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

[Victoria Agazzi]

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
>   
>
> ------------------------------------------------------------------------
>
> ------------------------------------------------------------------------
>
> _______________________________________________
> Gvsig_internacional mailing list
> Gvsig_internacional at runas.cap.gva.es
> http://runas.cap.gva.es/mailman/listinfo/gvsig_internacional
>