
				$marker=this._mapMarkers[i];
				if(!$marker._isVisible && $marker._makeVisible){
					this._map.addOverlay($marker);
					$marker._isVisible=true;
				}
				if($marker._isVisible && !$marker._makeVisible){
					this._map.removeOverlay($marker);
					$marker._isVisible=false;
				}
			}
		}
	}
};

ClusterMarker.prototype._removeClusterMarkers=function(){
	var i, j, $map=this._map, $eventListeners=this._eventListeners, $clusterMarkers=this._clusterMarkers, $childIndexes, $mapMarkers=this._mapMarkers;
	for(i=$clusterMarkers.length-1; i>=0; i--){
		$childIndexes=$clusterMarkers[i]._childIndexes;
		for(j=$childIndexes.length-1; j>=0; j--){
			delete $mapMarkers[$childIndexes[j]]._parentCluster;
		}
		$map.removeOverlay($clusterMarkers[i]);
	}
	for(i=$eventListeners.length-1; i>=0; i--){
		GEvent.removeListener($eventListeners[i]);
	}
	this._clusterMarkers=[];
	this._eventListeners=[];
};

ClusterMarker.prototype.removeMarkers=function(){
	var i, $mapMarkers=this._mapMarkers, $map=this._map;
	for(i=$mapMarkers.length-1; i>=0; i--){
		if($mapMarkers[i]._isVisible){
			$map.removeOverlay($mapMarkers[i]);
		}
		delete $mapMarkers[i]._isVisible;
		delete $mapMarkers[i]._isActive;
		delete $mapMarkers[i]._makeVisible;
	}
	this._removeClusterMarkers();
	this._mapMarkers=[];
	this._iconBounds=[];
};

ClusterMarker.prototype.triggerClick=function($index){
	var $marker=this._mapMarkers[$index];
	if($marker._isVisible){
		GEvent.trigger($marker, 'click');
	}
	else if($marker._isActive){
		var $intersectingMarkerIndexes=$marker._parentCluster._childIndexes, $intersectDetected, $uncachedIconBoundsIndexes, i, j, $mapZoomLevel=this._map.getZoom();
		do{
			$intersectDetected=false;
			$mapZoomLevel++;
			if(typeof(this._iconBounds[$mapZoomLevel])==='undefined'){
				this._iconBounds[$mapZoomLevel]=[];
				this._preCacheIconBounds($intersectingMarkerIndexes, $mapZoomLevel);
			}else{
				$uncachedIconBoundsIndexes=[];
				for(j=$intersectingMarkerIndexes.length-1; j>=0; j--){
					if(typeof(this._iconBounds[$mapZoomLevel][$intersectingMarkerIndexes[j]]==='undefined')){
						$uncachedIconBoundsIndexes.push($intersectingMarkerIndexes[j]);
					}
				}
				if($uncachedIconBoundsIndexes.length>=1){
					this._preCacheIconBounds($uncachedIconBoundsIndexes, $mapZoomLevel);
				}
			}
			for(i=$intersectingMarkerIndexes.length-1; i>=0; i--){
				if($intersectingMarkerIndexes[i]!==$index && this._iconBounds[$mapZoomLevel][$intersectingMarkerIndexes[i]].intersects(this._iconBounds[$mapZoomLevel][$index])){	//	don't check that clustered marker intersects itself
					$intersectDetected=true;
					break;
				}
			}
		}
		while($intersectDetected && $mapZoomLevel<this._map.getCurrentMapType().getMaximumResolution());
		this._map.setCenter($marker.getLatLng(), $mapZoomLevel);
		this.triggerClick($index);
	}else{
		this._map.setCenter($marker.getLatLng());
		this.triggerClick($index);
	}
};

ClusterMarker.prototype._zoomEnd=function(){
	this._cancelMoveEnd=true;
	this.refresh(true);
};

ClusterMarker.prototype.enable=function(bool){
	if(bool && !this.enabled){
		this.enabled=true;
		this.refresh();
	} else if(!bool && this.enabled){
		this.enabled=false;
		this._removeClusterMarkers();
		for(var i=this._mapMarkers.length-1; i>=0; i--){
			$marker=this._mapMarkers[i];
			$marker._isActive=false;
			if($marker._isVisible){
				this._map.removeOverlay($marker);
				$marker._isVisible=false;
			}
		}
	}
};

function newMarker(markerLocation, markerId, markerDescription, markerIcon){
	var marker=new GMarker(markerLocation, { icon:markerIcon });
	GEvent.addListener(marker, 'click', function() {
		marker.openInfoWindowHtml('<p>' + markerDescription + '</p>');
	});
	return marker;
}