WMS and SRS
Bart van den Eijnden (OSGIS)
bartvde at XS4ALL.NL
Fri Jul 28 02:21:43 PDT 2006
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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