WMS and SRS
Daniel Goetz
madprof at GMX.CH
Fri Jul 28 07:16:40 EDT 2006
Hi Bart,
thanks again.
I put the images (including parameters of the reequests) on a website. Just follow this link: http://www.toe-net.de/WMS_SRS.html
Perhaps now you can better understand what I mean and perhaps you have a solution for my problems.
Thank you so much for your time, your thoughts and your ideas. Thank you.
regards
Daniel
-------- Original-Nachricht --------
Datum: Fri, 28 Jul 2006 11:21:43 +0200
Von: "Bart van den Eijnden (OSGIS)" <bartvde at XS4ALL.NL>
An: MAPSERVER-USERS at LISTS.UMN.EDU
Betreff: Re: [UMN_MAPSERVER-USERS] WMS and SRS
> Hi Daniel,
>
> you are right, SIZE is equivalent to WIDTH/HEIGHT in WMS. And EXTENT is
> equivalent to BBOX.
>
> Are you able to send us some screendumps of what you are experiencing?
> Or put them on a website and send the links?
>
> Best regards,
> Bart
>
> Daniel Goetz wrote:
>
> >Hi Bart,
> >
> >thank you again for your help.
> >
> >I am sorry, but I think because of my limited skills in writing in
> english you have misunderstood what I wanted to say. Sorry for that.
> >
> >I meant in my last email that the EXTENT in a mode=browse ("normal"
> mapserver CGI request) is the equivalent to the BBOX-values in the
> WMS-GetMap-request. And that SIZE in "normal" mapserver request is equivalent to
> WIDTH/HEIGHT in WMS-GetMap-requests. Am I right? And the EXTENT-values and the
> BBOX-values did not alter; neither in the WMS-request nor in the "normal"
> mode=browse CGI mapserver-request. Same with SIZE and WIDTH/HEIGHT. And
> nevertheless these values did not alter in the two different requests, the
> returened reprojected maps differ (stretching).
> >
> >
> >
> >
> >
> >>I think the stretching behaviour (non square pixels) is specific to WMS
> >>and won't happen in Mapserver CGI mode.
> >>
> >>
> >
> >It is the map of the "normal" mode=browse mapserver-request that seems to
> be stretched compared to the not reprojected map. The reprojected map of
> the WMS-GetMap-request looks similar/equal to the not reprojected map.
> >
> >But isn't it quiet normal that reprocetion causes some kind of stretching
> and distortion? Please correct me if I am wrong.
> >
> >
> >So thank you for your reply. And sorry for my bad english/description of
> my problems. Thank you for furhter support in advance.
> >
> >
> >
> >regards
> >
> >
> >Daniel
> >
> >
> >
> >-------- Original-Nachricht --------
> >Datum: Fri, 28 Jul 2006 10:52:39 +0200
> >Von: "Bart van den Eijnden (OSGIS)" <bartvde at xs4all.nl>
> >An: Daniel Goetz <madprof at GMX.CH>
> >Betreff: Re: [UMN_MAPSERVER-USERS] WMS and SRS
> >
> >
> >
> >>Hi Daniel,
> >>
> >>I think the stretching behaviour (non square pixels) is specific to WMS
> >>and won't happen in Mapserver CGI mode.
> >>
> >>For WMS, the SIZE and EXTENT of the MAP file don't matter, since they
> >>are specified in the request.
> >>
> >>The easiest is to test with a square image. So eg 400 x 400 pixels.
> >>
> >>Then make sure that MAXX-MINX equals MAXY-MINY
> (BBOX=MINX,MINY,MAXX,MAXY).
> >>
> >>Best regards,
> >>Bart
> >>
> >>Daniel Goetz wrote:
> >>
> >>
> >>
> >>>Hi Bart,
> >>>
> >>>thank you for your reply.
> >>>
> >>>But the extent in the mapfile is the same as the BBOX-values in the
> >>>
> >>>
> >>WMS-request. And the SIZE in the MAP-object of the mapfile is the same
> as in
> >>WIDTH+HEIGHT in the WMS-request. And nevertheless the two "reprojected"
> maps
> >>differ in appearance (distortion).
> >>
> >>
> >>>But you are right. I should check that the BBOX and the
> >>>
> >>>
> >>WIDTH/HEIGHT-values have the same proportion. Do I also have to check
> wheter SIZE and EXTENT
> >>in the MAP-object have the same proportions as well? And how can I
> measure
> >>the distance between the vertices of my EXTENT and the distance between
> >>the vertices of my BBOX? Any suggestion?
> >>
> >>
> >>>Thank you for your help and hopefully your further ideas. Thank you.
> >>>
> >>>
> >>>regards
> >>>
> >>>
> >>>Daniel
> >>>
> >>>
> >>>-------- Original-Nachricht --------
> >>>Datum: Fri, 28 Jul 2006 10:26:38 +0200
> >>>Von: "Bart van den Eijnden (OSGIS)" <bartvde at xs4all.nl>
> >>>An: Daniel Goetz <madprof at GMX.CH>
> >>>Betreff: Re: [UMN_MAPSERVER-USERS] WMS and SRS
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>>Hi Daniel,
> >>>>
> >>>>please remember that if the ratio of your bbox and the ratio of your
> >>>>width versus height in pixels, differs, the map will be stretched.
> That
> >>>>could explain some of the behaviour. You need to make sure that the
> >>>>values in your WMS request have the same ratio. I don't know if this
> is
> >>>>the problem, but it could be a cause.
> >>>>
> >>>>Proj.4 has a utility to reproject. The proj utilities also come with
> >>>>MS4W. See also:
> >>>>
> >>>>http://proj.maptools.org/man_cs2cs.html
> >>>>
> >>>>Best regards,
> >>>>Bart
> >>>>
> >>>>Daniel Goetz wrote:
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>>Hi,
> >>>>>
> >>>>>thank you Frank, Trond and Ed for your help. I tried to use
> reporjected
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>coordinates as BBOX-values in my "new" WMS-GetMap-request
> >>>>
> >>>>
> >>(SRS=WPSG:4326)
> >>
> >>
> >>>>and it works now. I got the new reprojected coordinates out of the
> >>>>GetCapabilities document (I took them out of the LatLonBoundingBox
> >>>>
> >>>>
> >>paragraph in the
> >>
> >>
> >>>>GetCapabilities document):
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>><Layer queryable="1" opaque="0" cascaded="0">
> >>>>> <Name>VIEW_RWG_TBS</Name>
> >>>>> <Title>RWG_TM_NR</Title>
> >>>>> <SRS>EPSG:31468</SRS>
> >>>>> <SRS>EPSG:4326</SRS>
> >>>>> <LatLonBoundingBox minx="10.9905" miny="49.3319" maxx="11.2852"
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>maxy="49.5441" />
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>> <BoundingBox SRS="EPSG:31468"
> >>>>> minx="4.42695e+006" miny="5.46647e+006"
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>maxx="4.44806e+006" maxy="5.48982e+006" />
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>> <Style>
> >>>>> <Name>default</Name>
> >>>>> <Title>default</Title>
> >>>>> <LegendURL width="20" height="10">
> >>>>> <Format>image/png</Format>
> >>>>> <OnlineResource xmlns:xlink="http://www.w3.org/1999/xlink"
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>xlink:type="simple"
> >>>>xlink:href="http://10.65.112.50/cgi-bin/mapserv.exe?map=/ms4w/apache/htdocs/WMS/WMS_BRWK.map&version=1.1.1&service=WMS&request=GetLegendGraphic&layer=VIEW_RWG_TBS&format=image/png"/>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>> </LegendURL>
> >>>>> </Style>
> >>>>> </Layer>
> >>>>>
> >>>>>
> >>>>>But I have two further questions:
> >>>>>
> >>>>>When I do a WMS-GetMap-request in the "new" SRS (EPSG:4326) the map
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>maserver sends back does not vary form the map mapserver generates
> when
> >>>>
> >>>>
> >>sending
> >>
> >>
> >>>>a GetMap-request in the "original" SRS (EPSG:31468). I mean there is
> no
> >>>>deformation/distortion noticeable. But when I do a "normal" mapserver
> >>>>mode=browse-request in my simple pan and zoom template and tell
> >>>>
> >>>>
> >>mapserver to
> >>
> >>
> >>>>reproject the data in EPSG:4326 (I do that by putting the
> >>>>
> >>>>
> >>PROJECTION-object in
> >>
> >>
> >>>>the MAP-object of the .map-file to "init=epsg:4326" while the
> >>>>PROJECTION-objects in the LAYER-objects are still in the "origninal"
> >>>>
> >>>>
> >>"init=epsg:31468"
> >>
> >>
> >>>>projection. Of course I change the EXTENT-parameters in the .map-file
> >>>>
> >>>>
> >>too. Am
> >>
> >>
> >>>>I doing right?) the returned map looks different >from the map
> >>>>
> >>>>
> >>genereated
> >>
> >>
> >>>>using the "original" projection. I mean that the reprojected map using
> >>>>mode=browse looks deformed/distorted compared to the "original" not
> >>>>
> >>>>
> >>reprojected
> >>
> >>
> >>>>map.
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>>The question is now: Why do the two maps (the reprojected one I get
> >>>>>
> >>>>>
> >>from
> >>
> >>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>the WMS-GetMap-request and the reprojected map I get by a mode=browse
> >>>>request) differ in their appearence (distortion) although I tell
> >>>>
> >>>>
> >>mapserver in
> >>
> >>
> >>>>both cases to reproject the map to "epsg:4326"?
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>>The secoond question is: As mentioned I got the "new" reprojeted
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>coordinates for BBOX-values out of the GetCapabilities document. But
> is
> >>>>
> >>>>
> >>there a
> >>
> >>
> >>>>program that could do coordinate transformation for me, so that I am
> >>>>
> >>>>
> >>able to
> >>
> >>
> >>>>transform "epsg:31468" coordinates to "epsg:4326" coordinates?
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>>OK, that's it. Thak you again for your helpful hints. And would be
> very
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>nice of you if you could help me further on with my problems/questions
> >>>>elucidated in this email. Thank you so much.
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>>regards
> >>>>>
> >>>>>Daniel
> >>>>>
> >>>>>
> >>>>>-------- Original-Nachricht --------
> >>>>>Datum: Thu, 27 Jul 2006 09:22:21 -0400
> >>>>>Von: Ed McNierney <ed at TOPOZONE.COM>
> >>>>>An: MAPSERVER-USERS at LISTS.UMN.EDU
> >>>>>Betreff: Re: [UMN_MAPSERVER-USERS] WMS and SRS
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>>Daniel -
> >>>>>>
> >>>>>>I think Frank's theory is likely to be correct, and that there is a
> >>>>>>problem with the BBOX coordinates used in your new request. It
> sounds
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>like the
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>>>changes you made are fine, although I think it is not necessary to
> add
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>all
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>>>supported SRS systems to the metadata for each layer - just the
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>MAP-level
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>>>metadata should be all you need to do.
> >>>>>>
> >>>>>>Can you post the SRS= and BBOX= parameters you are using in your
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>original
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>>>epsg:31468 request and in the new epsg:4326 requests?
> >>>>>>
> >>>>>> - Ed
> >>>>>>
> >>>>>>Ed McNierney
> >>>>>>President and Chief Mapmaker
> >>>>>>TopoZone.com / Maps a la carte, Inc.
> >>>>>>73 Princeton Street, Suite 305
> >>>>>>North Chelmsford, MA 01863
> >>>>>>ed at topozone.com
> >>>>>>(978) 251-4242
> >>>>>>
> >>>>>>-----Original Message-----
> >>>>>>From: UMN MapServer Users List
> [mailto:MAPSERVER-USERS at LISTS.UMN.EDU]
> >>>>>>
> >>>>>>
> >>On
> >>
> >>
> >>>>>>Behalf Of Daniel Goetz
> >>>>>>Sent: Thursday, July 27, 2006 3:05 AM
> >>>>>>To: MAPSERVER-USERS at LISTS.UMN.EDU
> >>>>>>Subject: [UMN_MAPSERVER-USERS] WMS and SRS
> >>>>>>
> >>>>>>Hi coummunity,
> >>>>>>
> >>>>>>I built up a littel WMS-server with umn-mapserver (local
> installation;
> >>>>>>ms4w 2.1). The "original" projection of the single Layers is alway
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>epsg:31468
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>>>(these are cartesian Gauß-Krüger-coordiantes). So I set the
> >>>>>>PORJECTION-object of each LAYER and in the MAP-object to
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>"init=epsg:31468". In the
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>>>METADATA of the MAP-object as well as in the single LAYER-objects I
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>defined
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>>>"wms_srs" as "EPSG:31468" as well. For testing purpose I did some
> >>>>>>WMS-GetMap-Requests with "SRS=EPSG:31468" and everything went fine.
> >>>>>>
> >>>>>>But now I want to make my WMS-service more interchangeable, so I
> want
> >>>>>>
> >>>>>>
> >>to
> >>
> >>
> >>>>>>define some more SRSs in that the WMS should be able to be
> displayed.
> >>>>>>
> >>>>>>
> >>I
> >>
> >>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>want
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>>>to make it possible to "transform" (don't know the exact word in
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>english)
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>>>the WMS from its original Projection to another SRS (e.g. WGS 84;
> >>>>>>EPSG:4326). In my opinion this should be possible by adding another
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>epsg-code to the
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>>>METADATA. So my METADATA (both in the MAP and in the LAYERs-objects)
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>look
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>>>like this: "wms_srs" "EPSG:31468 EPSG:4326".
> >>>>>>
> >>>>>>But now every time I change the SRS block in my WMS-GetMap-request
> >>>>>>
> >>>>>>
> >>from
> >>
> >>
> >>>>>>"SRS=EPSG:31468" to "SRS=EPSG:4326" mapserver returns a blank image.
> I
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>even
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>>>tried to set the BBOX to latlon-coordinates when using
> "SRS=EPSG:4326"
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>but
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>>>even this failed. I also testes other SRSs (both geographic ones and
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>real
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>>>projections) but with no success.
> >>>>>>
> >>>>>>Could anybody please give me some help or hints what to do and what
> >>>>>>
> >>>>>>
> >>went
> >>
> >>
> >>>>>>wrong and why did this happen? I would be very glad and thankful.
> >>>>>>
> >>>>>>
> >>Thank
> >>
> >>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>you
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>>>so much.
> >>>>>>
> >>>>>>
> >>>>>>regards
> >>>>>>
> >>>>>>
> >>>>>>Daniel
> >>>>>>
> >>>>>>
> >>>>>>--
> >>>>>>
> >>>>>>
> >>>>>>Der GMX SmartSurfer hilft bis zu 70% Ihrer Onlinekosten zu sparen!
> >>>>>>Ideal für Modem und ISDN: http://www.gmx.net/de/go/smartsurfer
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>--
> >>>>Bart van den Eijnden
> >>>>OSGIS, Open Source GIS
> >>>>http://www.osgis.nl
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>
> >>>
> >>>
> >>>
> >>--
> >>Bart van den Eijnden
> >>OSGIS, Open Source GIS
> >>http://www.osgis.nl
> >>
> >>
> >
> >
> >
>
>
> --
> Bart van den Eijnden
> OSGIS, Open Source GIS
> http://www.osgis.nl
--
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