[PROJ] EPSG:4326 --> EPSG:5677

[Roger Oberholtzer]

On Wed, Sep 24, 2025 at 10:57 AM Even Rouault <even.rouault at spatialys.com>
wrote:

> Robert,
>
> the more precise transformation between both datums involves the use of
> this grid file : https://cdn.proj.org/de_adv_BETA2007.tif  . Make sure it
> is installed in the same directory where proj.db is located
>
> cf:
>
> $ projinfo EPSG:4326 EPSG:5677 --spatial-test intersects --grid-check none
> -o PROJ
> Candidate operations found: 3
> -------------------------------------
> Operation No. 1:
>
> unknown id, Inverse of DHDN to WGS 84 (4) + 3-degree Gauss-Kruger zone 3,
> 1 m, Germany - onshore - states of Baden-Wurtemberg, Bayern, Berlin,
> Brandenburg, Bremen, Hamburg, Hessen, Mecklenburg-Vorpommern,
> Niedersachsen, Nordrhein-Westfalen, Rheinland-Pfalz, Saarland, Sachsen,
> Sachsen-Anhalt, Schleswig-Holstein, Thuringen., at least one grid missing
>
> PROJ string:
> +proj=pipeline
>   +step +proj=axisswap +order=2,1
>   +step +proj=unitconvert +xy_in=deg +xy_out=rad
>   +step +inv +proj=hgridshift +grids=de_adv_BETA2007.tif
>   +step +proj=tmerc +lat_0=0 +lon_0=9 +k=1 +x_0=3500000 +y_0=0
> +ellps=bessel
>
> Grid de_adv_BETA2007.tif needed but not found on the system. Can be
> obtained at https://cdn.proj.org/de_adv_BETA2007.tif
>

I have the DE grid shift files on my Linux system in:

/usr/share/proj/de_adv_BETA2007.tif
/usr/share/proj/de_adv_README.txt
/usr/share/proj/de_bkg_README.txt
/usr/share/proj/de_bkg_gcg2016.tif
/usr/share/proj/de_geosn_NTv2_SN.tif
/usr/share/proj/de_geosn_README.txt
/usr/share/proj/de_hvbg_README.txt
/usr/share/proj/de_hvbg_hessen_HeTA2010.tif
/usr/share/proj/de_lgl_bw_BWTA2017.tif
/usr/share/proj/de_lgl_bw_README.txt
/usr/share/proj/de_lgvl_saarland_README.txt
/usr/share/proj/de_lgvl_saarland_SeTa2016.tif
/usr/share/proj/de_tlbg_thueringen_NTv2gridTH.tif
/usr/share/proj/de_tlbg_thueringen_README.txt

/usr/share/proj is also where proj.db and proj.ini are located.


I see that three possible operations are listed. To be honest, I do not
know which one is most appropriate. I am guessing that #1 is the default.
How would I choose one of the other sets of operations? Use the listed
strings as the destination CRS? Or is there some other way to select it?
Should the reported altitude always be over the new ellipsoid?


>
>
>
> Even
> Le 24/09/2025 à 08:57, Roger Oberholtzer via PROJ a écrit :
>
>
>
> I am trying to project some EPSG:4326 locations (from a GPS) to
> EPSG:5677 (DHDN Germany Zone 3). I have sample data from the German road
> authorities (BASt). They feel that the locations provided by proj (9.6.0)
> are consistently 1.5 meters or so away from that they expect. They were
> also expecting a change in altitude as the ellipsoid was different. I have
> implemented this with something like this:
>
> myCRS = proj_create_crs_to_crs( 0,  "EPSG:4326",  "EPSG:5677",  0);
>
> And then calling proj_trans(myCRS, PJ_FWD, PJ_COORD);
>
> My question is if I need to do more than this as EPSG:5677 is ellipsoid
> Bessel 1841.
>
> --
> Roger Oberholtzer
>
> _______________________________________________
> PROJ mailing listPROJ at lists.osgeo.orghttps://lists.osgeo.org/mailman/listinfo/proj
>
> -- http://www.spatialys.com
> My software is free, but my time generally not.
>
>

-- 
Roger Oberholtzer
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