[OSRS-PROJ] PROJ4 and datums

[Markus Neteler]

On Mon, Apr 03, 2000 at 11:33:45AM -0400, Gerald I. Evenden wrote:
> Except for the North American Datum (NAD), PROJ does
> not support datum conversions.  PROJ is system for
> cartographic projections only.  *nad2nad* was included
> in the PROJ distribution as an example of how to use
> the PROJ lib.
> 
> Jerry Evenden and the low riders: Katie and Daisy-Mae
> gevenden at capecod.net  http://www.capecod.net/~gevenden

Yes, I understand. But my question was more related to 
following, more general, point:

Do I need datum conversion if reprojecting a map
from UTM/WGS84 to Transverse Mercator/Bessel?
The German system is based on Potsdam-Datum, the
UTM datum I don't know.

As nad2nad is existing, the datum conversion seems
to be important.

Kind regards

 Markus Neteler



> -----Original Message-----
> From: Markus Neteler <neteler at geog.uni-hannover.de>
> To: osrs-proj at remotesensing.org <osrs-proj at remotesensing.org>
> Date: Monday, April 03, 2000 10:40 AM
> Subject: [OSRS-PROJ] PROJ4 and datums
> 
> 
> >Hi all,
> >
> >concerning the datum problem and PROJ4 I have
> >a question (as PROJ4 is included in GRASS 5):
> >
> >Say, I have a map in UTM/WGS84. Using the
> >map projection modules of GRASS (r.proj/v.proj)
> >I can project the map to the German
> >"Gauss-Krueger-System" (Transverse Mercator,
> >Bessel Ellipsoid).
> >
> >But what about datum conversion? Gauss-Krueger
> >is based on Potsdam-Datum (near Berlin).
> >
> >BTW: Interesting page about nearly all European
> >map systems (by Stefan A. Vosser):
> >http://www.geocities.com/CapeCanaveral/1224/mapref.html
> >
> >especially: "Map Projections" there.
> >
> >I am not familiar with this datum stuff, any
> >hints to clear the situation are welcome.
> >>From former comments I learned that PROJ4 does
> >not support datum conversion, but maybe nad2nad
> >to be extended to support conversions outside U.S.?
> >Please excuse if this is a stupid questions...
> >
> >Kind regards
> >
> > Markus Neteler
> 
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