AW: [Proj] DHDN / Gauss Krueger to WGS84

[support.mn at elisanet.fi]

Hello all!

We have solved this problem with moving plates by adding a simple date with the coordinates of WGS84. That way you can always go back to the original position of that particular date in WGS84 (or any). The WGS84 datum (with date)  will stay accurate for ever, since it is always possible to trace back where the plates were at that specific date.

latitude,
longitude,
(WGS84),
date

That's it. At the moment we don't need this feature, but it is there to be sure that the positions recorded will always stay accurate.

Regards Janne.

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> 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


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