AW: [Proj] DHDN / Gauss Krueger to WGS84

[Dean Mikkelsen]

Hi Oliver,
 
I forgot to add the following:
 
The parameters for a datum shift (dx, dy, dz, rx, ry, rz, etc.) between ETRS89 and WGS84 are not constant, due to the movement of the Eurasian geophysical plate with respect to WGS84. The differences between both datums can grow by several centimetres a year. Currently they are a couple of decimetres in difference. For many applications, these differences are not relevant. Coordinates or positions in WGS84 have usually been obtained by GPS and this results in an accuracy at the level of several metres. However, satellite positioning techniques continuously improve in accuracy, also without using differential stations. So the differences between the datum's will grow. Note that many nations are using WGS84 to define boundaries nowadays - so WGS84 is relevant.
 
In your case and for your application, I do believe you will be fine using ETRS89.
 
Cheers,
Dean
 


----- Original Message -----
From: Dean Mikkelsen <dcmikkelsen at shaw.ca>
Date: Friday, September 21, 2007 10:26 am
Subject: Re: AW: [Proj] DHDN / Gauss Krueger to WGS84
To: oliver.eichler at dspsolutions.de, "PROJ.4 and general Projections Discussions" <proj at lists.maptools.org>
Cc: "PROJ.4 and general Projections Discussions" <proj at lists.maptools.org>, dcmikkelsen at shaw.ca

> Hi Oliver,
>  
> No question is ever dumb. If no one ever asks, no one can ever learn.
>  
> A technical definition from Wikipedia states:
>  
> "The European Terrestrial Reference System 1989, usually 
> referred to as ETRS89, is a three-dimensional geodetic frame of 
> reference - a mapping coordinate system used as the standard 
> high accuracy system for GPS in Europe.
>  
> It coincided with the World Geodetic System 1984 in 1989, hence 
> the name, and is based on the same GRS80 ellipsoid. Unlike WGS84 
> or ITRS it is centred on Europe and diverges from them with the 
> movements of the tectonic plates associated with this landmass."
>  
> Please see: http://en.wikipedia.org/wiki/ETRS89 for ETRS89
>                  and  http://en.wikipedia.org/wiki/World_Geodetic_System_1984 for WGS84
>  
> These are some pretty good description of some systems used in 
> Geodesy. 
> Cheers,
> Dean
>  
>  
> 
> ----- Original Message -----
> From: Oliver Eichler <oliver.eichler at dspsolutions.de>
> Date: Friday, September 21, 2007 8:59 am
> Subject: Re: AW: [Proj] DHDN / Gauss Krueger to WGS84
> To: "PROJ.4 and general Projections Discussions" 
> <proj at lists.maptools.org>
> > uwe.schmitz at lverma.nrw.de wrote:
> > > please take a look at 
> > > 
> > 
> http://crs.bkg.bund.de/crseu/crs/descrtrans/BeTA/de_dhdn2etrs_beta.php>> > There you will find information about a "standard" solution 
> > > for your problem. The documentation gives a brief example
> > > for using PROJ.4. (I think, the german language isn't a problem
> > > for you :-)).
> > >
> > > If you have any problems, please let me know.
> > >
> > >   
> > Hi Uwe
> > 
> > Ok, had a look at it. Maybe it's a dump question (I am really not
> > professional in this area) but as my target datum is WGS84 
> > shouldn't I
> > use different shift factors than for ETRS89?
> > 
> > Or is the shift from ETRS89 to WGS84 independent from the actual
> > location? Google gives me the impression that it is.
> > 
> > Oliver
> > _______________________________________________
> > Proj mailing list
> > Proj at lists.maptools.org
> > http://lists.maptools.org/mailman/listinfo/proj
> > 
> 
> Dean C. Mikkelsen, B.Sc., P.Eng.
> Terra ETL Ltd.
> Mobile/Cellphone: +1 250 361 6672
> E-mail: dcmikkelsen at shaw.ca
> 
> 

Dean C. Mikkelsen, B.Sc., P.Eng.
Terra ETL Ltd.
Victoria, B.C., Canada
Phone: +1 (250) 361-6672
http://www.terraetl.com

Consulting in Geodesy & GIS  for the Natural Resources
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