code: function(lon, lat) {
          if ( (lon == null) || (lat == null) ) {
              throw new TypeError('LonLat.add cannot receive null values');
          }
          return new OpenLayers.LonLat(this.lon + OpenLayers.Util.toFloat(lon), 
                                       this.lat + OpenLayers.Util.toFloat(lat));
      }
docs: APIMethod: add
  
  Parameters:
  lon - {Float}
  lat - {Float}
  
  Returns:
  {<OpenLayers.LonLat>} A new OpenLayers.LonLat object with the lon and
  lat passed-in added to this's.