[Proj] DHDN / Gauss Krueger to WGS84

Oliver Eichler oliver.eichler at dspsolutions.de
Thu Sep 20 11:52:10 EDT 2007

Hi Frank
> pjgaukru = pj_init_plus("+init=epsg:31467");
> pjwgs84 = pj_init_plus("+init=epsg:4326");
> //???
> double z = 0;
What is the z parameter for? Height?

> I would add that epsg:31467 expands as:
> +proj=tmerc +lat_0=0 +lon_0=9 +k=1.000000 +x_0=3500000 +y_0=0
> +ellps=bessel +datum=potsdam +units=m +no_defs
> Note that this definition is using +datum=potsdam which expands to:
>   +ellps=bessel +towgs84=606.0,23.0,413.0
That should be ok. These are maps from "Bayerisches
Landesvermessungsamt". Hope they know what they are doing.
> This may or may not be the best datum shift parameters for your area of
> work.  You may need to research a better local shift.
Does that mean that the shift parameters depend on the location within
the map? Or that the whole map might have some kind of bad offset
produced by a bad projection?

And how would I get better shift parameters? Is there a tutorial somewhere?



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