[Gdal-dev] ogr2ogr with reprojecting: DHDN to MGI Austria

[Helmut Kudrnovsky]

hi,

i have a question about ogr2ogr from shape-file to shape-file with reprojecting (fwtools 1.0.9 on win xp).

ogr2ogr -f "ESRI Shapefile" -s_srs natura2000.prj -t_srs Austria_BMN_MGI_M31.prj target.shp source.shp

both shape-files have included a prj-file, but without an TOWGS84-parameter. 

from an earlier question on this list i have learned about the importance of the TOWGS84-parameter for a correct reprojecting. 

so i searched epsg (in C:\Programme\FWTools1.0.9\proj_lib\epsg) for the missing value; for the target-srs i found the TOWGS84-parameter and included it into the -t_srs Austria_BMN_MGI_M31.prj ( i hope in a correct way). but for the source-srs i couldn't find anything in epsg. 

my question: do i need also for the source an TOWGS84-parameter? if yes, do you have maybe a hint for me where i can find this?

-s_srs natura2000.prj

PROJCS["Germany_Zone_4",
GEOGCS["GCS_Deutsches_Hauptdreiecksnetz",
DATUM["D_Deutsches_Hauptdreiecksnetz",
SPHEROID["Bessel_1841",6377397.155,299.1528128]],
PRIMEM["Greenwich",0.0],
UNIT["Degree",0.0174532925199433]],
PROJECTION["Transverse_Mercator"],
PARAMETER["False_Easting",4500000.0],
PARAMETER["False_Northing",0.0],
PARAMETER["Central_Meridian",12.0],
PARAMETER["Scale_Factor",1.0],
PARAMETER["Latitude_Of_Origin",0.0],
UNIT["Meter",1.0]]

epsg source
# DHDN / Gauss-Kruger zone 4
<31468> +proj=tmerc +lat_0=0 +lon_0=12 +k=1.000000 +x_0=4500000 +y_0=0 +ellps=bessel +datum=potsdam +units=m +no_defs  <>

-t_srs Austria_BMN_MGI_M31.prj

PROJCS["Austria_BMN_MGI_M31",
GEOGCS["GCS_MGI",
DATUM["D_MGI",
SPHEROID["Bessel_1841",6377397.155,299.1528128],
TOWGS84[577.326,90.129,463.919,5.137,1.474,5.297,2.4232]],
PRIMEM["Greenwich",0.0],
UNIT["Degree",0.0174532925199433]],
PROJECTION["Transverse_Mercator"],
PARAMETER["False_Easting",450000.0],
PARAMETER["False_Northing",-5000000.0],
PARAMETER["Central_Meridian",13.33333333333333],
PARAMETER["Scale_Factor",1.0],
PARAMETER["Latitude_Of_Origin",0.0],
UNIT["Meter",1.0]]

epsg target
# MGI / M31
<31285> +proj=tmerc +lat_0=0 +lon_0=13.33333333333333 +k=1.000000 +x_0=450000 +y_0=0 +ellps=bessel +towgs84=577.326,90.129,463.919,5.137,1.474,5.297,2.4232 +units=m +no_defs  <>

with greetings from austria and thanks in advance
helli

oxoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxo
helmut kudrnovsky
internet: www.alectoria.at
__________________________________________________________________________
Erweitern Sie FreeMail zu einem noch leistungsstärkeren E-Mail-Postfach!		
Mehr Infos unter http://freemail.web.de/home/landingpad/?mc=021131