Swiss Grid Systems

[Irwin Scollar]

Swiss Grid Systems

May I suggest that interested participants in this discussion thread open:

http://www.swisstopo.admin.ch/internet/swisstopo/en/home/apps/calc.html

and on the documentation entry on the right click on Reference system
CH as well as on the Transformation CH1903<->WGS84  for the official
version dated 19.11.2008?

They are available in English, German and French.

For those requiring higher accuracy for non-GIS geodetic
purposes,  browse through the superb pages of the Swisstopo site for
the finest documentation I have seen anywhere.

http://www.swisstopo.admin.ch/internet/swisstopo/en/home.html

The NTv2 grid data is available in the topic Transformation data and
formulae CHENyx06 of March 2007. See for example

http://www.swisstopo.admin.ch/internet/swisstopo/de/home/products/downloads/software.html 
for much more.

Irwin Scollar

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[Paul Kelly]

On Sun, 12 Jul 2009, Irwin Scollar wrote:

> Swiss Grid Systems
>
> May I suggest that interested participants in this discussion thread open:
>
> http://www.swisstopo.admin.ch/internet/swisstopo/en/home/apps/calc.html

Thanks, that was quite helpful. It also led me to the discovery that
exactly the same thing was being discussed on *this* list just under 8
years ago:
<http://lists.maptools.org/pipermail/proj/2001-September/000248.html>

In summary, all the sources seem to suggest that the old 7-parameter
transformation given in the Grids & Datums column was simply inaccurate
and has been recalculated more accurately since it was originally
publicised. I'm still curious as to the subtle difference between the
3-parameter transformation given in the column and that that is now
generally accepted, but in my mind anyway things are a lot clearer -
thanks.

Paul
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