function init() {
	zoom = overlay.style; 
	bgmap = basemap.style;
}

function displayOverlay(e) {
   // check that the page has loaded
	if (typeof(zoom) == "undefined")
	   return;
	var mx = window.event.offsetX; 
	var my = window.event.offsetY;
	var buffer = 70;
	zoom.visibility = "visible";	
	zoom.left = 0; 
	zoom.top = 0;
	zoom.clip = "rect(" + (my-buffer) +" "+ (mx+buffer) +" "+ (my+buffer) +" "+ (mx-buffer) +")";
}

function clearOverlay(e) {
	if (typeof(zoom) == "undefined")
	   return;
   zoom.visibility ="hidden";
}