Projection - once again

Question

I have a shape file with nature preservation areas (Biosphärenreservate) in Germany. I think the projection must be something like gauss-krüger zone 4 Pulkovo or something like that. When I reproject it to UTM-33N WGS84 it reprojects but is not exactly accurate. The borders don't quite match my other shape (the other file)

http://www.projektidee.org/images/extern/biosph-res-2010.prj.zip http://www.projektidee.org/images/extern/gebiet_UTM33.dbf.zip

Could anyone here help me with that problem. That would be nice!

best regards desputin

Answer 1

Opening up biosph-res-2010.prj in a text editor, I get:

PROJCS["DHDN_3_Degree_Gauss_Zone_3",
  GEOGCS["GCS_Deutsches_Hauptdreiecksnetz",
    DATUM["D_Deutsches_Hauptdreiecksnetz",
    SPHEROID["Bessel_1841",6377397.155,299.1528128]],
    PRIMEM["Greenwich",0.0],
    UNIT["Degree",0.0174532925199433]],
  PROJECTION["Gauss_Kruger"],
  PARAMETER["False_Easting",3500000.0],
  PARAMETER["False_Northing",0.0],
  PARAMETER["Central_Meridian",9.0],
  PARAMETER["Scale_Factor",1.0],
  PARAMETER["Latitude_Of_Origin",0.0],
  UNIT["Meter",1.0]]

So you were almost right - I get the (apparently deprecated) DHDN / 3-degree Gauss zone 3 (EPSG:31463)

What I think your problem is, is not one of projection, but of digitization and simplification. Overlaying biosph-res-2010 (red) and gebiet_UTM33 (blue) on Google aerial imagery gives me this:

So your biosphärenreservate line matches the coast quite closely, but the blue line has far fewer points, and isn't shifted by a uniform amount. So the quality of your data is questionable rather than your projection.