[OpenLayers-Dev] RE: WMS request mod

ray.diciaccio ray.diciaccio at ll.mit.edu
Fri May 20 11:05:21 EDT 2011

Ok, so it sounds to me like the "right" way to do this would be to follow
Bob's suggestion and use some middleware piece to do the reprojection --
that way I wouldn't need to worry about the distortion?

- Ray

Dominik Mikiewicz wrote:
> Yeah, I should have added - large scales are fine (> 1m, 500k), small are
> distorted.
> -----Original Message-----
> From: andreas.hocevar at gmail.com [mailto:andreas.hocevar at gmail.com] On
> Behalf
> Of Andreas Hocevar
> Sent: Friday, May 20, 2011 9:26 AM
> To: Dominik Mikiewicz
> Cc: Ray Di Ciaccio; openlayers-dev at lists.osgeo.org
> Subject: Re: [OpenLayers-Dev] WMS request mod
> This approach will only work well for tiles that are near the equator,
> or don't span over a wide range of latitudes. It is basically the same
> thing that happens when you use the not recommended reproject: true
> option for Layer.WMS.
> Andreas.
> On Fri, May 20, 2011 at 8:54 AM, Dominik Mikiewicz
> <dominikmikiewicz at o2.pl> wrote:
>> This should work just fine. There won't be a serious performance hit
> either as you only recalculate bbox and change srs on the clientside. I do
> it quite often and even extended a wms layer class so I can quickly set up
> my 4326 layers to work with spherical Mercator.
>> However you may experience some issues with tile caching as sometimes the
> precision may vary from browser to browser. Another thing is the
> getFeatureInfo request - make sure you send correct cords if you are going
> to use it.
>> dom
>> -----Original Message-----
>> From: openlayers-dev-bounces at lists.osgeo.org
> [mailto:openlayers-dev-bounces at lists.osgeo.org] On Behalf Of Ray Di
> Ciaccio
>> Sent: Thursday, May 19, 2011 6:00 PM
>> To: openlayers-dev at lists.osgeo.org
>> Subject: [OpenLayers-Dev] WMS request mod
>> Sorry for the previous messed up message. Let me try this again:
>> Hi all,
>> I'm in what I'm guessing is a fairly common situation -- I'm using
>> Google Maps as my baselayer (so map is in EPSG:9009l3 projection) and
>> I'm trying to load an overlay from a WMS which I have no control over.
>> It only offers data in EPSG:4326. The WMS request generated by
>> OpenLayers will be for CRS=EPSG:900913 and the BBOX values will be in
>> EPSG:900913. This obviously won't work if the WMS only offers EPSG:4326.
>> My solution to this problem was to override
>> OpenLayers.Layer.WMS.getFullRequestString() so that it uses the
>> projection that I set for that particular layer -- it changes the
>> CRS/SRS param to whatever the layer projection is, and it transforms the
>> BBOX values from the map projection to the layer's projection. This way
>> I get a valid request for the WMS and it's loaded in the correct
>> location on the basemap. My question is whether this is the right
>> approach to this situation and whether there may be unforeseen
>> repercussions to these changes I made.
>> Thanks!
>> - Ray
>> --
>> Ray Di Ciaccio
>> MIT LL, Group 42
>> 781-981-2024
>> ray.diciaccio at ll.mit.edu
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> -- 
> Andreas Hocevar
> OpenGeo - http://opengeo.org/
> Expert service straight from the developers.
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