Add 5.535m to data values up to 1972 to refer to RLR (1963)
Add 6.057m to data values 1973-1993 to refer to RLR (1963)
Add 5.875m to data values 1994-1997 to refer to RLR (1963)
Add 5.70m to data values 1998-2002 to refer to RLR (1963)
Add 5.85m to data values 2003 onwards to refer to RLR (1963)
RLR (1963) is 10.053m below BM PN 1
LLD = Land Levelling Datum
