docs: function(bounds, origin, resolution) {
          var tilelon = resolution*this.tileSize.w;
          var tilelat = resolution*this.tileSize.h;
          
          var offsetlon = bounds.left;
          var tilecol = Math.floor(offsetlon/tilelon) - this.buffer;
          
          var offsetlat = bounds.top;  
          var tilerow = Math.floor(offsetlat/tilelat) + this.buffer;
          
          return { 
            tilelon: tilelon, tilelat: tilelat,
            startcol: tilecol, startrow: tilerow
          };
      }