[Qgis-user] WMS Image Projection

[kirk]

Hi Springer.  My mistake, you will require a local grid shift file, BC_93_05.gsb. The NTv2 is a national NAD27to NAD83 grid shift file. The BC_93_95 provides localized conversion from Nad83 (original) to Nad83 (csrs). Sent from my Galaxy
-------- Original message --------From: Springfield Harrison <stellargps at gmail.com> Date: 2021-04-08  5:24 a.m.  (GMT-04:00) To: Andreas Neumann <a.neumann at carto.net> Cc: qgis-user <qgis-user at lists.osgeo.org> Subject: Re: [Qgis-user] WMS Image Projection 
    Hi Andreas,
    Thanks for the reply, I'll try to clarify:
    
      Version is 3.16.4
      The two municipal sources are being viewed in their own web
        windows and are displaying the same data
      
      
        They are the source of the property lines for my GIS
          (downloaded shapefile) and the orthophoto (WMS link, not
          resident TIFF or other)
        
      
      The property lines are EPSG:3157
          - NAD83(CSRS) / UTM zone 10N - Projected, and from the
          municipal source.  I've attached the shapefile if you have the
          time.
        
      In QGIS, the ortho is loaded from the WMS source
      
      
        https://mapservices.crd.bc.ca/arcgis/services/OrthoImagery2019/MapServer/WMSserver
        EPSG:26910
            - NAD83 / UTM zone 10N - Projected
      
      The project CRS is EPSG: 26910 but it doesn't seem to change
        anything by changing that or the source projections (at least
        within versions of NAD83 UTM Zone 10N)
        
      Thus, the same information displays differently online versus
        in QGIS.
      
        The shift seems to be 1.5 m +/-, quite a lot for what I'm
          trying to do (building permit with tight setbacks).
          
        These
            are commonly used projections for our neck of the woods
        The two
            images I sent earlier depict the differences; in QGIS,
            earlier orthophotos show a similar or worse displacement. 
            Not so on the municipal web viewer.
      
      I've read up on projections in the tutorial and Help file, no
        revelations there, at least that I could see.
    
    Thanks very much for any thoughts you may have.
    -----
Cheers, Spring
    
    
    
    
    On 08/Apr/2021 00:47, Andreas Neumann
      wrote:
    
    
      
      Hi,
      Are there two different CRS involved here? Are the vectors
        (parcel boundaries) in a different CRS than the orthoimages?
        This might be a problem of a missing grid-shift file in QGIS.
      It is also unclear for me if you load your Orthoimages locally
        (from tiff-files as well) or from WMS (or both) and only one of
        them is shifted?
      Can you also add information what QGIS version with what proj
        version you use? You can find this information in the about
        dialogue in the help menu.
      Greetings,
      Andreas
      On 2021-04-08 02:37, Springfield Harrison
        wrote:
      
        Hello All,
          
          Re obtaining orthophotos from a WMS server.
          
          Locally we have orthophotos that can be brought into QGIS
          using the WMS service.  They are also viewable on the local
          government web map service.  In both cases I can compare them
          to the property lines which are from the same source.
          
          On the government web pages (2), the orthophotos and the lot
          lines appear to coincide very well.  In QGIS, the same two
          layers are quite misaligned.
          
          One would suspect a CRS problem but changing the CRS of the
          Project and the WMS image in QGIS has no effect.  Even
          followed the tutorial to no effect.
          
          I'm attaching screen shots of the two results.  Ant thoughts
          would be appreciated, thank you . . . .
          
          -----
          Cheers, Springfield Harrison
          
          
        
        
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