OpenLayers - TileStache Overlay: tiles loaded but not visible

Question

I have been trying this since yesterday. If I load only the tilestache layer, it is visible. If I load both bing and tilestache layer, the tilestache layer is not visible. When I look at the firebug console, the tiles are being loaded.

_map = new OpenLayers.Map({div: 'map'});
bing = new OpenLayers.Layer.Bing({
    key: 'AqR9gcXm14-PKVQsWrL8H9A_RnusHZCzQKX_tbJegzU1EOZGafcjzCYbcpkwukQh',
    type: 'Aerial'
});

tilestache = new OpenLayers.Layer.XYZ(
        'hul',
        'http://www.hyderabadurbanlab.com/tiles/tiles.py/hul2/${z}/${x}/${y}.png',
        {
          tileSize: new OpenLayers.Size(256, 256),
          tileOrigin: get_point(17.4099, 78.4761),
          sphericalMercator: true,
          isBaseLayer: false,
          transparent: true,
          opacity: 0.6,
          transitionEffect: 'resizing',
          buffer: 1,
          wrapDateLine: true
        }
    );
_map.addLayers([bing, tilestache]);

Attached is the screen shot of how it looks.

When I load just the tilestache layer, it looks like this:

I want the Bing maps as the base layer and the tilestache layer on top of it as an overlay.

Thank you.

Answer 1

When I set a value of 1 to the zoomOffset, the tilestache layer is visible.

Bing maps zoom levels start with 0. Looks like the tiles layer (like google) starts with 1. By giving a proper offset, tiles of the required zoom level are being requested and shown.

Answer 2

i think the problem you have mentioned that stem from projection settings. check out your map and layers projections.

var geographic = new OpenLayers.Projection("EPSG:4326");
var mercator = new OpenLayers.Projection("EPSG:900913");

or test it with sphericalMercator = false;

i hope it helps you...