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Repository for proj datum grids (for use by PROJ 7 or later)
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Geoid models FIN2000 and FIN2005N00 #110

Open ktheijs opened 8 months ago

ktheijs commented 8 months ago

I noticed that there are some JSON files available to transform between Finnish vertical coordinate reference systems. fi_nls_n43_n60.json: N43 height -> N60 height fi_nls_n60_n2000.json: N60 height -> N2000 height

On the authority's website they also speak about a geoid model FIN2000 and FIN2005N00 to transform from ellipsoidal heights to N60 and N2000. (https://www.maanmittauslaitos.fi/en/asioi-verkossa/palveluiden-kayttoohjeet/paikkatietoikkuna/koordinaattimuunnos)

I can't find any of the files on their website, but can someone explain why the two JSON files are available and the geoid model is not? It it a licensing issue?

jjimenezshaw commented 8 months ago

Regarding the geoid models, I started working on them. What is missing is the transformation definition from ETRS89 in EPSG. I contacted @jratike80 from the MML, asking if they can add the missing transformations to EPSG. They are working on it (but I don't know how much is done).

ktheijs commented 8 months ago

Thank you @jjimenezshaw, that's great news! Are there any other geoids models that you are working on? (e.g. Turkey, Greece,...)

jjimenezshaw commented 8 months ago

As far as I know Turkey has a paid geoid model. It would be great if somebody from that country could ask to move to an open source model as it was done in Switzerland in 2021 o in Germany in 2023 (in both countries you had to pay to get and use the files. Now they are open and free and included in PROJ-data). Or maybe I'm wrong.

The last time I tried to research about Greece I did not find anything useful. It was too chaotic for me. Language was not helping. If anybody with some local knowledge/contacts could help, I am happy to include it (if possible).

I contacted the Latvian authorities. They publish a geoid model with CC-BY-4.0. However, updating EPSG to include "LKS-92 to Latvia 2000 height" is not in their plans because they are working in another geoid model for the new system LKS-2020. Should we include it without EPSG transformation (we have to create our own)? That's a question for other people in PROJ ;)

There is another model available as CC-BY-4.0 for Taiwan. I contacted the authorities (NLSC) about adding the transformation to EPSG, but I got no answer. Same question about including it as for Latvia.

Note: having the needed data (see below) it is very easy to me to add another geoid model. If any local person gathers all that information I am happy to implement it.