Add 3.448m to data values 1978-1983 to refer to RLR (1986)
Add 3.445m to data values 1984-1990 to refer to RLR (1986)
Add 3.443m to data values 1991 onwards to refer to RLR 91986)
RLR (1986) is 12.1m below BM Monbetu
