function getMapName(urlString) {
  //get filename
  var s = urlString.substring( urlString.lastIndexOf('/')+1 );
  //get current map identifier
  var s = s.substring( 0, s.indexOf('-') );
  return s;
}


function setAction(f) {

  //get url-path portion of url
  var mapName = getMapName(location.pathname);
  //get selected value from dropdown
  var day = f.elements[0].options[f.elements[0].selectedIndex].value;

  
  //build url to go to and set form action
  f.action = mapName+'-'+day+'.html';
  
  return true;
}