 				validateSpatialIndex();
 			
 			// draw plot
-			if (!PlotterUtils.bitmapDataIsEmpty(plotBitmap))
-			{
-				PlotterUtils.clear(plotBitmap.bitmapData);
+			if (!PlotterUtils.bitmapDataIsEmpty(_plotBitmap))
+			{
+				PlotterUtils.clear(_plotBitmap.bitmapData);
 				// get keys for plot, then draw the records
 				
 				if (shouldDraw)
 				{
 					if (!isOverlay.value)
-						plotter.drawBackground(_dataBounds, _screenBounds, plotBitmap.bitmapData);
+						plotter.drawBackground(_dataBounds, _screenBounds, _plotBitmap.bitmapData);
 					
 					var keys:Array = getSelectedKeys() || []; // use empty Array if keys are null
-					plotter.drawPlot(keys, _dataBounds, _screenBounds, plotBitmap.bitmapData);
+					plotter.drawPlot(keys, _dataBounds, _screenBounds, _plotBitmap.bitmapData);
 				}
 			}
 			//trace(name,'end updateDisplayList', _dataBounds);

		{
			//trace("sizeChanged",unscaledWidth,unscaledHeight);
			
			var bitmapChanged:Boolean = PlotterUtils.setBitmapDataSize(plotBitmap, unscaledWidth, unscaledHeight);
			if (bitmapChanged)
				invalidateDisplayList();
		}

		{
			// clean up everything that does not get cleaned up automatically.
			disposeObjects(
				_plotBitmap.bitmapData
			);
			if (!usingExternalSpatialIndex)
				disposeObjects(spatialIndex);
