Add 5.878m to data 1967-1978 to refer to RLR (1967)
Add 5.740m to data 1979-1997 to refer to RLR (1967)
Add 5.634m to data 1998-2002 to refer to RLR (1967)
Add 5.924m to data 2003 - to refer to RLR (1967)
RLR (1967) is 11.2m below BM TG Pit
LLD = Land Levelling Datum
