Fundamental information about spatial data transformation: Proj4
Compilation of world-wide transformation parameters: EPSG
Open source utility for spatial data transformation: GDAL
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EPSG-transformation parameters
MGI (Militaergeographisches Institut) alias Hermannskogel - Austria:

  MGI to WGS84 (7-parameter transformation, accuracy of 1.5 meter)
   X-axis translation  577,326 meter
   Y-axis translation  90,129   meter
   Z-axis translation  463,919 meter
   X-axis rotation   5,137   arc-second
   Y-axis rotation   1,474   arc-second
   Z-axis rotation   5,297   arc-second
   scale difference  2,4232 parts per million

Please check always EPSG for newer version of transformation parameters!

For raster transformation by gdal_translate/gdalwarp or vector transformation by ogr2ogr
you have to include

   TOWGS84[577.326,90.129,463.919,5.137,1.474,5.297,2.4232]

into the projection parameters of spatial data in Austria. You can also use the following WKT-files:  

            Austria_BMN_MGI_M28.prj        Bundesmeldenetz Meridian 28
            Austria_BMN_MGI_M31.prj        Bundesmeldenetz Meridian 31
            Austria_BMN_MGI_M34.prj        Bundesmeldenetz Meridian 34
            Austria_GK_MGI_M28.prj          Gauss-Krueger Meridian 28
            Austria_GK_MGI_M31.prj          Gauss-Krueger Meridian 31
            Austria_GK_MGI_M34.prj          Gauss-Krueger Meridian 34
            Austria_MGI_Lambert.prj          Lambert

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For Germany you can use the following WKT-file:

            DHDN_zone4.prj                       DHDN Zone 4 (e.g. for Bavaria)

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For Italy you can use the following WKT-files:

            Italy_montemario.prj                Italy Gauss-Boaga (northern part of Italy)

            italy_etrf1989.prj                      Italy ETRF 1989 (northern part of Italy)                    

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example for raster transformation with gdal:

(for syntax and supported formats please see the gdal-manuals)

source: ortho.tif/ortho.tfw in Bundesmeldenetz M28
target:  Gauss-Krueger M31

=> assign projection information for Bundesmeldenetz M28 to raster data

gdal_translate -of GTiff -a_srs ESRI::Austria_BMN_MGI_M28.prj //

-co "TFW=YES" -co "COMPRESS=LZW" ortho.tif orthoBMN_M28.tif

=> raster transformation from Bundesmeldenetz M28 to Gauss-Krueger M31

gdalwarp -s_srs ESRI::Austria_BMN_MGI_M28.prj //

-t_srs ESRI::Austria_GK_MGI_M31.prj -of GTiff //

-co "TFW=YES" orthoBMN_M28.tif orthoGK_M31.tif

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example for transformation with ogr2ogr:

(for syntax and supported formats please see the ogr-manuals)

source: shapefileBMNM28.shp in Bundesmeldenetz M28
target:  Bundesmeldenetz M34

ogr2ogr -s_srs ESRI::Austria_BMN_MGI_M28.prj //

-t_srs ESRI::Austria_BMN_MGI_M34.prj //

shapefileBMNM34.shp shapefileBMNM28.shp
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