Add 3.792m to data values 1954-1957 to refer to RLR (1989)
Add 3.492m to data values 1958-1965 to refer to RLR (1989)
Add 3.482m to data 1965-1975 to refer to RLR (1989)
Add 3.412m to data 1976-  to refer to RLR (1989)
RLR (1989) is 12.2m below BM 72831
