function switchlayer (layername,layername2) 
{
// turn off all layers
$('layer_1').hide();
$('layer_2').hide();

//turn on layer you want to display
$(layername).show();

if ( $('mapControl') ) {
	var offsets = Position.cumulativeOffset($('myMap'));
	$('mapControl').style.left = offsets[0]+10+'px';
	$('mapControl').style.top = offsets[1]+10+'px';	
}

}