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How to fix a CRS definition?

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How to fix a CRS definition?

Anita Graser
Hi,

In my QGIS 1.8 install on Ubuntu EPSG:31287 is defined as

+proj=lcc +lat_1=49 +lat_2=46 +lat_0=47.5 +lon_0=13.33333333333333
+x_0=400000 +y_0=400000 +ellps=bessel +datum=hermannskogel +units=m
+no_defs

while according to http://spatialreference.org/ref/epsg/31287/proj4/
(and the definition used in PostGIS) it should be

+proj=lcc +lat_1=49 +lat_2=46 +lat_0=47.5 +lon_0=13.33333333333333
+x_0=400000 +y_0=400000 +ellps=bessel
+towgs84=577.326,90.129,463.919,5.137,1.474,5.297,2.4232 +units=m
+no_defs

Has this been fixed in Master? Is it possible to change this for 1.8
on my machine? It seems to cause an east-west offset.

Best wishes,
Anita
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Re: How to fix a CRS definition?

Anita Graser
Just wanted to add that the definition is correct in both QGIS 1.8 and
Master on my OSGeo4W system.

Best wishes,
Anita
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Re: How to fix a CRS definition?

Andre Joost
In reply to this post by Anita Graser
Am 23.12.2012 12:32, schrieb Anita Graser:

> Hi,
>
> In my QGIS 1.8 install on Ubuntu EPSG:31287 is defined as
>
> +proj=lcc +lat_1=49 +lat_2=46 +lat_0=47.5 +lon_0=13.33333333333333
> +x_0=400000 +y_0=400000 +ellps=bessel +datum=hermannskogel +units=m
> +no_defs
>
> while according to http://spatialreference.org/ref/epsg/31287/proj4/
> (and the definition used in PostGIS) it should be
>
> +proj=lcc +lat_1=49 +lat_2=46 +lat_0=47.5 +lon_0=13.33333333333333
> +x_0=400000 +y_0=400000 +ellps=bessel
> +towgs84=577.326,90.129,463.919,5.137,1.474,5.297,2.4232 +units=m
> +no_defs
>
> Has this been fixed in Master? Is it possible to change this for 1.8
> on my machine? It seems to cause an east-west offset.

The '+datum=hermannskogel' is hardcoded in proj:
<https://svn.osgeo.org/metacrs/proj/branches/4.8/proj/src/pj_datums.c>
with a three-parameter transformation:
"hermannskogel", "towgs84=653.0,-212.0,449.0"

Seven-parameter transformations are more precise, the official
parameters can be found here:
<http://mapref.org/GeodeticReferenceSystemsAT.html>

The latest build of gdal uses the 7 parameters you listed above.

If you want to change the values, look for srs.db. You can edit it with
spatialite, or just copy it from the windows installations.

Greetings
André Joost





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Re: How to fix a CRS definition?

Jürgen E. Fischer
In reply to this post by Anita Graser
Hi Anita,

On Sun, 23. Dec 2012 at 12:32:21 +0100, Anita Graser wrote:
> Has this been fixed in Master? Is it possible to change this for 1.8 on my
> machine? It seems to cause an east-west offset.

The definitions are taken from your local GDAL version on install.  So you'll
probably see the same results in gdalsrsinfo -o proj4 EPSG:31287.


Jürgen

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