code: function (bounds) {
          bounds = this.adjustBounds(bounds);
          var res = this.getServerResolution();
          var x = Math.round((bounds.left - this.tileOrigin.lon) / (res * this.tileSize.w));
          var y = Math.round((this.tileOrigin.lat - bounds.top) / (res * this.tileSize.h));
          var z = this.getZoomForResolution( res );
  
          var tileIndex = x + y * this.tierSizeInTiles[z].w + this.tileCountUpToTier[z];
          var path = "TileGroup" + Math.floor( (tileIndex) / 256 ) +
              "/" + z + "-" + x + "-" + y + ".jpg";
          var url = this.url;
          if (OpenLayers.Util.isArray(url)) {
              url = this.selectUrl(path, url);
          }
          return url + path;
      }
docs: Method: getURL
  
  Parameters:
  bounds - {<OpenLayers.Bounds>}
  
  Returns:
  {String} A string with the layer's url and parameters and also the
  passed-in bounds and appropriate tile size specified as
  parameters