[mapserver-users] mapserver wms: srs problem

Barend Kobben kobben at itc.nl
Tue Jun 10 12:26:06 EDT 2008


Hi,

It looks like your mixing up several things that shouldn't be mixed:

1) 
http://localhost/cgi-bin/mapserv.exe?map=C:\ms4w\Apache\htdocs\ol\wms.map&SE
RVICE=WMS&VERSION=1.1.1&REQUEST=GetCapabilities
...is a valid WMS GetCapabilities request. It might result in a valid WMS
response (although I cannot test this as I obviously  do not have the same
localhost as you...)

However:  
http://localhost/cgi-bin/mapserv.exe?map=C:\ms4w\Apache\htdocs\ol\wms.map&mo
de=map
...is a non-WMS request, it uses the 'old' MapServer CGI mode, not the OGC
standardised WMS interface. To get a map the "WMS way" you'd request
something like:
http://localhost/cgi-bin/mapserv.exe?map=C:\ms4w\Apache\htdocs\ol\wms.map&m&
SERVICE=WMS&VERSION=1.1.1&REQUEST=GetMap&STYLES=&LAYERS=aLayer&BBOX=1,2,3,4&
SRS=EPSG:4326&format=image/gif

2) next, you advertise your data to be in lat-lon on the WGS 84 (PROJECTION
init=epsg:4326), but you proclaim the EXTENT of the data to be in meters or
some other projected unit:
EXTENT      184056.505 4809728.25 767381.245 5478975.75
This obviously are not lat-lon degrees (which have a max extent of
-180,180,-90,90)... Now MS will be really confused! "Hmmmm, this client
wants lat-lon data that stretches over the whole of the universe..." :-)

3) you then advertise the WMS to be able to deliver data in a non-projected
and a projected SRS:
 "wms_srs"             "EPSG:4326 EPSG:26915"
Which is fine, but you do it again for the LAYER, which I think is
superfluous.

4) You do NOT tell the WMS what SRS the data originally is in. There is no
PROJECTION object in the LAYER, which in some case might lead to MapServer
trying to find out for itself, BUT NOT in the Postgis case you have. A
connection to PostGIS in itself needs to be told which projection to fetch
the data in (because PosGIS can reproject if necessary). One of the ways of
doing that is to make the DATA statement a bit more elaborate than
  "the_geom from shp_state", instead use
 DATA   "the_geom from shp_state using unique <your_primary_key> using
srid=26915"

Hope this helps...

-- 
Barend Köbben
International Institute for Geo-Information
Sciences and Earth Observation (ITC)
PO Box 6
7500AA Enschede, The Netherlands
+31 (0)53 4874253

International Institute for Geo-Information Science and Earth Observation (ITC)
Chamber of Commerce: 410 27 560

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