var imag = new Array(7);

     imag[0] = "img/DUNAS-cero_uso_map.gif";
	 imag[1] = "img/DUNAS-par_ton_map.gif";
	 imag[2] = "img/DUNAS-sen_map.gif";
	 imag[3] = "img/DUNAS-apa_map.gif";
	 imag[4] = "img/DUNAS-miradores_map.gif";
	 imag[5] = "img/DUNAS-cen_int_map.gif";
	 imag[6] = "img/DUNAS-bus_map.gif";
	 imag[7] = "img/DUNAS-ser_pla_map.gif";
	 imag[8] = "img/DUNAS-lit_map.gif";
	
  for (i=0; i <  imag.length; i++) {
    var preload = new Image();
    preload.src =  imag[i];
  }

  function usos(imgIndex, imgTarget) {
   document[imgTarget].src =  imag[imgIndex];
 }