[Proj] PROJ: Further help with the swisstopo NTv2 grid shift ?

Melita Kennedy mkennedy2 at earthlink.net
Wed Feb 1 07:31:03 EST 2012

One method would be to calculate the CH1903+ to WGS84 offset for each NTv2 grid point, concatenate them with the offsets from the original file and build a new NTv2 file. EPSG lists a 1m transformation from CH1903+ to WGS84, do a code search for 1676 at http://www.epsg-registry.org. 


Disclaimer: I'm a member of the subcommittee that maintains the dataset.

>Date: Tue, 31 Jan 2012 17:33:46 +0100
>From: Sandro Santilli <strk at keybit.net>
>Subject: [Proj] Further help with the swisstopo NTv2 grid shift ?
>To: proj at lists.maptools.org
>Now that I understood how to use the NTv2 gridshift file provided
>by swisstopo (chaining transforms) I'd like to evaluate feasibility
>of producing a _new_ NTv2 gridshift file going straight to WGS84
>latlong rather than CH1903+ latlong.
>How could I proceed to compute the shift ?

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