Marine Surveyors Lexicon

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Tonnage Computation Under 1969 Tonnage Convention


Before a ship can be registered with a signatory to the 1969 Tonnage Convention, it must be measured in accordance with the regulations of that Convention. The Convention consists of only seven regulations for establishing the gross and net tonnages of a ship. In addition to the resultant tonnages being necessary for identification of ships when registered, they are also used for the charging of port dues, but more importantly from the regulatory regime point of view, gross tonnage is used in imposing size limitations in SOLAS 74 and MARPOL 73/78. For example a dry cargo ship of 499 gross tonnage on international voyages would have to comply with Chapter IV (Radio Communications) and Chapter V (Safety of Navigation) only of SOLAS 74. It would also have to comply with requirements of the 1966 Load Line Convention (being in excess of 24 metres in length) and MARPOL 73/78 Annexes I, III, V and when entered into force, IV.