Lighthouse Directory from Russ Rowlett is very useful for all of us lighthouse lovers. But often I see great differences for height of the tower and focal plane elevation from Open Sea Map.
For instance: Roscoff ! A1812.1 Russ: 24 and 24, Open Sea : 15 and 24 (seems realistic )
Or the beacons in sea: A1818, Russ :20 and 14, Open Sea : 8 and 14 (seems realistic ) and so on...
Agreed! It seems this could be different datums...