[Qgis-user] Projection

Wed Jan 7 07:50:41 PST 2009

hi,

be carefull about on-the-fly-projection with wgs84-data and austrian data (MGI) because there are a few different towgs-informations in the epsg-database. 

so if the towgs-information is not considered, there can be a north-east shift of about 75m during the on-the-fly-projection.

i prepared some information about this issue under

http://www.alectoria.at/content/view/17/1/

also i prepared there some prj-files including the towgs-information for Austria.

best regards
helli

-------------------------------------
  helmut kudrnovsky
  www.alectoria.at

------------------------------

Message: 3
Date: Wed, 7 Jan 2009 09:05:46 +0100
From: Otto Dassau <otto.dassau at gmx.de>
Subject: Re: [Qgis-user] Projection
To: qgis-user at lists.osgeo.org
Message-ID: <20090107090546.12b1c76a at nature>
Content-Type: text/plain; charset=US-ASCII

Hi Werner, 

I tried to find your raster file projection "UTM_WGS84_M15", but it doesn't seem
to be available. What happens if you create your own CRS in QGIS. From your .prj
file this should work:

Setings -> Custom CRS

Name: UTM_WGS84_M15
Parameters: +proj=tmerc +lat_0=0 +lon_0=15 +k=0.9996 +x_0=500000 +y_0=-5000000
+ellps=WGS84 +units=m +datum=WGS84 +no_defs

Then you load the raster, which is projected in "UTM_WGS84_M15", choose your
custom projection in the Project Properties dialog, select "Enable OTF" and
load the shape. The vector should now fit with the raster.

 regards,
  Otto

On Mon, 05 Jan 2009 09:30:20 +0100
Werner Macho <werner.macho at gmail.com> wrote:

> Hi List!
> 
> I gotta small problem here to proof that qgis is prime-time ready but ..
> i have a raster and 3 vektor layers that i want to overlay
> Rasterlayer is a geoTIF and as of .prj file:
>
PROJCS["UTM_WGS84_M15",GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1
984",6378137,298.257223563]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519
943295]],PROJECTION["Transverse_Mercator"],PARAMETER["False_Easting",500000],PA
RAMETER["False_Northing",-5000000],PARAMETER["Central_Meridian",15],PARAMETER["
Scale_Factor",0.9996],PARAMETER["Latitude_Of_Origin",0],UNIT["Meter",1]]
> 
> therefore a UTM_WGS84_M15 which seems to be not in the list of 
> projections (or am i wrong?)
> 
> the Vektorlayers are normal shape files and as of .prj file:
>
PROJCS["MGI_Austria_GK_M34",GEOGCS["GCS_MGI",DATUM["D_MGI",SPHEROID["Bessel_184
1",6377397.155,299.1528128]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925
199433]],PROJECTION["Transverse_Mercator"],PARAMETER["False_Easting",750000.0],
PARAMETER["False_Northing",-5000000.0],PARAMETER["Central_Meridian",16.33333333
333334],PARAMETER["Scale_Factor",1.0],PARAMETER["Latitude_Of_Origin",0.0],UNIT[
"Meter",1.0]]
> 
> which i expect to be the MGI / Austria M34 projection and i can find it 
> in the KBS List
> 
> 
> So can anybody give me a hint howto solve the rasterlayer projection 
> because otherwise i cant overlay vector OTF on the Raster (My 
> Information is that it can only work in that direction.
> 
> Thanks a lot
> regards
> Werner
> _______________________________________________
> Qgis-user mailing list
> Qgis-user at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/qgis-user

------------------------------

Message: 4
Date: Wed, 07 Jan 2009 11:34:35 +0100
From: Werner Macho <werner.macho at gmail.com>
Subject: Re: [Qgis-user] Projection
To: Otto Dassau <otto.dassau at gmx.de>
Cc: qgis-user at lists.osgeo.org
Message-ID: <4964853B.8030003 at gmail.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Hi Otto! (and list)

Thanks for your help. It worked.
At least in Windows - because i can remember that i tried nearly the 
same with Linux and it did not.
But I have to check that anyway when I'm back home and on my Linux-PC.
Expect a mail with a report on linux too ;)

So it seems that there is really no existing projection for the (in 
austria) common UTM WGS84 M15.
And nevertheless - all files i loaded into QGIS where fully equipped 
with a .prj file.
So were there any discussion about reading .prj files i missed or can 
someone (hopefully a developer) provide me some information why QGIS is 
not reading .prj infos?
At least a small button with "read prj file" to give the right .prj file 
for reading raster or vector files would even be more helpfull (and at 
least easier) than defining the projection by myself.
I know it's the same as SPSS vs. R where it can lead to wrong 
interpreted results using a click-click interface compared to a 
"console-driven" text interface where you really have to know what you 
are doing but .. see the .prj files are provided so why looking for the 
projection if it is already there?

Is there any ongoing discussion about trying to read the .prj files 
automatically or at least integrate them in the loading process somehow?

thanks to all for your help and information

regards
werner
> Hi Werner, 
>
> I tried to find your raster file projection "UTM_WGS84_M15", but it doesn't seem
> to be available. What happens if you create your own CRS in QGIS. From your .prj
> file this should work:
>
> Setings -> Custom CRS
>
> Name: UTM_WGS84_M15
> Parameters: +proj=tmerc +lat_0=0 +lon_0=15 +k=0.9996 +x_0=500000 +y_0=-5000000
> +ellps=WGS84 +units=m +datum=WGS84 +no_defs
>
> Then you load the raster, which is projected in "UTM_WGS84_M15", choose your
> custom projection in the Project Properties dialog, select "Enable OTF" and
> load the shape. The vector should now fit with the raster.
>   
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