[OpenLayers-Users] WMS and Mercator projection

[David Fawcett]

JOSM does not run in a Web browser...



On Jun 1, 2010, at 5:51 AM, Joosep-Georg Järvemaa <openlayers+users at nonsense.e 
e> wrote:

> 2010/6/1 Andreas Hocevar <ahocevar at opengeo.org>:
>>>>>
>>> So you're saying that this JOSM-like behaviour where I have the
>>> display picture in EPSG:3857 and am working with real coordinates is
>>> not possible at all with OpenLayers?
>>
>> Exactly. This is why I showed you the other approach - requesting  
>> the tiles in the appropriate projection.
>>
>> In general, reprojecting images on the client needs processing  
>> power. Browsers don't have a lot of that.
>
> Well, it's just beyond my understanding how can JOSM do that and why
> can OpenLayers not -- only thing what has to be done is ask the image
> from the WMS server -- and the server already serves the image in
> right projection what I want to see.
>
> The link I'm dragging along is not constructed by myself but is a real
> working URI grabbed from JOSM debug output --
> http://xgis.maaamet.ee/wms-pub/alus-geo?STYLES=&SRS=EPSG:4326&FORMAT=image/png&VERSION=1.1.1&REQUEST=GetMap&LAYERS=of10000,TOPOYKSUS_6569,TOPOYKSUS_7793&bbox=24.6461274,59.3624859,24.6479219,59.3634004&width=499&height=499
>
> And looking at all those Mercator-examples for OpenLayers something
> tells me that it must be possible... Google serves images in Mercator,
> right? So does the server at maaamet.ee -- you just have to ask for
> the image with EPSG:4326 and real coordinates.
>
> How hard can be translating coordinates from one EPSG to another? Some
> OpenLayers examples show some coordinates-translation being done... I
> just can not understand how can JOSM have that "computing power" and
> browser running on very same machine suddenly does not.
>
>
> My final goal is to start drawing vector data from OSM on that
> maaamet.ee WMS layer.
>
> I just would like to accomplish that without starting to write my own
> JavaScript library which would do that because I am not familiar with
> GIS internals that much...
>
>
>
> Regards,
> -- 
> Joosep-Georg
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