BWTA2017 transformation

BWTA2017 is the new NTv2 grid for transformation between Gauß-Krüger and UTM in Baden-Württemberg.

The transformation is published as open data (License: https://www.govdata.de/dl-de/by-2-0) by the LGL (Landesamt für Geoinformation und Landentwicklung).
To download and for further information (mostly in German), see:

• LGL: ETRS89-UTM - Baden-Württembergischer Transformationsansatz für ALKIS 2017
• Download BWTA2017.zip

Computations are based on data of LGL, www.lgl-bw.de (Datengrundlage: LGL, www.lgl-bw.de)

If you wan to include it in QGIS, see this detailed explanation (in german) and replace BETA2007 accordingly: Praezise_Transformation_im_QGIS_mit_Batchmodus.pdf

To show the differences in the transformations BETA2007 and BWTA2017, a grid with distances of 1km was created and transformed.

• bw_grid_1km_000.utm original grid in UTM coordinates, within the polygon of the open data set of Baden-Württemberg: Landesgrenze (ZIP-Archiv mit SHAPE-Dateien, ETRS89/UTM, Stand 12.2017) (data source = Datenquelle: LGL, www.lgl-bw.de).
• bw_grid_1km_000.etrs89.zip ETRS89 geographical coordinates (from UTM)
• bw_grid_1km_000.etrs89_via_BWTA2017_to_gk3.zip (Gauß-Krüger zone 3 [GK3] coordinates from ETRS89 geographical coordinates), transformation grid BWTA2017
• bw_grid_1km_000.etrs89_via_BWTA2017_to_gk3_via_BETA2007_to_etrs89.zip (ETRS89 from GK3), transormation grid BETA2007
• bw_grid_1km_000.utm.offset.zip UTM coordinate differences, see attributes for UTM coordinates and differences diffr=$x-"field_1", diffh=$y-"field_2"

Transformations were computed with ogr2ogr and the bash script tf_beta2007.sh included in this repository.

tf_beta2007.sh [-r] [-n nadgridsfile] [-v] infile.shp [outfile.shp]
 -r reverse transformation
 -n nadgridsfile (default: /usr/share/proj/BETA2007.gsb)

For reference and reusage, the resulting ogr2ogr commands used were:

ogr2ogr -s_srs EPSG:4258 -t_srs '+proj=tmerc +lat_0 =0 +lon_0=9 +x_0=3500000 +y_0=0 +k=1.000000 +ellps=bessel +units=m +nadgrids=/usr/share/proj/BWTA2017.gsb +wktext ' -f 'ESRI Shapefile' bw_grid_1km_000.etrs89_via_BWTA2017_to_gk3.shp bw_grid_1km_000.etrs89.shp

ogr2ogr -s_srs '+proj=tmerc +lat_0 =0 +lon_0=9 +x_0=3500000 +y_0=0 +k=1.000000 +ellps=bessel +units=m +nadgrids=/usr/share/proj/BETA2007.gsb +wktext ' -t_srs EPSG:4258 -f 'ESRI Shapefile' bw_grid_1km_000.etrs89_via_BWTA2017_to_gk3_via_BETA2007_to_etrs89.shp bw_grid_1km_000.etrs89_via_BWTA2017_to_gk3.shp

A QGIS project was used for the visualisation: bw_grid000.qgs.
The project contains a Map for PDF (and other file type) exports.

Differences between Transformations visualised
BETA2007 (Germany) - BWTA2017 (Baden-Württemberg)

• plotted at grid points of 1km distance
• dot color denotes direction
• dot size the difference (1km diameter ~ 100mm)
• lines: length and direction denote destortion

The files and images are licensed: BETA2007 - BWTA2017 differences by
github/Marwe
is licensed under a
Creative Commons Attribution 4.0 International License