[Proj] Help with use of swisstopo NTv2 grid shift ?

[Mikael Rittri]

Sandro Santilli wrote:

> It would surely help if I had an official set of points in CH1903
> and CH1903+ to test my conversions against...

You can find test points in Chapter 7 of 

"Formulas and constants for the calculation of the Swiss conformal
cylindrical projection and for the transformation between coordinate
systems", 

http://www.swisstopo.admin.ch/internet/swisstopo/en/home/topics/survey/sys/refsys/switzerland.parsysrelated1.37696.downloadList.97912.DownloadFile.tmp/swissprojectionen.pdf

There are five positions that are expressed in various Swiss systems.
Unfortunately, CH1303 LongLat is not one of them, but LV03 is included,
which I think is what EPSG calls "CH1903 / LV03" (EPSG:21781). So it is
possible to find out the CH1903 LongLat coordinates via Proj.4, like this

C:\Windows\system32>proj +init=epsg:21781 -I
602030.680 191775.030
7d27'58.413"E   46d52'42.269"N
617306.300 268507.300
7d40'10.545"E   47d34'6.387"N
776668.105 265372.681
9d47'8.443"E    47d31'0.107"N
497313.292 145625.438
6d6'10.014"E    46d27'19.25"N
722758.810 87649.670
9d1'20.596"E    45d55'49.755"N

Which you can compare with the corresponding CH1903+ LongLat from Chapter 7:

7 27 58.416328	46 52 42.269284 
7 40 10.574820	47 34  6.404965
9 47  8.465989	47 31  0.092644 
6  6  9.983811	46 27 19.272743 
9  1 20.606368	45 55 49.707052 

Hope this helps,

Mikael Rittri
Carmenta
Sweden
http://www.carmenta.com

-----Original Message-----
From: proj-bounces at lists.maptools.org [mailto:proj-bounces at lists.maptools.org] On Behalf Of Sandro Santilli
Sent: Monday, January 23, 2012 6:48 PM
To: PROJ.4 and general Projections Discussions
Subject: Re: [Proj] Help with use of swisstopo NTv2 grid shift ?

[ see http://lists.maptools.org/pipermail/proj/2012-January/006070.html ]