Hi,
Have a look at the capabilities of this tiled WMS server
http://maps.gns.cri.nz/geoserver/wms?service=wms&version=1.1.1&request=getcapabilities&tiled=true
You will find this:
<TileSet>
<SRS>EPSG:900913</SRS>
<BoundingBox SRS="EPSG:900913" minx="-2.003750834E7"
miny="-2.003750834E7" maxx="2.0037508345578495E7" maxy="2.0037508345578495E7"/>
<Resolutions>156543.033928041 78271.51696402048 39135.75848201023
19567.87924100512 9783.93962050256 4891.96981025128 2445.98490512564
1222.99245256282 611.49622628141 305.7481131407048 152.8740565703525
76.43702828517624 38.21851414258813 19.10925707129406 9.554628535647032
4.777314267823516 2.388657133911758 1.194328566955879 0.5971642834779395
</Resolutions>
<Width>256</Width>
<Height>256</Height>
<Format>image/png</Format>
<Layers>gns:PETROLEUM.IWI_BOUNDARIES</Layers>
<Styles/>
</TileSet>
It means that if you ask for a tiled output with TILED=TRUE, you can only get a
ready defined tile with fixed scale, fixed size, and fixed location. On the
other hand, standard WMS is sending you exactly what you ask with BBOX and
WIDTH and HEIGHT.
With this nice application on MapTiler page you can see the tiles. At some
zoom layer, somewhere in the world, you should be able to see the same tile
that you get from Geoserver with that TILED=TRUE request.
http://www.maptiler.org/google-maps-coordinates-tile-bounds-projection/
In order to get exactly same image with and without TILED=TRUE the standard WMS
call must use WIDTH and HEIGHT that are the same than the tile size, 256 x 256
in this case, but also a BBOX that is exactly the same than tile boundaries.
You can click tiles with the Maptiler application, copy the tile boundaries
from the pop-up, copy them to BBOX in the non-tiling WMS GetMap and then (and
only then) the result should match output of the TILED=TRUE request.
I have not checked if your BBOX is matching one of the 900913 tiles. If it
does and you still get back an image covering a bit different area I do not
know what happens.
-Jukka Rahkonen-
Phil Scadden wrote:
>
> These URLs are on a public geoserver.
>
> This one opens directly in the browser.
> http://maps.gns.cri.nz/geoserver/wms?LAYERS=gns%3APETROLEUM.IWI_B
> OUNDARIES&FORMAT=image%2Fpng&TRANSPARENT=TRUE&SERVICE=WM
> S&VERSION=1.1.1&REQUEST=GetMap&STYLES=&SRS=EPSG%3A900913&BBO
> X=18785164.06875,-4642705.18625,19411336.204375,-
> 4016533.050625&WIDTH=256&HEIGHT=256
>
>
> This one is identical except for the TILED=TRUE (so goes to GWC which is on,
> with WMS integration). The tile origin parameter makes no difference
> whether present or not. Also oddly, the returned header is such that the
> browser wants to save to file.
> http://maps.gns.cri.nz/geoserver/wms?LAYERS=gns%3APETROLEUM.IWI_B
> OUNDARIES&FORMAT=image%2Fpng&TILED=TRUE&TILESORIGIN=-
> 20037508.34%2C-
> 20037508.34&TRANSPARENT=TRUE&SERVICE=WMS&VERSION=1.1.1&REQUE
> ST=GetMap&STYLES=&SRS=EPSG%3A900913&BBOX=18785164.06875,-
> 4642705.18625,19411336.204375,-4016533.050625&WIDTH=256&HEIGHT=256
>
> This is some odd going with OpenLayers as well, but it is hard to figure out
> until I can understand why geoserver returns different images. I would
> expect them to be identical.
>
> --
> Phil Scadden, GNS Science Ltd 764 Cumberland St, Private Bag 1930, Dunedin,
> New Zealand Ph +64 3 4799663, fax +64 3 477 5232
>
> Notice: This email and any attachments are confidential. If received in error
> please destroy and immediately notify us. Do not copy or disclose the
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