* All data (1843-1999) supplied to the PSMSL to NN, with the above corrections
assumed to have already been applied.  Data 2000 onwards supplied to TGZ.
RLR(2000) is defined to be 10.487m below TGBM  
For data 1843-1999 add 7.0m to all values to refer to RLR(2000) 
For data 2000-  add 1.98m to all values to refer to RLR(2000)
