[Gvsig_english] transform projection problem: epsg 4326 (wgs84) --> epsg 31468 (GK Zone 4)

[Wolfgang Qual]

Hi Victoria,
thanks for your answer. 
Well, I tried out both options and the second (transformation code 1777) fits quite good. Nevertheless, the dialogue is a little bit confusing (it is working, but the number of the source and target CRS is 
different to what I expected). It was only try and error... Regarding manual transformation: I do not know the paramters needed.

Best,
Wolfgang
-------- Original-Nachricht --------
> Datum: Wed, 18 Jun 2008 09:14:28 +0200
> Von: Victoria Agazzi <agazzi_vic at gva.es>
> An: Users and Developers mailing list <gvsig_internacional at runas.cap.gva.es>
> Betreff: Re: [Gvsig_english] transform projection problem: epsg 4326 (wgs84)	--> epsg 31468 (GK Zone 4)

> Hi Wolfgang,
> here are some questions and comments about your problem:
> Step 5: Do you select any reprojection in the dialog box even if none of 
> them fits you?
> You have to bear in mind that the transformation is made between the two 
> geodetic reference systems, not between the geodetic (wgs84) and the 
> projected one (31468). In your case, if you select the 
> epsg_transformation, you can choose between the parameter's sets coded 
> 1673 or 1777. Which one is the best for you? well, both seem to have the 
> same area description but obviously must use different sets of parameter 
> transformation. In order to try, I 'd do the reprojection with both and 
> compare as you did first. If none fits you and you know the parameters 
> of the ESRI transformation you've applied, you can also try to use the 
> manual transformation instead.
> 
> Regards,
> Viqui-.
> 
> 
> Wolfgang Qual escribió:
> > Dear list,
> > I have a problem when trying to add a shapefile which was derived from a
> gps-receiver (gpx-file was transformed to shapefile using gpx2shp). For
> me, it is not possible to transform the projection 4326 (wgs84) into
> Gauss-Krüger epgs 31468 (which is, zone 4, Germany). What I did so far:
> >
> > 1) add a new view in gvSIG, set projection to wgs84. Open this view
> > 2) add the shapefile
> > 3) open the geoprocessing wizard, select tool "Reproject"
> > 4) within this dialogue: Set source projection to 4326 and target
> projection to 31468
> > 5) select there: type epsg_transformation.
> > However, within this dialogue, it is not possible to select a
> reprojection that really fits to my needs. Well, I did not worry much about it and
> created the projected shapefile. 
> > 6) for comparision, I made a reprojection using ogr2ogr-command line
> tool:
> > ogr2ogr -f "ESRI Shapefile" /tmp/ogr2ogr_test.shp -t_srs EPSG:31468
> -s_srs EPSG:4326 /Netzlaufwerke/uis/tmp/data_trk_trk.shp
> >
> > You can see both results in the attached image (blue: gvSIG projected
> dataset, red: ogr2ogr generated dataset; background is a 31468-background of
> the survey department). Whereas the ogr2ogr-dataset fits quite good to the
> background, there is a clear offset within the gvSIG-generated dataset.
> >
> > The question for me is now: is there no transformation defined that fits
> for my needs in gvSIG? Will it be included soon? Is it a bug or is there a
> workaround?
> >
> > Your comments are appreciated as always.
> > Best regards,
> > Wolfgang
> >   
> >
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