[Proj] proj: NTv2 for Baden-Württemberg

[Tobias Wendorff]

Hi there,

in Germany, two further states are currently switching to UTM32 (Bavaria
and Baden-Württemberg). Both have published the NTv2 files as OpenData.

Since I had a set of GK3 coordinates (EPSG:31467) from Baden-Würtemberg,
I checked if the new version 5.0.1 of "proj" can process the data free
of error. Short answer: yes, it can. And it does it accurately.

For those who may be looking for the working parameters or want to
do some test, here is a short guide:

1. goto website to read license
https://www.lgl-bw.de/lgl-internet/opencms/de/05_Geoinformation/Liegenschaftskataster/ETRS89-UTM/

2. download and unzip the binary
https://www.lgl-bw.de/lgl-internet/web/sites/default/de/05_Geoinformation/Galerien/Dokumente/BWTA2017.zip

3. run it
./cs2cs -vvvv -f "%.3f" +proj=tmerc +lat_0=0 +lon_0=9 +k=1.000000
+x_0=3500000 +y_0=0 +ellps=bessel +units=m +nadgrids=./BWTA2017.gsb +to
+proj=utm +ellps=GRS80 +zone=32 +nadgrids=@null

4. reference data (with comparism to BETA2017):
BWTA2017: 3413441.910 5374863.910 => 413400.952 5373153.284
BETA2017: 3413441.910 5374863.910 => 413401.020 5373153.319
BETA2017: 2552401.862 5616707.524 => 340408.064 5617072.481

All fine, good work.

Oh, by the way: it does *not* work with the ascii file (BWTA2017.gsa).

Best regards,
Tobias