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<p>Robert,</p>
<p>the more precise transformation between both datums involves the
use of this grid file : <a class="moz-txt-link-freetext" href="https://cdn.proj.org/de_adv_BETA2007.tif">https://cdn.proj.org/de_adv_BETA2007.tif</a>
. Make sure it is installed in the same directory where proj.db is
located</p>
<p>cf:<br>
<br>
$ projinfo EPSG:4326 EPSG:5677 --spatial-test intersects
--grid-check none -o PROJ<br>
Candidate operations found: 3<br>
-------------------------------------<br>
Operation No. 1:<br>
<br>
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<br>
<br>
PROJ string:<br>
+proj=pipeline<br>
+step +proj=axisswap +order=2,1<br>
+step +proj=unitconvert +xy_in=deg +xy_out=rad<br>
+step +inv +proj=hgridshift +grids=de_adv_BETA2007.tif<br>
+step +proj=tmerc +lat_0=0 +lon_0=9 +k=1 +x_0=3500000 +y_0=0
+ellps=bessel<br>
<br>
Grid de_adv_BETA2007.tif needed but not found on the system. Can
be obtained at <a class="moz-txt-link-freetext" href="https://cdn.proj.org/de_adv_BETA2007.tif">https://cdn.proj.org/de_adv_BETA2007.tif</a><br>
<br>
<br>
</p>
<p>Even<br>
</p>
<div class="moz-cite-prefix">Le 24/09/2025 à 08:57, Roger
Oberholtzer via PROJ a écrit :<br>
</div>
<blockquote type="cite"
cite="mid:CANkOqwOU+L+2CynqVLWobx3rLN8W=Q+3driN5xzWuiNRVLKwgQ@mail.gmail.com">
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<div><br clear="all">
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<br>
<div
style="font-family:Aptos,"Aptos_EmbeddedFont","Aptos_MSFontService",Calibri,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">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:</div>
<div
style="font-family:Aptos,"Aptos_EmbeddedFont","Aptos_MSFontService",Calibri,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><br>
</div>
<div
style="font-family:Aptos,"Aptos_EmbeddedFont","Aptos_MSFontService",Calibri,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">myCRS
= proj_create_crs_to_crs( 0, "EPSG:4326", "EPSG:5677", 0);</div>
<div
style="font-family:Aptos,"Aptos_EmbeddedFont","Aptos_MSFontService",Calibri,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><br>
</div>
<div
style="font-family:Aptos,"Aptos_EmbeddedFont","Aptos_MSFontService",Calibri,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">And
then calling proj_trans(myCRS, PJ_FWD, PJ_COORD);</div>
<div
style="font-family:Aptos,"Aptos_EmbeddedFont","Aptos_MSFontService",Calibri,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><br>
</div>
<div
style="font-family:Aptos,"Aptos_EmbeddedFont","Aptos_MSFontService",Calibri,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">My
question is if I need to do more than this as EPSG:5677 is
ellipsoid Bessel 1841. </div>
<div
style="font-family:Aptos,"Aptos_EmbeddedFont","Aptos_MSFontService",Calibri,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"> </div>
<span class="gmail_signature_prefix">-- </span><br>
<div dir="ltr" class="gmail_signature"
data-smartmail="gmail_signature">Roger Oberholtzer</div>
</div>
<br>
<fieldset class="moz-mime-attachment-header"></fieldset>
<pre class="moz-quote-pre" wrap="">_______________________________________________
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</blockquote>
<pre class="moz-signature" cols="72">--
<a class="moz-txt-link-freetext" href="http://www.spatialys.com">http://www.spatialys.com</a>
My software is free, but my time generally not.</pre>
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