Add 7.78m to data values 1992 to 1993 to refer to RLR (1997)
Add 7.71m to data values 1994 to Oct.1998 to refer to RLR (1997)
Add 7.765m to data values Nov.1998 to Oct. 2005 to refer to RLR (1997)
Add 7.585m to data values Nov.2005 onwards to refer to RLR (1997)
RLR (1997) is 10.7m below BM A
