[Qgis-user] wg84 projection problem

[Otto Dassau]

On Thu, 29 Oct 2009 15:54:44 +0700
Markus Nater <mark.nater at gmail.com> wrote:

> thank you Alex
> and thank you Otto
> 
> when I do take a projected coord system (set to wgs84 zone 47N), the 
> measurements are correct.
> but then arises a new problem, as I have a raster shaded relief as 
> geotiff overlayed, that is referenced in wgs84. projection on the fly 
> makes this raster invisible... strangely! and I havent found out how to 
> work around this yet. i cant work out to reproject this raster either, 
> somehow nothing ever happens using the gdal raster translation.
> any ideas how to solve this little problem? :-)

your data in "wgs84 zone 47N" is probably something like: 

CRS: Projected Coordinate System "UTM zone 47N"
Ellipsoid: WGS84

=> EPSG: 32647 ?

and the WGS 84 raster might be: 

CRS: Geographic Coordinate System "WGS84" 
Ellipsoid: WGS 84

=> EPSG: 4326 ?

that would mean your 2 layers are projected in 2 different CRS. 

QGIS supports OTF for vector layers. So you can load a raster, define its
CRS, activate OTF and then load a vector layer projected in another CRS. 

Regards,
 Otto

> cheers
> markus
> 
> 
> Alex Mandel schrieb:
> > Markus Nater wrote:
> >   
> >> Hi List
> >>
> >> I have some polygons in qgis with wgs84 projection. But when I try to
> >> measure distance in meters, it gives me back 1cm for 0.1 degrees, which
> >> is of course totally wrong.
> >> how can I fix this, so I will have the correct measurements in meters?
> >>
> >> cheers
> >> markus
> >>
> >>     
> >
> > Enable projection on the fly, and pick a projected coordinate system.
> > Technically in WGS84 the best you could get is great circle distances,
> > and I'm not sure the measure tool does this yet. So you need to be in a
> > projection that flattens the map evenly for distance measurement.
> >
> > Alex
> >
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