[Qgis-user] georeferencing

Andreas Neumann a.neumann at carto.net
Thu Mar 1 02:06:18 PST 2012


 Hi,

 QGIS can reproject rasters on the fly. I believe from Version 1.7x on - 
 definitely with the trunk version.

 However, if you use Google maps or Openstreetmap through the OpenLayers 
 plugin you fixed to their projection.

 Reprojecting your own data to their projection should still work 
 though.

 If it doesn't, please provide more details - it may be a bug then.

 Andreas

 On Thu, 1 Mar 2012 09:53:50 +0000, M.E.Dodd wrote:
> I want to show a detailed map of buildings and vegetation over a
> background image e.g. openstreetmap or google etc. Don't think qgis
> can do on the fly transformation of rasters at moment so assume I 
> have
> to geocode the detailed map using epsg:900913 so it can be shown with
> openstreetmap. Converted a set of fixed point locations from original
> map into google's x and y then did the geocoding in qgis and plotted
> over openstreetmap. The individual points then came out in the 
> correct
> place but the map itself was shown about 19km too far north. If I'd
> had made a mistake in the x,y coordinates or the coordinate system
> then the points should not be in the correct place so I am a bit
> mystified as to what has happened and how to go about fixing it.
> The map I am trying to georeference is a .tiff with transparency
> hoping that this would allow the details to show over the background,
> however the 'transparent' part is showing up black at the moment so
> some adjustment here needed too.
>
>  --
>  The Open University is incorporated by Royal Charter (RC 000391), an
> exempt charity in England & Wales and a charity registered in 
> Scotland
> (SC 038302).

-- 
 --
 Andreas Neumann
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 8624 Grüt (Gossau ZH)
 Switzerland



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