[PROJ] Swiss geoid file (now free)

[Elmar.Brockmann at swisstopo.ch]

Dear colleagues

Indeed, the CHENYX06 grids we provide use CC0: " A NTV2 grid data set for transforming to ETRS or to LV95 is distributed in our Shop under open data licence Creative Commons CC0." (https://www.swisstopo.admin.ch/en/knowledge-facts/surveying-geodesy/reference-frames/transformations-position.html ) 

Yesterday, March 1, swisstopo announces officially a wide data set as Open Government Data (OGD). Now, also all areal images, digital maps are open and can freely be used for private and commercial applications. The Geoid CHGeo2004 is also included. Further details: https://www.swisstopo.admin.ch/en/swisstopo/free-geodata.html 

The FAQs state under licence conditions:  The use of Creative Commons licences, as they are commonly and widely used today, is not compatible with the legal basis (GeoIG, GeoIV). swisstopo geodata is supplied with conditions of use which comply with the legal basis. The conditions of use allow free use for all purposes and oblige the user to indicate the source as "Source: Federal Office of Topography swisstopo" or "© swisstopo".

If it helps, we can assign a CC0 licence to the geoid grids.
Best regards

Elmar Brockmann



-----Ursprüngliche Nachricht-----
Von: PROJ <proj-bounces at lists.osgeo.org> Im Auftrag von Even Rouault
Gesendet: Montag, 1. März 2021 20:03
An: proj at lists.osgeo.org
Cc: proj <PROJ at lists.osgeo.org>
Betreff: Re: [PROJ] Swiss geoid file (now free)

Hi,

> -- License --

Agreed with Bas that they should really consider using a known license. From the rights and requirements they indicate, it would seem to me that CC-BY 4.0 would be a good fit.

> -- Source CRS --
> The geoid file is provided in
> https://www.swisstopo.admin.ch/en/knowledge-facts/surveying-geodesy/ge
> oid.ht ml in 4 different "flavors": LV95/LHN95, LV95/LN02, 
> ETRS89/LHN95,
> ETRS89/LN02 (I will now concentrate on LHN95, as LN02 is older).
> 
> LV95 (short version of "CH1903+ / LV95") is a projected CRS (EPSG:2056).
> The geographic system "under" it is CH1903+ (EPSG:4150) I was 
> expecting a version like "CH1903+/LHN95" (the Swiss geographic CRS 
> with the Swiss vertical CRS), but there is not AFAIK.
> 
> What should we include in PROJ-data?
> a) ETRS89/LHN95
> b) LV95/LHN95
> c) CH1903+/LHN95 computed from LV95/LHN95
> d) something else
> e) multiple of the above

No special opinion regarding this. Yes currently we'd have to derive a grid in geographic coordinates. We should ultimately provide a way of dealing with grids in projected coordinates (UK uses that too). Not necessarily a huge deal of work, but has to be done...

> -- Transformation --
> There is no such a transformation in EPSG like "ETRS89 to LHN95 
> height" or
> "LV95 to LHN95 height" or "CH1903+ to LHN95 height". I was considering 
> asking Swisstopo to "create" them (via a proper EPSG request), but, 
> which one(s)? (this is probably related to the previous question, I guess).

That's a bit their call, but yes it would be good to ask them to register the transformations with EPSG to make them more easily usable. I'm not sure if EPSG includes geoid-like grid transformations where the interpolation CRS is a projected one currently, so they might be only able to register the ETRS89 to
LHN95 height currently.

Even

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