[OpenLayers-Users] epsg:3857 and google 900913

[Arnd Wippermann]

Hi Caspar,
 
"In other words, it will only use the map projection in it's WMS request
URL's"
 
That's not right as you have found out by yourself. If the map projection is
equal the wms projection, then the WMS GetMap Request use the wms
projection.
 
Some servers provide only requests for EPSG:3857 (an alias for EPSG:900913)
and if you use for your map EPSG:900913, then you can add these servers and
set the projection to EPSG:3857 and it works.
 
But it seems, that that only works for EPSG:900913 and EPSG:4326 and their
aliases, because OpenLayers has aliases defined in OpenLayers Projection.js.
 
If you have maps with other projections and a server support only an alias
of the projection, then the above will perhaps not work.
 
Then the only way is to overwrite the getFullRequestString-method of
OpenLayers.Layer.WMS.
 
Example
http://gis.ibbeck.de/ginfo/apps/OLExamples/OL212/wms_options_projection.asp
 
Arnd


  _____  

Von: openlayers-users-bounces at lists.osgeo.org
[mailto:openlayers-users-bounces at lists.osgeo.org] Im Auftrag von Casper Span
Gesendet: Mittwoch, 16. Januar 2013 12:53
An: Sergeant_york
Cc: openlayers-users at lists.osgeo.org
Betreff: Re: [OpenLayers-Users] epsg:3857 and google 900913


Hi,


If you look at the source of WMS (lib\OpenLayers\Layer\WMS.js), take a look
at getFullRequestString.

In it, the baselayer's projection will always override the given projection.
In fact, the layers projection itself will be ignored:

- It takes the Map Projection (=Baselayer projection)

- then, if the WMS layer projection equals the map projection, it uses the
layer projection

- otherwise, it uses the map projection


In other words, it will only use the map projection in it's WMS request
URL's


So yeah... everything MUST be the same projection for WMS layers or it
cannot be placed on top of eachother.

For me, this meant reprojecting my own data so I can serve it with WMS onto
OSM.


You can check these actual outgoing URL's with Firebug and such.


regards,

Casper Span


On Wed, Jan 16, 2013 at 12:31 PM, Sergeant_york <electronicpanda at gmail.com>
wrote:


Hello there,

Thank you for the answer. That gave me a good idea. Unfortunately it doesn't
work when initializing layer.

On the other hand creating a layer (for example aLayer object) then changing
projection works!

Workin way is:
layer aLayer=new OpenLayers.Layer.WMS ......
aLayer.projection= new OpenLayers.Projection("EPSG:3857")



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Casper Span
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M: info at spatially-oriented.com


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