function setZoomWidthQuarter(){
  var zoomwidth;
  var zoomwidthQuarter;
  // rounding to two decimal places
  zoomwidth= Math.round( (getZoomWidth().value/4.0) *100) / 100 ;
  //alert("setZoomWidthQuarter " +getZoomWidth());
  try{

    zoomwidthQuarter = document.getElementById('zoomWidthMilesQuarter');
	zoomwidthQuarter.value= zoomwidth ;

    
  } catch(err){alert('getZoomWidthQuarter is not available');}

}