EPSG:31254 to WGS84 Transformation Parameters

Question

The official transformation parameters from EPSG:31254 to WGS84 are:

towgs84=577.326,90.129,463.919,5.137,1.474,5.297,2.4232 (EPSG:1618)

(defined here and used by ArcGIS MGI_To_WGS_1984_3 transformation method as well as in the EPSG:31254 definition used by QGis 2.18.1)

GeoServer 2.11.0 on the other hand uses the following transformation parameters in its EPSG:31254 definition:

TOWGS84[601.705, 84.263, 485.227, 4.7354, -1.3145, -5.393, -2.3887].

If I provide GeoServer with an alternate version of EPSG:31254 by using the epsg_overrides.properties file - using the EPSG:1618 transformation parameters - the layer is displayed in the wrong position (way off).

Question:

Why does GeoServer use these transformation parameters and not the official ones, and where does it get them from?

Why don't the official parameters work with GeoServer?

Answer 1

The values taken by Geoserver are valid only for Steiermark: http://epsg.io/1024

All other PROJ/GDAL based software uses the countrywide values: http://epsg.io/1618

Note that the first uses Coordinate Frame Rotation, while the second uses Position Vector Transformation. The difference is in the sign of the rotation and scale parameter values (4 to 7).