law: Indian Ports Act, 1908
  41. Ascertainment of tonnage of vessel liable to port-dues
  
   
  In order to ascertain the tonnage of any vessel liable to pay
  
  port-dues the following rules shall be observed, namely
  (1) (a) If the vessel is a British registered vessel or a vessel
  
  registered under the Indian Registration of Ships Act, 1841 (10 of 1841), or
  
  the Indian Registration of Ships Act (1841) Amendment Act, 1850 (11 of 1850),
  
  or under any other law for the time being in force for the registration of
  
  vessels in 56[India], the conservator may require the owner or
  
  master of the vessel or any person having possession of her register to produce
  
  the register for inspection.
  (b) If the owner or master of such person
  
  neglects or refuses to produce the register or otherwise to satisfy the
  
  conservator as to what is the true tonnage of the vessel in respect of which
  
  the port-dues are payable, he shall be punishable with fine which may extend to
  
  one hundred rupees, and the conservator may cause the vessel to be measured,
  
  and the tonnage thereof to be ascertained, according to the mode of measurement
  
  prescribed by the rules for the time being in force for regulating the
  
  measurement of British vessels, and in such case the owner or master of the
  
  vessel shall also be liable to pay the expenses of the measurement.
  (2) If the vessel is not a British registered vessel or a vessel
  
  registered under the Indian Registration of Ships Act, 1841, (10 of 1841), or
  
  the Indian Registration of Ships Act (1841) Amendment Act, 1850 (11 of 1850),
  
  or under any other law for the time being in force for the registration of
  
  vessels in 56[India], and the owner or master thereof fails to
  
  satisfy the conservator as to what is her true tonnage according to the mode of
  
  measurement prescribed by the rules for the time being in force for regulating
  
  the measurement of British vessels, the conservator shall cause the vessel to
  
  be measured and the tonnage thereof to be ascertained according to the mode
  
  aforesaid and in such case owner or master of the vessel shall be liable to pay
  
  the expenses or the measurement.
  (3) If the vessel is a vessel of which the tonnage cannot be
  
  ascertained according to the mode of measurement mentioned in clauses (1) and
  
  (2), the tonnage of the vessel shall be determined by the conservator on such
  
  an estimate as may seem to him to be just.