Tonnage
Gross tonnage is a measure of the internal capacity of the ship and net
tonnage is intended to give an idea of the earning or useful capacity of the
ship. Various port dues and other charges may be assessed on the gross and
net tonnages. It will be noted from the previous chapter that the gross tonnage
of a ship may determine its requirement to comply with international
standards.
International Convention on Tonnage Measurement
of Ships 1969
An International Conference on Tonnage Measurement was convened
by IMO in 1969 with the intention of producing a universally acceptable
system of tonnage measurement. The International Convention on Tonnage
Measurement of Ships 1969 was prepared at this conference and this
convention came into force on the 8th July, 1982. All ships constructed on
or after that date were measured for tonnage in accordance with the 1969
Convention. Ships built prior to that date were if the owner so desired permitted
to retain their existing tonnages for a period of 12 years from that
date, i.e. all ships were required to be measured in accordance with the
1969 Convention by 18th July, 1994.
Tonnages
GROSS TONNAGE The gross tonnage (GT) is determined by the following
formula:
where
K1=0.2+0.02 log10 V
V=total volume of all enclosed spaces in cubic metres.