[OpenLayers-Dev] [OpenLayers-Users] ArcGIS Server map cache and OpenLayers

Mike Adair madair at dmsolutions.ca
Fri Dec 7 09:02:51 EST 2007

We had to implement an override of the Layer.Grid.initGriddedTiles  
method for the MapGuide Layer since the tile origin for MGOS is 
upper-left.  (See 
That could easily be implemented using an option on the Layer.


>> Is it possible to specify a origin/upper-left position of just one
>> grid/tile layer without affecting the other layers that work correctly?
>> Since I know the tile origin of the AGS map cache, I would like to
>> shift the AGS layer so that the first image loaded starts at that
>> position (geographically correct) and not where the WMS tiles are
>> starting from.<br>
> You would need to add this functionality to the Layer.Grid class. Tim
> Schaub has done some work on this -- I don't know if he has any code --
> but essentially, the Layer.Grid class should accept a 'TileOrigin' which
> would allow you to state from where the tiles are centered.
> Currently, the way you do this is by setting the maxExtent of the layer.
> If you set the maxExtent of the layer to the extent of your ArcGIS
> cache, it *should* work. 
> For the record, most OL code is based on the lower left, rather than
> upper right, corner. This is probably going to be useful to know for any
> development you do.

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