MapnikGetTileUrl = function (a,b,c) {
    //var tile_size = 256;
    //var p0 = new GPoint(a.x * tile_size,(a.y + 1) * tile_size);
    //var p1 = new GPoint((a.x + 1)* tile_size, a.y * tile_size);
    
    //var UL = G_NORMAL_MAP.getProjection().fromPixelToLatLng(p0,b,c);
    //var LR = G_NORMAL_MAP.getProjection().fromPixelToLatLng(p1,b,c);
    
    var url = this.myBaseURL + "/mapnik_tiles/" + b + "/" + a.x + "/" + a.y + ".png";
    
    return url;  
}