> I agree with Greg. Transformation is part of the metadata and not part of the 
> CRS.
> It is a good idea to include information on the transformation history in the 
> metadata, not only for height but also for horizontal coordinates. It would 
> help if software would do that automatically in a standardised way.

This explains why the Danish height system DVR90 is now in EPSG as a datum 
ensemble consisting of 

1. DVR90(2001), heights from levelling
2. DVR90(2002), based on 2002-geoid
3. DVR90(2013), based on 2013-geoid
4. DVR90(2023), based on 2023-geoid

By using the specific member of the ensemble you *can* communicate how those 
heights came to be. If you don't know (or don't care), you can just use the 
ensemble.

This is not a perfect solution but I think it is a good as it gets within the 
boundaries of current standards. And done this way the software can do this 
both automatically and standardised.

/Kristian
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