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Deadweight Tonnage refers to the carrying capacity of a vessel. Deadweight tonnage can be figured by taking the weight of a vessel which is not loaded with cargo and subtracting that figure from the weight of the loaded vessel.

Displacement Tonnage is the actual weight of a vessel. The term is expressed as a displacement weight in order to reflect the amount of water which is displaced by the vessel's hull. The draft of a vessel can then be used to determine the weight using markings on the hull called load lines

Vessel Draft refers to the distance between the vessel's waterline and the lowest point of the vessel, usually the keel. The draft will change if the vessel becomes heavier or lighter.Very simply, draft is the depth of a vessel at any given time.

Gross Tonnage is a measure of volume inside a vessel. This includes all areas from keel to funnel and bow to stern.

The means to calculate gross tonnage is laid out in the International Convention on Tonnage Measurement of Ships.

Measurement of the total interior volume of a vessel in cubic meters is multiplied in a formula by a second factor which is determined by the volume of the vessel.

The formula is:

K=0.2+0.02*log10(V)

Gross Tonnage (GT) = K*V

Where V = Interior volume of a vessel in cubic meters

Gross Tonnage is used to determine the number of crew, safety rules, registration fees, and port dues. It is the standard most often used to define a vessel.

Traffic is controlled in coastal waters and inland passages with marker buoys. Buoys in coastal areas are known as Lateral Markers, when found in traffic lanes they are known as channel markers. Both types of markers serve the same purpose. They guide a vessel through an area known to be safe for passage, and provide a traffic separation scheme similar to a road on land.

These “Rules of the Road” are very similar to those you follow while driving an automobile on land, so we will use that as an example when talking about marine traffic.

IALA A and IALA B

If you are driving a car in an overseas country it is sometimes necessary to drive on the opposite side of the road than you usually do. This is the same for ships, but fortunately there are only two schemes IALA A and IALA B. IALA stands for International Association of Lighthouse Authorities.

IALA A is used in Europe, some areas of Africa, most of Asia, plus Australia and New Zealand; IALA B is used in North America, South America, Japan, the Philippines, and Korea.

Traffic Marker Buoys

Marker buoys come in two colors, green and red. Red buoys mark one side of a traffic lane and green marks the other side. Think of the area in the middle as a road or highway. On land a road has painted stripes marking safe areas for travel; a solid line marks both sides of the road and is meant not to be crossed, think of the red and green buoys as these lines. A road has a line painted in the middle to divide traffic by direction; in a maritime environment the center divider is invisible. The separation line is exactly in the center of the marked course.

IALA A Rules

In Europe, Australia, New Zealand, plus parts of Africa and Asia the IALA A rules are in force. This means that when traveling you should keep the green buoy on the right or starboard side of the vessel.

The shape of the marker also gives you traffic information. A triangular or cone-shaped top indicates the marker should be kept on the starboard side of the vessel.

IALA B Rules

The IALA B traffic separation scheme is used in North and South America, Japan, the Philippines, and Korea. It is the opposite traffic flow of the IALA A scheme. This is like driving on the opposite side of the road while overseas.

In this case, while traveling keep the red buoy on the right or starboard side of the vessel.

The same triangular or cone-shaped top will be present on markers which should be kept on the starboard side of the vessel.

Both traffic patterns have the same rules when it comes to marker shape. A triangular marker is always kept on the starboard side of the vessel no matter if it is red or green. While markers to the port side of the vessel will be square or flat topped

Entering and Exiting Traffic Separation Schemes

When entering a traffic separation area, proceed with caution and be alert. This is like a highway on ramp for ships and smaller craft. At busy times many vessels will be trying to enter these lanes. Try to align your vessel in the direction of travel within the lane. Essentially extending the lane beyond the actual lane markers will help you smoothly transition from open waters to the traffic lane. The entrance to a traffic separation scheme is subject to rules of Right of Way.

The Right of Way is one of the most important parts of the Rules of the Road and needs to be understood completely for safe operation.

Sometimes automobile traffic in busy areas takes on a special set of rules that is different from standard operation, and is usually only understood by local drivers.

The same thing is true on the water. Local vessels like water taxis or tender boats might not follow these traffic lanes, this is not necessarily breaking the rules because the vessels need to operate outside the lanes to do their job.

Exiting a traffic scheme is similar to entering. If you are traveling out into open water it is best to extend your heading past the end of the final marker. If your vessel is large or slow moving, traffic behind your vessel might be eager to pass. Wait until traffic clears before changing your course because not all vessels will sound the proper horn signal when attempting to pass. Be careful, Right of Way is important, but avoiding collision is more important than being right.

You may need to exit a traffic lane before reaching the end of the marked passage to reach your destination. Buoys are marked with numbers like street numbers. Red buoys always have an even number and green are marked with odd numbers. Maneuvering between marker buoys is acceptable as long as it can be done safely. Check for traffic outside the lane and for any orange and white buoys marking obstructions. If the way is clear you may proceed.

If you must cross the oncoming lane of traffic, wait for an appropriate gap in traffic and turn a perpendicular course across the lane.

Keep other vessels in mind when slowing down or turning out of a lane. Ships have limited maneuverability at low speeds and take a long time to stop. If you cannot turn across a lane without obstructing traffic, exit on the opposite side and wait for traffic to clear then proceed across both lanes to your destination.

Traffic Lane Crossings

Where two traffic lanes cross there is a special marker buoy. It is striped horizontally with red and green bands. This is similar to an intersection of a primary and secondary road. The top band designates the primary traffic route and the lower band designates the secondary route. Right of Way rules govern how traffic flows at these crossings, primary and secondary designations do not determine which vessel may cross first.

Maritime Rules of the Road

All Vessels are Required to Follow the Rules of the Road. Traffic is Controlled by Lane Markers, Navigational Aids, and Right of Way. The Rules are a Basic skill of Seamanship and are Internationally Recognized. Understanding the Rules of the Road is Necessary for Safe Operation of Any Type or Size of Vessel in Any Waters.

International Convention on Tonnage Measurement of Ships, 1969

(London, 23 June 1969)

THE CONTRACTING GOVERNMENTS,

DESIRING to establish uniform principles and rules with respect to the determination of tonnage of ships engaged on international voyages;

CONSIDERING that this end may best be achieved by the conclusion of a Convention;

HAVE AGREED as follows:

Article 1

General obligation under the Convention

The Contracting Governments undertake to give effect to the provisions of the present Convention and the Annexes hereto which shall constitute an integral part of the present Convention. Every reference to the present Convention constitutes at the same time a reference to the Annexes.

Article 2

Definitions

For the purpose of the present Convention, unless expressly provided otherwise:

(1) "Regulations" means the Regulations annexed to the present Convention;

(2) "Administration" means the Government of the State whose flag the ship is flying;

(3) "international voyage" means a sea voyage from a country to which the present Convention applies to a port outside such country, or conversely. For this purpose, every territory for the international relations of which a Contracting Government is responsible or for which the United Nations are the administering authority is regarded as a separate country;

(4) "gross tonnage" means the measure of the overall size of a ship determined in accordance with the provisions of the present Convention;

(5) "net tonnage" means the measure of the useful capacity of a ship determined in accordance with the provisions of the present Convention;

(6) "new ship" means a ship the keel of which is laid, or which is at a similar stage of construction, on or after the date of coming into force of the present Convention;

(7) "existing ship" means a ship which is not a new ship;

(8) "length" means 96 per cent of the total length on a waterline at 85 per cent of the least moulded depth measured from the top of the keel, or the length from the fore side of the stem to the axis of the rudder stock on that waterline, if that be greater. In ships designed with a rake of keel the waterline on which this length is measured shall be parallel to the designed waterline;

(9) "Organization" means the Inter-Governmental Maritime Consultative Organization.

Article 3

Application

(1) The present Convention shall apply to the following ships engaged on international voyages;

(a) ships registered in countries the Governments of which are Contracting Governments;

(b) ships registered in territories to which the present Convention is extended under Article 20; and

(c) unregistered ships flying the flag of a State, the Government of which is a Contracting Government.

(2) The present Convention shall apply to:

(a) new ships;

(b) existing ships which undergo alterations or modifications which the Administration deems to be a substantial variation in their existing gross tonnage;

(c) existing ships if the owner so requests; and

(d) all existing ships, twelve years after the date on which the Convention comes into force, except that such ships, apart from those mentioned in (b) and (c) of this paragraph, shall retain their then existing tonnages for the purpose of the application to them of relevant requirements under other existing International Conventions.

(3) Existing ships to which the present Convention has been applied in accordance with sub-paragraph (2)(c) of this Article shall not subsequently have their tonnages determined in accordance with the requirements which the Administration applied to ships on international voyages prior to the coming into force of the present Convention.

Article 4

Exceptions

(1) The present Convention shall not apply to:

(a) ships of war; and

(b) ships of less than 24 metres (79 feet) in length.

(2) Nothing herein shall apply to ships solely navigating:

(a) the Great Lakes of North America and the River St. Lawrence as far east as a rhumb line drawn from Cap des Rosiers to West Point, Anticosti Island, and, on the north side of Anticosti Island, the meridian of longitude 63W;

(b) the Caspian Sea; or

(c) the Plate, Parana and Uruguay Rivers as far east as a rhumb line drawn between Punta Rasa (Cabo San Antonio), Argentina, and Punta del Este, Uruguay.

Article 5

Force majeure

(1) A ship which is not subject to the provisions of the present Convention at the time of its departure on any voyage shall not become subject to such provisions on account of any deviation from its intended voyage due to stress of weather or any other cause of force majeure.

(2) In applying the provisions of the present Convention, the Contracting Governments shall give due consideration to any deviation or delay caused to any ship owing to stress of weather or any other cause of force majeure.

Article 6

Determination of tonnages

The determination of gross and net tonnages shall be carried out by the Administration which may, however, entrust such determination either to persons or organizations recognized by it. In every case the Administration concerned shall accept full responsibility for the determination of gross and net tonnages.

Article 7

Issue of certificate

(1) An International Tonnage Certificate (1969) shall be issued to every ship, the gross and net tonnages of which have been determined in accordance with the present Convention.

(2) Such certificate shall be issued by the Administration or by any person or organization duly authorized by it. In every case, the Administration shall assume full responsibility for the certificate.

Article 8

Issue of certificate by another government

(1) A Contracting Government may, at the request of another Contracting Government, determine the gross and net tonnages of a ship and issue or authorize the issue of an International Tonnage Certificate (1969) to the ship in accordance with the present Convention.

(2) A copy of the certificate and a copy of the calculations of the tonnages shall be transmitted as early as possible to the requesting Government.

(3) A certificate so issued shall contain a statement to the effect that it has been issued at the request of the Government of the State whose flag the ship is or will be flying and it shall have the same validity and receive the same recognition as a certificate issued under Article 7.

(4) No International Tonnage Certificate (1969) shall be issued to a ship which is flying the flag of a State the Government of which is not a Contracting Government.

Article 9

Form of certificate

(1) The certificate shall be drawn up in the official language or languages of the issuing country. If the language used is neither English nor French, the text shall include a translation into one of these languages.

(2) The form of the certificate shall correspond to that of the model given in Annex II.

Article 10

Cancellation of certificate

(1) Subject to any exceptions provided in the Regulations, an International Tonnage Certificate (1969) shall cease to be valid and shall be cancelled by the Administration if alterations have taken place in the arrangement, construction, capacity, use of spaces, total number of passengers the ship is permitted to carry as indicated in the ship's passenger certificate, assigned load line or permitted draught of the ship, such as would necessitate an increase in gross tonnage or net tonnage.

(2) A certificate issued to a ship by an Administration shall cease to be valid upon transfer of such a ship to the flag of another State, except as provided in paragraph (3) of this Article.

(3) Upon transfer of a ship to the flag of another State the Government of which is a Contracting Government, the International Tonnage Certificate (1969) shall remain in force for a period not exceeding three months, or until the Administration issues another International Tonnage Certificate (1969) to replace it, whichever is the earlier. The Contracting Government of the State whose flag the ship was flying hitherto shall transmit to the Administration as soon as possible after the transfer takes place a copy of the certificate carried by the ship at the time of transfer and a copy of the relevant tonnage calculations.

Article 11

Acceptance of certificate

The certificate issued under the authority of a Contracting Government in accordance with the present Convention shall be accepted by the other Contracting Governments and regarded for all purposes covered by the present Convention as having the same validity as certificates issued by them.

Article 12

Inspection

(1) A ship flying the flag of a State the Government of which is a Contracting Government shall be subject, when in the ports of other Contracting Governments, to inspection by officers duly authorized by such Governments. Such inspection shall be limited to the purpose of verifying:

(a) that the ship is provided with a valid International Tonnage Certificate (1969); and

(b) that the main characteristics of the ship correspond to the data given in the certificate.

(2) In no case shall the exercise of such inspection cause any delay to the ship.

(3) Should the inspection reveal that the main characteristics of the ship differ from those entered on the International Tonnage Certificate (1969) so as to lead to an increase in the gross tonnage or the net tonnage, the Government of the State whose flag the ship is flying shall be informed without delay.

Article 13

Privileges

The privileges of the present Convention may not be claimed in favour of any ship unless it holds a valid certificate under the Convention.

Article 14

Prior treaties, conventions and arrangements

(1) All other treaties, conventions and arrangements relating to tonnage matters at present in force between Governments Parties to the present Convention shall continue to have full and complete effect during the terms thereof as regards:

(a) ships to which the present Convention does not apply; and

(b) ships to which the present Convention applies, in respect of matters for which it has not expressly provided.

(2) To the extent, however, that such treaties, conventions or arrangements conflict with the provisions of the present Convention, the provisions of the present Convention shall prevail.

Article 15

Communication of information

The Contracting Governments undertake to communicate to and deposit with the Organization:

(a) a sufficient number of specimens of their certificates issued under the provisions of the present Convention for circulation to the Contracting Governments;

(b) the text of the laws, orders, decrees, regulations and other instruments which shall have been promulgated on the various matters within the scope of the present Convention; and

(c) a list of non-governmental agencies which are authorized to act in their behalf in matters relating to tonnages for circulation to the Contracting Governments.

Article 16

Signature, acceptance and accession

(1) The present Convention shall remain open for signature for six months from 23 June 1969, and shall thereafter remain open for accession. Governments of States Members of the United Nations, or of any of the Specialized Agencies, or of the International Atomic Energy Agency, or parties to the Statute of the International Court of Justice may become Parties to the Convention by:

(a) signature without reservation as to acceptance;

(b) signature subject to acceptance followed by acceptance; or

(c) accession.

(2) Acceptance or accession shall be effected by the deposit of an instrument of acceptance or accession with the Organization. The Organization shall inform all Governments which have signed the present Convention or acceded to it of each new acceptance or accession and of the date of its deposit. The Organization shall also inform all Governments which have already signed the Convention of any signature effected during the six months from 23 June 1969.

Article 17

Coming into force

(1) The present Convention shall come into force twenty-four months after the date on which not less than twenty-five Governments of States the combined merchant fleets of which constitute not less than sixty-five per cent of the gross tonnage of the world's merchant shipping have signed without reservation as to acceptance or deposited instruments of acceptance or accession in accordance with Article 16. The Organization shall inform all Governments which have signed or acceded to the present Convention of the date on which it comes into force

(2) For Governments which have deposited an instrument of acceptance of or accession to the present Convention during the twenty-four months mentioned in paragraph (1) of this Article, the acceptance or accession shall take effect on the coming into force of the present Convention or three months after the date of deposit of the instrument of acceptance or accession, whichever is the later date.

(3) For Governments which have deposited an instrument of acceptance of or accession to the present Convention after the date on which it comes into force, the Convention shall come into force three months after the date of the deposit of such instrument.

(4) After the date on which all measures required to bring an amendment to the present Convention into force have been completed, or all necessary acceptances are deemed to have been given under sub-paragraph (b) of paragraph (2) of Article 18 in case of amendment by unanimous acceptance, any instrument of acceptance or accession deposited shall be deemed to apply to the Convention as amended.

Article 18

Amendments

(1) The present Convention may be amended upon the proposal of a Contracting Government by any of the procedures specified in this Article.

(2) Amendment by unanimous acceptance:

(a) Upon the request of a Contracting Government, any amendment proposed by it to the present Convention shall be communicated by the Organization to all Contracting Governments for consideration with a view to unanimous acceptance.

(b) Any such amendment shall enter into force twelve months after the date of its acceptance by all Contracting Governments unless an earlier date is agreed upon. A Contracting Government which does not communicate its acceptance or rejection of the amendment to the Organization within twenty-four months of its first communication by the latter shall be deemed to have accepted the amendment.

(3) Amendment after consideration in the Organization:

(a) Upon the request of a Contracting Government, any amendment proposed by it to the present Convention will be considered in the Organization. If adopted by a majority of two-thirds of those present and voting in the Maritime Safety Committee of the Organization, such amendment shall be communicated to all Members of the Organization and all Contracting Governments at least six months prior to its consideration by the Assembly of the Organization.

(b) If adopted by a two-thirds majority of those present and voting in the Assembly, the amendment shall be communicated by the Organization to all Contracting Governments for their acceptance.

(c) Such amendment shall come into force twelve months after the date on which it is accepted by two-thirds of the Contracting Governments. The amendment shall come into force with respect to all Contracting Governments except those which, before it comes into force, make a declaration that they do not accept the amendment.

(d) The Assembly, by a two-thirds majority of those present and voting, including two-thirds of the Governments represented on the Maritime Safety Committee and present and voting in the Assembly, may propose a determination at the time of its adoption that an amendment is of such an important nature that any Contracting Government which makes a declaration under sub-paragraph (c) of this paragraph and which does not accept the amendment within a period of twelve months after it comes into force, shall cease to be a party to the present Convention upon the expiry of that period. This determination shall be subject to the prior acceptance of two-thirds of the Contracting Governments.

(e) Nothing in this paragraph shall prevent the Contracting Government which first proposed action under this paragraph on an amendment to the present Convention from taking at any time such alternative action as it deems desirable in accordance with paragraphs (2) or (4) of this Article.

(4) Amendment by a conference:

(a) Upon the request of a Contracting Government, concurred in by at least one-third of the Contracting Governments, a conference of Governments will be convened by the Organization to consider amendments to the present Convention.

(b) Every amendment adopted by such a conference by a two-thirds majority of those present and voting of the Contracting Governments shall be communicated by the Organization to all Contracting Governments for their acceptance.

(c) Such amendment shall come into force twelve months after the date on which it is accepted by two-thirds of the Contracting Governments. The amendment shall come into force with respect to all Contracting Governments except those which, before it comes into force, make a declaration that they do not accept the amendment.

(d) By a two-thirds majority of those present and voting, a conference convened under sub-paragraph (a) of this paragraph may determine at the time of its adoption that an amendment is of such an important nature that any Contracting Government which makes a declaration under sub-paragraph (c) of this paragraph, and which does not accept the amendment within a period of twelve months after it comes into force, shall cease to be a Party to the present Convention upon the expiry of that period.

(5) The Organization shall inform all Contracting Governments of any amendments which may come into force under this Article, together with the date on which each such amendment will come into force.

(6) Any acceptance or declaration under this Article shall be made by the deposit of an instrument with the Organization which shall notify all Contracting Governments of the receipt of the acceptance or declaration.

Article 19

Denunciation

(1) The present Convention may be denounced by any Contracting Government at any time after the expiry of five years from the date on which the Convention comes into force for that Government.

(2) Denunciation shall be effected by the deposit of an instrument with the Organization which shall inform all the other Contracting Governments of any such denunciation received and of the date of its receipt.

(3) A denunciation shall take effect one year, or such longer period as may be specified in the instrument of denunciation, after its receipt by the Organization.

Article 20

Territories

(1) (a) The United Nations, in cases where they are the administering authority for a territory, or any Contracting Government responsible for the international relations of a territory, shall as soon as possible consult with such territory or take such measures as may be appropriate in an endeavour to extend the present Convention to that territory and may at any time by notification in writing to the Organization declare that the present Convention shall extend to such territory.

(b) The present Convention shall, from the date of receipt of the notification or from such other date as may be specified in the notification, extend to the territory named therein.

(2) (a) The United Nations, or any Contracting Government which has made a declaration under sub-paragraph (a) of paragraph (1) of this Article at any time after the expiry of a period of five years from the date on which the Convention has been so extended to any territory, may by notification in writing to the Organization declare that the present Convention shall cease to extend to any such territory named in the notification.

(b) The present Convention shall cease to extend to any territory mentioned in such notification one year, or such longer period as may be specified therein, after the date of receipt of the notification by the Organization.

(3) The Organization shall inform all the Contracting Governments of the extension of the present Convention to all territories under paragraph (1) of this Article, and of the termination of any such extension under the provisions of paragraph (2) stating in each case the date from which the present Convention has been or will cease to be so extended.

Article 21

Deposit and registration

(1) The present Convention shall be deposited with the Organization and the Secretary-General of the Organization shall transmit certified true copies thereof to all Signatory Governments and to all Governments which accede to the present Convention.

(2) As soon as the present Convention comes into force, the text shall be transmitted by the Secretary-General of the Organization to the Secretariat of the United Nations for registration and publication, in accordance with Article 102 of the Charter of the United Nations.

Article 22

Languages

The present Convention is established in a single copy in the English and French languages, both texts being equally authentic. Official translations in the Russian and Spanish languages shall be prepared and deposited with the signed original.

IN WITNESS WHEREOF the undersigned being duly authorized by their respective Governments for that purpose have signed the present Convention.

DONE at London this twenty-third day of June 1969.

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ANNEX 1

REGULATIONS FOR DETERMINING GROSS AND NET TONNAGES OF SHIPS

Regulation 1

General

(1) The tonnage of a ship shall consist of gross tonnage and net tonnage.

(2) The gross tonnage and the net tonnage shall be determined in accordance with the provisions of these Regulations.

(3) The gross tonnage and the net tonnage of novel types of craft whose constructional features are such as to render the application of the provisions of these Regulations unreasonable or impracticable shall be as determined by the Administration. Where the tonnage is so determined, the Administration shall communicate to the Organization details of the method used for that purpose, for circulation to the Contracting Governments for their information.

Regulation 2

Definition of terms used in the Annexes

(1) Upper Deck

The upper deck is the uppermost complete deck exposed to weather and sea, which has permanent means of weathertight closing of all openings in the weather part thereof, and below which all openings in the sides of the ship are fitted with permanent means of watertight closing. In a ship having a stepped upper deck, the lowest line of the exposed deck and the continuation of that line parallel to the upper part of the deck is taken as the upper deck.

(2) Moulded Depth

(a) The moulded depth is the vertical distance measured from the top of the keel to the underside of the upper deck at side. In wood and composite ships the distance is measured from the lower edge of the keel rabbet. Where the form at the lower part of the midship section is of a hollow character, or where thick garboards are fitted, the distance is measured from the point where the line of the flat of the bottom continued inwards cuts the side of the keel.

(b) In ships having rounded gunwales, the moulded depth shall be measured to the point of intersection of the moulded lines of the deck and side shell plating, the lines extending as though the gunwales were of angular design.

(c) Where the upper deck is stepped and the raised part of the deck extends over the point at which the moulded depth is to be determined, the moulded depth shall be measured to a line of reference extending from the lower part of the deck along a line parallel with the raised part.

(3) Breadth

The breadth is the maximum breadth of the ship, measured amidships to the moulded line of the frame in a ship with a metal shell and to the outer surface of the hull in a ship with a shell of any other material.

(4) Enclosed spaces

Enclosed spaces are all those spaces which are bounded by the ship's hull, by fixed or portable partitions or bulkheads, by decks or coverings other than permanent or movable awnings. No break in a deck, nor any opening in the ship's hull, in a deck or in a covering of a space, or in the partitions or bulkheads of a space, nor the absence of a partition or bulkhead, shall preclude a space from being included in the enclosed space.

(5) Excluded Spaces

Notwithstanding the provisions of paragraph (4) of this Regulation, the spaces referred to in sub-paragraphs (a) to (e) inclusive of this paragraph shall be called excluded spaces and shall not be included in the volume of enclosed spaces, except that any such space which fulfils at least one of the following three conditions shall be treated as an enclosed space:

- the space is fitted with shelves or other means for securing cargo or stores;

- the openings are fitted with any means of closure;

- the construction provides any possibility of such openings being closed:

(a) (i) A space within an erection opposite an end opening extending from deck to deck except for a curtain plate of a depth not exceeding by more than 25 millimetres (one inch) the depth of the adjoining deck beams, such opening having a breadth equal to or greater than 90 per cent of the breadth of the deck at the line of the opening of the space. This provision shall be applied so as to exclude from the enclosed spaces only the space between the actual end opening and a line drawn parallel to the line or face of the opening at a distance from the opening equal to one half of the width of the deck at the line of the opening (Figure 1 in Appendix 1).

(a) (ii) Should the width of the space because of any arrangement except by convergence of the outside plating, become less than 90 per cent of the breadth of the deck, only the space between the line of the opening and a parallel line drawn through the point where the athwartships width of the space becomes equal to, or less than, 90 per cent of the breadth of the deck shall be excluded from the volume of enclosed spaces (Figures 2, 3 and 4 in Appendix 1).

(a) (iii) Where an interval which is completely open except for bulwarks or open rails separates any two spaces, the exclusion of one or both of which is permitted under sub-paragraphs (a)(i) and/or (a)(ii), such exclusion shall not apply if the separation between the two spaces is less than the least half breadth of the deck in way of the separation (Figures 5 and 6 in Appendix 1).

(b) A space under an overhead deck covering open to the sea and weather, having no other connexion on the exposed sides with the body of the ship than the stanchions necessary for its support. In such a space, open rails or a bulwark and curtain plate may be fitted or stanchions fitted at the ship's side, provided that the distance between the top of the rails or the bulwark and the curtain plate is not less than 0.75 metres (2.5 feet) or one-third of the height of the space, whichever is the greater (Figure 7 in Appendix 1).

(c) A space in a side-to-side erection directly in way of opposite side openings not less in height than 0.75 metres (2.5 feet) or one-third of the height of the erection, whichever is the greater. If the opening in such an erection is provided on one side only, the space to be excluded from the volume of enclosed spaces shall be limited inboard from the opening to a maximum of one-half of the breadth of the deck in way of the opening (Figure 8 in Appendix 1).

(d) A space in erection immediately below an uncovered opening in the deck overhead, provided that such an opening is exposed to the weather and the space excluded from enclosed spaces is limited to the area of the opening (Figure 9 in Appendix 1).

(e) A recess in the boundary bulkhead of an erection which is exposed to the weather and the opening of which extends from deck to deck without means of closing, provided that the interior width is not greater than the width at the entrance and its extension into the erection is not greater than twice the width of its entrance (Figure 10 in Appendix 1).

(6) Passenger

A passenger is every person other than:

(a) the master and the members of the crew or other persons employed or engaged in any capacity on board a ship on the business of that ship; and

(b) a child under one year of age.

(7) Cargo Spaces

Cargo spaces to be included in the computation of net tonnage are enclosed spaces appropriated for the transport of cargo which is to be discharged from the ship, provided that such spaces have been included in the computation of gross tonnage. Such cargo spaces shall be certified by permanent marking with the letters CC (cargo compartment) to be so positioned that they are readily visible and not to be less than 100 millimetres (4 inches) in height.

(8) Weathertight

Weathertight means that in any sea conditions water will not penetrate into the ship.

Regulation 3

Gross tonnage

The gross tonnage (GT) of a ship shall be determined by the following formula:

GT = K₁V

where: V = Total volume of all enclosed spaces of the ship in cubic metres,

K₁ = 0.2 + 0.02log₁₀V (or as tabulated in Appendix 2).

Regulation 4

Net Tonnage

(1) The net tonnage (NT) of a ship shall be determined by the following formula:

NT = K₂V_c 4d² + K₃ (N₁ + N₂),

^3D 10

in which formula:

(a) the factor 4d² shall not be taken as greater than unity;

^3D

(b) the term K₂V_c 4d² shall not be taken as less than 0.25 GT; and

^3D

(c) NT shall not be taken as less than 0.30 GT, and in which:

V_c = total volume of cargo spaces in cubic metres,

K₂ = 0.2 + 0.02 log₁₀V_c (or as tabulated in Appendix 2),

K₃ = 1.25 (GT + 10,000)/10,000

D = moulded depth amidships in metres as defined in Regulation 2(2),

d = moulded draught amidships in metres as defined in paragraph (2) of this Regulation,

N₁ = number of passengers in cabins with not more than 8 berths,

N₂ = number of other passengers,

N₁ + N₂ = total number of passengers the ship is permitted to carry as indicated in the ship's passenger certificate; when N₁ + N₂ is less than 13, N₁ and N₂ shall be taken as zero,

GT = gross tonnage of the ship as determined in accordance with the provisions of Regulation 3.

(2) The moulded draught (d) referred to in paragraph (1) of this Regulation shall be one of the following draughts:

(a) for ships to which the International Convention on Load Lines in force applies, the draught corresponding to the Summer Load Line (other than timber load lines) assigned in accordance with that Convention;

(b) for passenger ships, the draught corresponding to the deepest subdivision load line assigned in accordance with the International Convention for the Safety of Life at Sea in force or other international agreement where applicable;

(c) for ships to which the International Convention on Load Lines does not apply but which have been assigned a load line in compliance with national requirements, the draught corresponding to the summer load line so assigned;

(d) for ships to which no load line has been assigned but the draught of which is restricted in compliance with national requirements, the maximum permitted draught;

(e) for other ships, 75 per cent of the moulded depth amidships as defined in Regulation 2(2).

Regulation 5

Change of net tonnage

(1) When the characteristics of a ship, such as V, V_c, d, N₁ or N₂ as defined in Regulations 3 and 4, are altered and where such an alteration results in an increase in its net tonnage as determined in accordance with the provisions of Regulation 4, the net tonnage of the ship corresponding to the new characteristics shall be determined and shall be applied without delay.

(2) A ship to which load lines referred to in sub-paragraphs (2)(a) and (2)(b) of Regulation 4 are concurrently assigned shall be given only one net tonnage as determined in accordance with the provisions of Regulation 4 and that tonnage shall be the tonnage applicable to the appropriate assigned load line for the trade in which the ship is engaged.

(3) When the characteristics of a ship such as V, V_c, d, N₁ or N₂ as defined in Regulations 3 and 4 are altered or when the appropriate assigned load line referred to in paragraph (2) of this Regulation is altered due to the change of the trade in which the ship is engaged, and where such an alteration results in a decrease in its net tonnage as determined in accordance with the provisions of Regulation 4, a new International Tonnage Certificate (1969) incorporating the net tonnage so determined shall not be issued until twelve months have elapsed from the date on which the current Certificate was issued; provided that this requirement shall not apply:

(a) if the ship is transferred to the flag of another State, or

(b) if the ship undergoes alterations or modifications which are deemed by the Administration to be of a major character, such as the removal of a superstructure which requires an alteration of the assigned load line, or

(c) to passenger ships which are employed in the carriage of large numbers of unberthed passengers in special trades, such, for example, as the pilgrim trade.

Regulation 6

Calculation of volumes

(1) All volumes included in the calculation of gross and net tonnages shall be measured, irrespective of the fitting of insulation or the like, to the inner side of the shell or structural boundary plating in ships constructed of metal, and to the outer surface of the shell or to the inner side of structural boundary surfaces in ships constructed of any other material.

(2) Volumes of appendages shall be included in the total volume.

(3) Volumes of spaces open to the sea may be excluded from the total volume.

Regulation 7

Measurement and calculation

(1) All measurement used in the calculation of volumes shall be taken to the nearest centimetre or one-twentieth of a foot.

(2) The volumes shall be calculated by generally accepted methods for the space concerned and with an accuracy acceptable to the Administration.

(3) The calculation shall be sufficiently detailed to permit easy checking.

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APPENDIX 1

FIGURES REFERRED TO IN REGULATION 2(5)

In the following figures:

O = excluded space.

C = enclosed space.

I = space to be considered as an enclosed space.

Hatched in parts to be included as enclosed spaces.

B = breadth of the deck in way of the opening.