On 2020-05-08 18:01, Greg Troxel wrote:
> I think we now know that the existing datums don't differ much from WGS84
> except Belgium, and given the EVRF2007 datum, it seems clear that Belgium now
> will have that and the old one, differing by 2m.
> Hence the thing we need to know, we don't, in this case.
Depends how you define "much". According to this info on Wikipedia
(sorry that it is in Dutch), the French also have their own datum, which
is TAW-1.82m, which works out to NAP-0.50m.
https://nl.wikipedia.org/wiki/Tweede_Algemene_Waterpassing
A little light reading for Greg: "The transformation of GPS into NAP
heights: Combining NAP, GPS and geoid heights to compute a height
reference surface for the Netherlands"
https://repository.tudelft.nl/islandora/object/uuid%3Ae661fcdd-6fe8-46e9-b5ea-51dabbd89175
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