1954 - 1961 Data supplied by the British Hydrographic Dept. =========================== FOLLOWING PSMSL DOCUMENTATION ADDED 11-Jun-1991 Sembawang 555/051 RLR(1955) is 9.9m below TGBM =========================== FOLLOWING PSMSL DOCUMENTATION ADDED 12-Oct-2010 ACD 1954-1985 is 4.892m below TGBM. ACD 1986 onwards is 4.923m below TGBM. RLR (1955) is 9.9m below TGBM.