Tonnage Convention 1969
A4. Other IMO and ILO conventions and codesDefinition
International Convention on Tonnage Measurement of Ships, defining GT and NT.
The International Convention on Tonnage Measurement of Ships, 1969, created the single universal system for measuring gross tonnage (GT) and net tonnage (NT) using formulae based on total enclosed volume. It entered into force on 18 July 1982 and replaced the divergent national systems, giving each ship one GT figure used to trigger thresholds across SOLAS, MARPOL, MLC, and port and canal dues.
Source: Tonnage Convention 1969, in force 18 July 1982