[mapguide-users] WMS Consumption and Coordinate Transformation

Andy Morsell amorsell at spatialgis.com
Tue Feb 12 14:51:57 EST 2008


I am trying to straighten this out since I am fairly confused about MapGuide
and WMS coordinate transformations.  There have been many discussions in the
past about this, some of which I've been part of, but most pertain to the
SERVING of WMS layers rather than consuming them.

In this case, I need to consume a WMS layer published in EPSG:4326 and have
it displayed in a MGOS or MGE map using EPSG 2914.  In Studio, the
datasource works fine, and the layer displays fine using 4326.  In turn, a
4326 map displays the layer fine, but a map in any other coordinate system
will not display the WMS layer data.

Exactly how does how this happen on the back-end of MGOS since one cannot
specify a coordinate system for a WMS datasource?  Is it supposed  to look
up the EPSG code from the maps assigned coordinate system code and then
incorporate that (and the bounding box info) into the WMS request?  Is there
any way to find out what WMS requests are actually being formed for
trouble-shooting purposes?  

I know that the EPSG code exists on the server as I am able to use the
ConvertEpsgCodetoWkt via the mapagent.  The server in question is an ER
Mapper server and I saw a reference to MGOS URL encoding the WMS requests
and that this is supposed to be fixed in R2.  However, I tested with version
2 RC2 and see the same problems.

Issuing the WMS requests within a browser (or via Gaia) works just fine with
different EPSG codes.

http://wms.oregonexplorer.info/ImageX/ecw_wms.dll?REQUEST=GetMap&SERVICE=WMS
&VERSION=1.1.1&LAYERS=2005ORTHOIMAGERY.ECW&STYLES=&FORMAT=image/png&BGCOLOR=
0xFFFFFF&TRANSPARENT=TRUE&SRS=EPSG:4326&BBOX=-124.5666667,40.6839378963289,-
116.428612945493,47.5664062144262&WIDTH=875&HEIGHT=740

http://wms.oregonexplorer.info/ImageX/ecw_wms.dll?REQUEST=GetMap&SERVICE=WMS
&VERSION=1.1.1&LAYERS=2005ORTHOIMAGERY.ECW&STYLES=&FORMAT=image/png&BGCOLOR=
0xFFFFFF&TRANSPARENT=TRUE&SRS=EPSG:2914&BBOX=3814657.887703,-27439.929517068
7,6029145.271766,1845383.68671907&WIDTH=875&HEIGHT=740

Any help or explainations would be appreciated.  Thank you very much.

Andy Morsell, P.E.
Spatial Integrators, Inc.
http://www.SpatialGIS.com

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