Ship surveying

Ship measurement is the determination of the volume of a seagoing ship ( English tonnage of a ship ).

Tonne = barrel from Celtic (Middle Irish / Gaelic: tunna ), from there into Middle Latin (tunna = barrel), penetrated into the Germanic and Romanic vernacular around 600 AD . The term “ton” comes from Anglo-Saxon (tunne = barrel) as a unit of measurement that was used worldwide because of the British rule of the sea at the time .

History of ship surveying

Different systems

First and foremost it was the ports and the authorities responsible for shipping who needed a number, but shippers or recipients of goods were also interested in such a number. In general, they wanted to know what “loading capacity” a particular ship had, where “loading capacity” could be a measure of both volume and weight. The first traces of such an investigation can already be found in an Egyptian inscription, which proves that Nile ships were taxed by the pharaohs according to the amount of grain carried by the ships.

The Greeks classified the size of their cargo ships according to the number of amphorae that could hold the holds.

In the Middle Ages, wine was an important commodity in France, England and the Netherlands , which, due to its uniformity in weight and packaging, was well suited for determining load capacity. Since the uniform packaging was the wine barrel, i.e. the wine barrel, the term “barrel” was derived from this as a measure of space or weight for ship measurement.

In Scandinavia and on the Baltic Sea , the wine trade played a subordinate role. At the same time, the term “ load ” was used as a measure of the size or loading capacity of ships.

The wine barrel as the original unit of measurement

However, since the size and content of the wine barrels at that time differed, a decree was issued in 1422 under the English King Henry V , according to which it was forbidden to transport wine in barrels of less than 252 gallons. From then on, the weight of an English barrel corresponded to that of such a wine barrel. It was set at 2240 pounds sterling (a long ton ). This gave a binding unit of measurement that made it possible to precisely calculate the duties (taxes) for the trade in wine.

Due to the dominant position of England in maritime trade since around the 17th century, which also existed for a long time, all shipping and maritime trade states had to give up the then customary methods of measuring the size and loading capacity of seagoing vessels and follow the British procedure, so that, for international trade, the national surveying codes were the same as or very closely related to the UK surveying codes.

One of these taxes is known as the prisage . With more than 20 tons (barrel) of cargo, a barrel was due once in front of the mast and once behind the mast. If a ship could only load less than 10 barrels, no prisage was due.

In addition to the price , other taxes were levied on imported goods. These were referred to as tunnage if the fee was based on the unit of space ton , as poundage if it was a fee per unit of weight ton . The deeper reason for this was that the customs officers at the time only had to count the wine barrels that the fully loaded ship was carrying; the more one related the taxes to these values, the more one spoke of the 10 or 20 ton ship.

In the documents from that period, 13-14 Century, in which information is given about the numbers of the size of the ships, the tonnage generally appears in a rounded number (20, 40, or 100 tons).

A typical cog around the time was 240 tons, a British Nef was 180 tons.

It was not until the beginning of the 17th century that the tonnage of the ships was specified more precisely, as can be seen from lists with data on warships, and around 1630 they finally stopped rounding the tonnage down to tens or hundreds. In the lists of warships, in addition to the tonnage, there are also figures on the length, breadth and depth of the ships. The tonnage was specified using a formula with a product of keel length times width times depth divided by 100, with all length specifications being based on the British system of measurement. Including commercial vessels were determined according to this rule, like lists of ships of the British East India Company ( British East India Company is apparent). This rule for determining the tonnage was first mentioned in a treatise in 1624 by Admiral Sir William Monson (Monson rule).

Since trade was already very complex in the nature of the goods, there was often a need to get an adequate idea of ​​the  carrying capacity of  a ship. The tonnage determined according to the Monson rule mostly came very close to the carrying capacity given the way the ships were built at the time. This also applied to ships with different designs and underwater parts, because these ships were much more uniform then than is the case later and today.

In Edmund Bushnell's book (1678) The Complete Shipwright , he writes that shipbuilders in England calculated the tonnage of the ships from a product of the keel length times the ship width times half the width divided by 94 or even by 100 (Bushnell's rule of measurement). The use of half the width instead of the depth of the hold according to the Monson rule was obviously intended in order to avoid difficulties in measuring the depth of a loaded ship.

The British company " Lloyd's Register of Shipping " was founded in 1760 as the first classification society . At that time there was a "Coffee House" owned by Edward Lloyd in the City of London . This “coffee house” was the meeting point for ship owners , brokers and merchants to find out more about trade, shipping and their operators. This was the nucleus of today's oldest classification society. Bit by bit, some shipowners and shipyard owners joined together in a company with the aim of improving understanding and the exchange of information between the two parties “manufacturer” and “buyer”. In addition, it was very important to the shipowners to create an institution that was professionally capable of evaluating ships so that insurance could be concluded for the ships on this basis .

Bushnell's Builder's Old Measurement Rule had had a very negative impact on safety in shipbuilding. When trying to build the largest possible ships with the smallest possible tonnage, the ships had to be narrower when using a formula in which the measure of width appeared as a square. The consequences of this were that many ships became unstable for reasons of measurement. In 1821, therefore, a commission was set up to review the surveying regulations. The latter suggested measuring the hull between the empty waterline and the low-loading line, but was of the opinion that such a method would involve considerable practical difficulties, so that it was better to measure the ships "inside". For this purpose, the following was proposed in detail:

The width should be measured in five places and the depth in two places. The product of the mean width and mean depth multiplied by the length and divided by 112 should be the numerical value for the tonnage. The number 112 was chosen in order to obtain the same tonnage figures as possible as they would have resulted from the old regulation. However, the proposal was not recognized.

Moorsom system

George Moorsom, the secretary of a committee convened by the British Admiralty in 1847, proposed a system according to which the total volume of a ship (gross register tonnage / gross register tonnage ) as well as the volume used for the transport of cargo or passengers (net Register-Tonnage / Net Register Tonnage ) should be determined and registered in the ship's documents. This system has been in the British Merchant Shipping Act of 1854 ( Merchant Shipping Act introduced authentic).

According to Moorsom's suggestion, the volume of a ship should be measured as accurately as possible on the inside and calculated in cubic feet. The tonnage is calculated from this result by dividing it by 100. The number 100 as a divisor was chosen in order to have as close a number as possible, which should be as close as possible to the previous regulations.

It was therefore: 1 GRT = 100 cubic feet = 2.83 m³.

This survey envisaged that the entire volume of a ship below the upper deck was measured, the rooms above the upper deck, which were used, for example, to accommodate passengers, store cargo or supplies, were measured if they were closed rooms . The sum of the volume resulted in the gross tonnage, from which the register or net tonnage was determined by deducting certain volume. Rooms for the crew were exempt from being included in the gross room salary, provided that they were above the survey deck and totaled less than five percent of the gross tonnage.

The net space is the gross space minus the spaces for the crew, supplies, water ballast, etc. The following applies to the engine rooms: If the space occupied by the engine or boiler is more than 13% of the gross space , then 32% of the gross space is considered Engine room deducted; it is assumed here that the surplus is taken from the coal bunker .

The Moorsom system was adopted more or less unchanged by other states in the following years. In 1873 it was applied in Germany, Austria-Hungary, Denmark, USA, France, Italy, Norway and the Ottoman Empire, while Belgium, Spain, the Netherlands and Sweden intended to introduce it.

In 1954, Moorsom's rule celebrated a hundredth anniversary. During this time, a lot had happened in ship technology , fuel consumption for ship machines fell from 2.5 kg to 0.27 kg for turbine systems and even to 0.17 kg for engine systems. The fuel compartments shrank, but the measurement formula remained. The Moorsom system was a good trick to equip ships of the same type or sister ships with different numbers.

See also: Simpson's rule

Examples

The parties (maritime naval forces ) - here red and blue - report on their mock attack on a ship:

Blue: Our non-stop attacking submarines sank a freighter of 13,000 tons from a heavily secured enemy convoy in the North Atlantic .

Red: A pack of enemy underwater forces attacked one of our convoys in the western part of the North Atlantic. Six enemy submarines were sunk by the security forces. One of our smaller freighters weighing 5,500 tons was lost.

The two did not misrepresent the size of the ship, although the difference in the dimensions of the booty is 7,500 tons. Here we read for the first time by omitting the term dimension that one can be deceived about the size of ships.

To judge a ship and its technical performance, one really only needs to know its space and its carrying capacity . You can load the ship with cotton balls without using its carrying capacity, or with railroad tracks without using its space to the full.

Fatherland

When measuring the gross room as with the net room number, magic can be done. A famous example of this is the fatherland , which was handed over to the USA after the First World War and then continued under the name Leviathan . The German measurement certificate gave a GRT of 54,282 for the ship . The sister ships , the Imperator and the Bismarck , were measured with 52,226 GRT and 56,621 GRT. The Bismarck , later called the Majestic , was initially the largest ship in the world merchant fleet .

Since people and the Americans think a lot of records, the Leviathan was re-measured. After the re-measurement, she then had 59,957 GRT overnight and the Americans had the largest ship in the world merchant fleet. During the Great Depression , this record was expensive and the vessel was measured again - now it had overnight only 49,942 tons. The ship was not lengthened or shrunk, but open superstructures were made closed and vice versa.

Tons of salad

To illustrate the tons of salad.

A look at the ship's papers: there we have a ship's measurement certificate . From this we can see that the ship has an enclosed space of 21342 m³. His deserving room dimension - that is the net room -  has a circumference of 15232 m³.

Converted to British dimensions , the following figures result:

• Gross space 7541 register tons,
• Net space 5382 register tons.

The next measurement certificate is the Suez measurement certificate (Suez Canal Special Tonnage Certificate).

• Gross space 7645 register tons and that of the
• Net space is 5742 register tons.

With regard to the differentiation of the net tonnage, there are still no major concerns, since the channel fees for the Suez Canal depend on the net room. Strangely enough, the sanitary facilities are also included in the “earning” room. What is noticeable is the gross register ton , it is different. Our ship was not measured for the sailing area of the Panama Canal , otherwise the numbers would be even more different. We continue to look at the ship's documents and come across the ship's safety certificate . There we read: The ship is only allowed to load 8,900 tons of cargo ; and we see that according to the documents issued by the shipyard , our ship fully loaded displaces 13509 tons of water , which means that the ship and cargo weigh 13509 tons . The numbers summarized again:

• 13509 tons of water displacement
• 8900 tons load capacity
• 7541 register tons of gross space
• 5382 register tons of net space
• 7645 register tons gross area Suez
• 5742 register tons net area Suez

Tonnage: a measure of volume and carrying capacity

Loading mark

In lists, tables and statistics on ocean-going vessels, in addition to the gross tonnage (GRT in English gross tonnage (GT)), the deadweight calculated by the shipyard in tons deadweight (tdw), a deadweight tonnage or approval tonnage is also given. If you compare the relationship between the two numbers, you can see that the value spreads quite widely and varies from ship types to different ship sizes. They can also be very different for ships of the same size and purpose, even for sister ships. The reason for the differences in size and scatter lies in the type of the two numerical values ​​compared here. While the gross tonnage determined by the measurement is a measure of the volume and volume of the ship, the carrying capacity indicates the maximum amount of payload a ship can take. This number can be given in short tons, long tons or in metric tons of 1000 kg. The carrying capacity is calculated as the difference between displacement (weight of the displaced water up to the maximum permissible draft) and the dead weight of the fully equipped ship (displaced water up to the empty draft).

A note of the load capacity is attached to the outer skin in the middle of the ship, the so-called Plimsoll mark (loading mark ) , which is visible to everyone . The German introduction of the loading brand (low-loading brand) is a merit of the last German emperor , he caused the German shipowners to set a good example.

• See also: Samuel Plimsoll

1st International Ship Surveying Convention (Oslo Convention 1947)

Updates (changes, additions, e.g. shipbuilding adjustments)

A distinction was gross tons , short BRT (Engl. GRT Gross Registered Tons ) of net registered tons or NRT (Engl. Net Registered Tons ).

BRT covered the whole ship, so

• between surveying and upper deck,
• below the measurement deck (lower deck space content),
• Content of hatches above deck,
• Content of the superstructures.

NRT are calculated from BRT through deductions, namely the

• Crew accommodation,
• Command bridge,
• Machine and boiler rooms,
• Fuel bunker,
• Water ballast tanks,
• Pump rooms,
• Provision rooms,
• Workshops and storerooms.

Terms from the Oslo survey

Survey deck

The upper deck on ships with no more than one full deck, and the full next deck below the upper deck on ships with two or more full decks.

Open deck

A ship with the surveying benefits like a protective decker, but without survey openings and marked on the outside with a survey mark indicating the maximum permissible draft.

Full-decker

A ship whose freeboard is set off from the upper deck, which is also the survey deck. All rooms below this deck above the double floor are included in the measurement calculation.

Protective decker

A ship that has a complete upper deck (protective deck) above the survey deck , which is also the freeboard deck, which has been made open by survey openings with prescribed dimensions, as are the bulkheads below . It is also called a shelter decker.

Exchange ship

A ship that was measured as a protective and full-decker and could switch between the two measurement results according to the respective set freeboard.

present

2. International Ship Surveying Convention (London 1969)

Ribs and waterline crack

International Maritime Organization (IMO UN specialized agency) in connection with the International Ship Surveying Convention of 1969 , generally London 69 

On July 18, 1982, the International Ship Surveying Convention of June 23, 1969 ( London 69 for short ) came into force, which after a transitional period of twelve years in 1994 replaced all previous national surveying regulations. To date, 132 countries have signed the London Agreement, which corresponds to around 98% of world tonnage. The Federal Republic of Germany became the 21st country to join the Convention on January 22, 1975 (Federal Law Gazette II / 75).

Gross registered tonnage (GRT) and net registered tonnage (NRT) have been replaced by the dimensionless numbers gross tonnage (GT) and net tonnage (NRT ) .

According to the GT or NRZ, the tonnage dues , the fees for port use, canal or lock passage and pilotage are still calculated .

The exact calculation of GT and NRZ is based on the following formulas:

${\displaystyle BRZ=K_{1}\cdot V}$

${\displaystyle NRZ=K_{2}\cdot V_{c}\left({\frac {4T}{3H}}\right)^{2}+K_{3}\left(N_{1}+{\frac {N_{2}}{10}}\right)}$

Here, boundary conditions must be observed:

${\displaystyle \left({\frac {4T}{3H}}\right)^{2}}$ must not be greater than one,

${\displaystyle K_{2}\cdot V_{c}\left({\frac {4T}{3H}}\right)^{2}}$ not less than 0.25 GT and

${\displaystyle NRZ}$ not be less than 0.30 GT.

In the formulas:

${\displaystyle V=}$ Numerical value of the content of all closed spaces (in cubic meters)

${\displaystyle V_{c}=}$ Numerical value of the contents of all holds (in cubic meters)

${\displaystyle K_{1}=0{,}2+0{,}02\cdot \log _{10}V}$

${\displaystyle K_{2}=0{,}2+0{,}02\cdot \log _{10}V_{c}}$

${\displaystyle K_{3}=1{,}25{\frac {BRZ+10000}{10000}}}$

${\displaystyle T=}$ Draft amidships (in meters)

${\displaystyle H=}$ Side height amidships (in meters)

${\displaystyle N_{1}=}$ Number of passengers in cabins with a maximum of 8 beds

${\displaystyle N_{2}=}$ Number of otherwise permitted passengers

${\displaystyle N_{1}+N_{2}=}$ Total number of permitted passengers (disregarded if fewer than 13)

These values are in the official International Tonnage Certificate ( International Tonnage Certificate recorded). No international ship's measurement certificate is required for yachts less than 24 m in length .

Suez Canal Special Tonnage Certificate

The fees for the journey through the Suez Canal are calculated based on the Suez Canal Special Net Tonnage - SCNT . For the calculation of this tonnage special rules apply, which were originally laid down according to the English Moorsom system by an international commission in Constantinople in 1873 . The background was a dispute between the Suez Canal Company and, in particular, British shipowners over the tonnage to be used as a basis for the canal fees. Since the compromise found by the commission contained minor deviations from the Moorsom system and the Suez Canal Society was obliged to charge the ships of all nations with the same fees, but mistrusted the register tons specified in the ship's documents, it reserved its own measurement of the ships . This led to the Suez Canal Special Tonnage Certificate. As a result of changes in shipbuilding , the rules were amended in 1904. In 1939, additions were made to the uniform treatment of the machine system and auxiliary boiler (Donkey boiler). In 1955 the set of rules was published as a summary, the complete work was called Règles de la Jauge de Suez of the Compagnie Universelle du Canal Maritime de Suez with the rules of 1873 and 1904 as well as additions. In principle, these rules still apply today, but have been adapted to the development of shipbuilding (tankers, LNG , container ships). They can be found today in Articles 93 to 98 of the Rules of Navigation of the Suez Canal Authority . The Suez Canal Net Tonnage - SCNT resulting from these rules is confirmed in the Suez Canal Special Tonnage Certificate , which is issued by the classification societies or the authorities of the flag states and recognized by the Suez Canal Authority. This certificate must be present every time you cross the canal. If this is not the case, it can theoretically also be issued by the Suez Canal Authority, which leads to corresponding delays.

In view of the considerable amounts of cargo in containers on deck, these are also taken into account when calculating the charges.

See also: Constantinople Convention of the Suez Canal, Suez Canal

Panama Canal Universal Measurement System - PC / UMS

The Panama Canal Commission (PCC) joined the International Convention London 69 in October 1994 . The starting value for the Panama Canal Universal Measurement System - called PC / UMS , is the gross volume (in m³) according to the London rules. The net tonnage, which is more important for the canal fees, was not taken over after the London 69 . The application of the PC / UMS Net Tonnage is described in the rules Proposed changes in rules for measurement of vessels for the Panama Canal - April 1994 . Since 1997, the total of the deck containers has also been recorded as volume in the net tonnage, here the standard containers (20 feet (0.3041 cm) × 8 × 8 = 1 TEU) are taken. With different container stowage variants, the one that gives the highest volume value is always selected, e.g. B.

• 100 containers times 20 × 8 × 8.5 = 3851.6 m³
• 50 containers times 40 × 8 × 9.5 = 4304.7 m³

and this is then calculated back to the standard container to the unit TEU.

See also: Panama Canal

Use of ship surveying

Register bins or room numbers are the basis for many regulations relating to the ship

• Calculation of fees (harbor fees , pilotage fees ), duties ( taxes ), fees (canal passages e.g. Suez Canal, Panama Canal , Kiel Canal )
• The classification of the ship in legal regulations (national and international)
• Ship safety ( SOLAS ), ship manning, ship manning training regulations ( STCW ), prevention of marine pollution from ships ( MARPOL )
• The registration of the ship ( ship register )
• Statistics in shipping and shipbuilding

History of the German ship surveying system

Until the founding of the empire in 1871, the measurement of seagoing vessels was solely a matter for the coastal states and ports. In 1819 , Hamburg had set an instruction to the harbor master for the measurement of seagoing ships. The measurement in Hamburg feet is 286 millimeters.

The length of the ship over the deck between the two stems, the greatest width of the space between the main planks and the depth of the space between the planks on the keel and the deck planks. A dimension with a so-called room length is determined by subtracting the room length from the length above deck. Multiply this room length by the greatest width and room depth and convert the result by dividing it with a divisor, which could be between 280 and 320 depending on the type of ship as a characteristic of the ship shape, converted into Hamburg loads of 6000 pounds .

The procedure was different on the Baltic coast . There three widths were measured, one in the middle and two each 1/12 of the length of the ship. The mean value obtained from the latter two was subtracted from the latitude amidships. From the reduced width dimension, a box was determined by multiplying the length and depth of the depth of the room, which divided by a divisor represented the result and resulted in the measure for the load-bearing capacity in loads of 4000 pounds .

Old load descriptions

• 1 load = 17 barrels (or kantjes ) = 1666 kg pegs
• 1 kantje = 74 kg pegs
• 1 basket = approx. 1 quintals = approx. 50 kg
• 1 barrel = (e.g. anchovies and sardines ) = 30 lb. = 13.608 kg
• 1 warp = 4 pieces
• 1 long hundred = 33 warps = 132 pieces
• 1 thousand = 10 long hundred = 1320 pieces
• 1 load = 10 thousands = 13200 pieces
• 1 crade = 500 herrings = 1000 sprats
• 1 mease = 600 pegs
• 1 cran = 37 ½ gallons = 170 liters of herrings

It is also an insurance term : when the burden goes on the insurer.

Then there is also a shipbuilding - like the nautical expression there, a storage space is also referred to as a load (e.g. the lowest room in the ship into which you can still drive a load, there is also the name for food rooms, e.g. Bread load, meat load, etc.).

See also

• Explanations of some of the technical terms used here
• Tonnage profit determination
• Archimedean principle
• Surveying (regatta sailing)

swell

• IMO resolutions and interpretations
• On the International Ship Surveying Convention, London 1969
• A.492 (XII) of November 19, 1981 Entry into force of the International Ship Surveying Convention of 1969
• A.493 (XII) of November 19, 1981 Definitions: Ton Gross Tonnage = Gross Tonnage
• A.494 (XII) of November 19, 1981 Interim solution for tonnage measurement
• A.540 (13) of November 17, 1983, tonnage measurement of certain ships for the purposes of the International Convention on Standardization for the Training, Certification and Watchkeeping of Seafarers of 1978
• A.541 (13) of November 17, 1983 Interim solution for the tonnage measurement of certain ships with a view to the 1973 International Convention for the Prevention of Pollution from Ships, adopted on November 17, 1983
• A600 (15) dated November 19, 1987 IMO identification number for ships
• A758 (18) dated November 4, 1993 Uniform entry of notes on the old BRT measurement results

literature

• A. van Driel: Tonnage Measurement, Historical and Critical Essy . The Hague, 1925
• Yrjö Kaukiainen: Tons and Tonnages. Ship Measurement and Shipping Statistics, ca.1870–1980 . In: International Journal of Maritime History Vol. 7, 1995, pp. 29-56.
• Karl Joachim Klüver: History of ship measurement . In: HANSA - International Maritime Journal , Issue 1/2009, pp. 32–37, Schiffahrts-Verlag "Hansa" C. Schroedter & Co., Hamburg 2009, ISSN  0017-7504

Web links

Wikisource: Ship surveying  - sources and full texts

Commons : Ships of each period  - collection of images, videos and audio files

• International Ship Surveying Convention of 1969 ; incl. calculation of gross tonnage (GT), Switzerland, 2005 ( PDF )
• The gross tonnage as a new unit of ship measurement PDF (393 kB)
• Tariff regulations for the port pilot area - Hamburg
• See-Berufsgenossenschaft website
• Surveying method

Individual evidence

1. ↑ ton . In: F. Kluge: Etymological Dictionary of the German Language , 1967, page 782
2. ↑ Excerpt from the Merchant Shipping Act digitized on archive.org (English)
3. ↑ Tabular overview of the tonnage systems of other countries Digitized at archive.org (English)
4. ^ Final report of the Commission of Constantinople of December 18, 1873 Digital copy on archive.org, in French
5. ↑ IMO ( Memento of the original from February 28, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Official Homepage (English) 
6. ^ Final report of the Commission of Constantinople of December 18, 1873 Digital copy on archive.org, in French
7. ↑ suezcanal.gov.eg
8. ↑ Constantinople Convention of the Suez Canal on Wikisource (English)
9. ↑ Official site of the Panama Canal
10. ↑ IMO website about SOLAS (English)
11. ↑ BSH website about Solas (German-language summary) ( Memento of the original from March 5, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. 
12. ↑ IMO website about the STCW ( Memento of the original dated July 3, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. 
13. ↑ Data on the MARPOL Convention ( Memento of the original of April 30, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. 
14. ^ Walter Kresse: Ship surveying before 1870 . In: Journal of the Association for Hamburg History , Volume 58