[Qgis-user] bessel ellipsoid 1841

[Barend Köbben]

FYI, the proj string does have a datum, one based on the Bessel ellipsoid
(which is a datum), but I agree with giovanni that the proj=longlat is
unlikely to be correct for your map. Neighbouring Netherlands uses the
Bessel datum, and a double stereographic projection (It's epsg:28992). But
also it is doubtful that was used in the 19th century (sorry). Nowadays
Germany uses Gauss-Kruger, Münsterland would be in EPSG Projection 31466 -
DHDN / 3-degree Gauss-Kruger zone 2 ...



--
Barend Köbben
ITC - University of Twente, Faculty of Geo-Information
Science and Earth Observation
PO Box 217, 7500AE Enschede (The Netherlands)
+31-(0)53 4874 253



On 26-09-11 23:02, "G. Allegri" <giohappy at gmail.com> wrote:

>It's quite unlikely that an earth centred datum has been used for your
>map, and the 4004 should only be used when the datum is unkonwn and we
>suppose that the ellipsoid origin is the earth centre... yet I don't know
>what the geodetic reference(s) was used in Germany along the 19th century.
>
>giovanni
>
>
>
>2011/9/26 Torsten Lange <tlange at gwdg.de>
>
>
>Hello,
>
>I have a historical map from 1855 from the Muensterland Basin, Germany.
>The
>map shows geographic coordinates, thus my colleague said most likely it's
>Bessel 1841 ellipsoid.
>
>QGis offers:
>Unknown datum based upon the Bessel 1841 ellipsoid EPSG:4004
>+proj=longlat +ellps=bessel +no_defs
>
>Why there is no datum? Shouldn't there be one?
>
>Thank you, Torsten
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