[PROJ] Finnish KKJ with triangle-wise affine transformation

[Oskari Timperi]

Hi Even,

You working with NLS sounds really wonderful! This is great news :-)

Is there somewhere I could follow progress on this? Is there any way I could help to make this happen?

I agree with your comment about plugins. But still, sometimes they would be very handy. :-)

- Oskari

From: Even Rouault <even.rouault at spatialys.com>
Sent: keskiviikko 17. kesäkuuta 2020 14.05
To: proj at lists.osgeo.org
Cc: Oskari Timperi <oskari.timperi at novatron.fi>
Subject: Re: [PROJ] Finnish KKJ with triangle-wise affine transformation


Oskari,



> In many places we still need to support the old KKJ (EPSG:2393) system. The

> National Land Survey of Finland (Maanmittauslaitos) provides a TIN network

> and affine transformation for each triangle for converting between

> ETRS-TM35FIN and KKJ. This is the preferred and most accurate way to

> convert to and from KKJ. More information and the plain text data files can

> be found from NLS website though only in Finnish but you should be able to

> get the idea

> https://www.maanmittauslaitos.fi/kartat-ja-paikkatieto/asiantuntevalle-kayt

> tajalle/koordinaattimuunnokset

>

> My question is, is this kind of transformation something that could be

> implemented inside PROJ at some point in the future? I don't know if this

> kind of thing is used anywhere else so it might be that this has very

> little use outside of Finland.



I'm currently working with National Land Survey of Finland to bring those transformations into PROJ. So stay tuned. Should come in coming weeks / months. Triangulation-based transformations are likely of interest in other cases too as a number of grid-based transformations come initially from triangulations.



> If this isn't viable, are there any plans about plugin support for PROJ? It

> would be cool to be able to implement custom steps and represent them as

> part of the normal PROJ pipeline to implement special needs :-)



I can see pros & cons to a plugin approach. From a community point of view, plugins tend to "isolate" people. Sometimes what one thinks to be a custom need can be useful for others.



Even



--

Spatialys - Geospatial professional services

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