[OpenLayers-Dev] Strange behaviour in Layer.XYZ

[Robert Sanson]

Tiles I request from an ArcGIS Server tile cache using Layer.XYZ are not lining up with other layers requested from the same server via Layer.WMS or Layer.ArcGIS93Rest. 
 
Here is my code snippet:
 
var mapoptions = {
  //tileOrigin: new OpenLayers.LonLat(-4020900,19998100), //Origin as reported by ArcGIS
    maxExtent: new OpenLayers.Bounds(-4020900, 4674128.11975, 2568710.79993, 19998100), //contains the AGS origin
    restrictedExtent: new OpenLayers.Bounds(1018697.71047, 4674128.11975, 2568710.79993, 6296981.53325),
    resolutions: new Array(3175.0063500127, 793.751587503175, 264.583862501058, 198.437896875794, 132.291931250529, 66.1459656252646, 26.4583862501058, 19.8437896875794, 13.2291931250529, 9.26043518753704, 6.61459656252646, 5.29167725002117, 3.96875793751588, 2.64583862501058, 1.98437896875794, 1.32291931250529),
    tileSize: new OpenLayers.Size(256,256),
    units: 'm',
    projection: new OpenLayers.Projection('EPSG:2193'),
    fractionalZoom: false
};
var map = new OpenLayers.Map( 'map',mapoptions );
var nzcoastwms = new OpenLayers.Layer.WMS( "Coastline",
                          "http://ws-esrimt/arcgis/services/mapservice_asurequality_prod/MapServer/WMSServer",
                          {layers: ['0'], format: "image/png"},
                          {isBaseLayer: true, singleTile:true, visibility: true,
                           attribution:"LINZ data Crown copyright reserved"} );
var topoxyz = new OpenLayers.Layer.XYZ( "Topo",
                    "http://ws-esrimt/ArcGIS/rest/services/mapservice_topography_vector_prod/MapServer/tile/${z}/${y}/${x}",
                   {isBaseLayer: false, sphericalMercator: false//, tileOrigin: new OpenLayers.LonLat(-4020900,19998100)
});
map.addLayers([nzcoastwms,topoxyz]);

Doing this above, requests the correct tiles, but it seems the requested tiles are displaced in a north-south direction, depending on Zoom level. I have previously verified the WMS layer is in the correct location. All the data and the map are in NZ Transverse Mercator (EPSG:2193), so there is no projection.
 
Here are some numbers to show the problem based on relative locations of the same features on the map:
Layer zoom res pixel.x pixel.y x y relative px relative y (m) displacement
WMS 0 3175.00635 328 207 2022304.713 5641130.138   
XYZ 0 3175.00635 328 168 2022304.713 5764955.385 -39 123825.25 North
 
WMS 1 793.7515875 219 265 1764335.447 5478411.062   
XYZ 1 793.7515875 219 370 1764335.447 5395067.146 105 -83343.92 South
 
WMS 2 264.5838625 148 284 1765129.198 5478146.478   
XYZ 2 264.5838625 148 344 1765129.198 5462271.447 60 -15875.03 South
 
WMS 3 198.4378969 97 289 1762152.63 5479006.376   
XYZ 3 198.4378969 97 199 1762152.63 5496865.787 -90 17859.41 North
 
WMS 4 132.2919313 155 235 1762218.776 5479204.814   
XYZ 4 132.2919313 155 358 1762218.776 5462932.906 123 -16271.91 South
 
WMS 5 66.14596563 121 273 1757522.412 5473317.823   
XYZ 5 66.14596563 121 262 1757522.412 5473979.283 -11 661.46 North
 
WMS 6 26.45838625 103 307 1757509.183 5473317.823   
XYZ 6 26.45838625 103 408 1757509.183 5470645.526 101 -2672.30 South
 
Is this a bug?
 
Thanks,
 
Robert Sanson


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