トン数

Tonnage — Grokipedia Fact-checked by Grok 3 months ago Tonnage Ara Eve Leo Sal 1x Tonnage is a measure of the internal volume of a ship or the weight of materials, most commonly applied in maritime contexts to assess a ship's capacity for regulatory, commercial, and safety purposes, and in mining to quantify the total mass of ore or mineral resources extracted or estimated in a deposit. [1] [2] In mining, tonnage typically refers to mass in metric tonnes (1,000 kg) or short tons (907 kg), depending on regional standards. [2] In shipping, tonnage originated from medieval taxation on wine casks (tuns) transported by sea and evolved into standardized metrics under the International Convention on Tonnage Measurement of Ships, 1969, administered by the International Maritime Organization (IMO). [1] The convention, adopted on June 23, 1969, and entering into force on July 18, 1982, establishes a uniform system to replace disparate national methods, applying to ships of 24 meters or more in length engaged in international voyages, with ships built on or after July 18, 1982, required to comply immediately and existing ships by 1994. [1] [3] It defines gross tonnage (GT) as a measure of the total internal volume of all enclosed spaces on a ship, calculated using the formula GT = K₁ × V, where V is the total volume in cubic meters and K₁ is a coefficient (0.2 + 0.02 × log₁₀V), providing a nonlinear, dimensionless index of overall size independent of a ship's design or purpose. [1] Net tonnage (NT) , in contrast, measures the useful cargo-carrying capacity by deducting non-earning spaces (such as crew quarters and machinery areas) from gross tonnage, using a formula that incorporates cargo volume, engine room deductions, and adjustments for passenger ships. [1] These metrics, historically linked to a register ton of 100 cubic feet (2.83 cubic meters) of volume in older systems but now derived from a standardized volumetric formula, influence port fees, canal tolls, safety regulations, and insurance rates, with 167 contracting states (as of 2025) covering approximately 99% of global gross tonnage adhering to the convention. [1] [4] Beyond maritime use, tonnage denotes the total weight of materials in industries like mining , where grade-tonnage models statistically relate the average mineral concentration (grade) to the deposit's total mass (tonnage) to evaluate economic viability and resource potential. [2] In mineral deposit assessments by the U.S. Geological Survey (USGS), tonnage represents the pre-mining in-place resource estimate in metric tons, often plotted logarithmically against grade to model deposit types such as porphyry copper or epithermal gold veins, aiding exploration and reserve estimation. [5] [6] For example, low-grade bulk tonnage deposits may involve millions of tons at concentrations below 1%, while high-grade vein deposits yield smaller tonnages at elevated grades. [2] In mining leases, tonnage rent functions as a royalty based on the tons of minerals extracted, providing a direct economic measure of production output. [7] Historically, tonnage measurements in shipping trace back to 1854 with the British Moorsom System, which influenced global standards but varied by nation (e.g., Norwegian rules for tankers) until the 1969 convention harmonized them, phasing out obsolete gross register tonnage (GRT) and net register tonnage (NRT) for new vessels while allowing legacy ships a transition period until 1994. [1] In mining, tonnage concepts underpin quantitative resource modeling developed since the mid-20th century by agencies like the USGS to predict deposit distributions and inform policy, with no significant correlation between tonnage and grade observed in certain deposit types like porphyry coppers. [6] Today, tonnage remains essential for international trade , environmental compliance (e.g., under MARPOL conventions), and sustainable resource management , reflecting its role as a foundational metric across transportation and extraction sectors. [1] [2] Fundamentals of Tonnage Definition and Units Tonnage in the maritime context is a measure of the internal volume or capacity of a ship, quantifying the total enclosed space available within its hull rather than its weight or displacement. Unlike displacement tonnage, which represents the weight of water displaced by the vessel and thus its actual mass , tonnage focuses on cubic capacity to assess overall size for regulatory, commercial, and safety purposes. [3] [8] The basic unit of tonnage, known as the register ton, historically equated to 100 cubic feet (approximately 2.83 cubic meters) of internal volume, a standard established in the mid- 19th century to replace earlier inconsistent methods. This unit originated from medieval practices where a "tun" referred to a large cask or barrel of wine, with ship capacity initially estimated by the number of such casks it could carry, blending weight and volume concepts. By the 19th century , systems evolved into purely volumetric measurements, such as the Moorsom system adopted in 1854 , which formalized the 100-cubic-foot register ton for gross calculations across enclosed spaces. [9] [10] [11] Under modern international standards, tonnage is no longer tied to a specific volumetric unit but is treated as a dimensionless index, expressed in "tons" for convenience. The International Convention on Tonnage Measurement of Ships, adopted by the International Maritime Organization (IMO) in 1969 and entering into force on July 18, 1982, established a universal framework for calculating gross and net tonnage based on the moulded volume of all enclosed spaces, applying to ships of 24 meters or more on international voyages. This convention replaced disparate national systems, ensuring consistent global application while maintaining the traditional "ton" nomenclature despite its unitless nature. [3] [12] Purpose of Measurement The measurement of tonnage originated as a means to assess a ship's cargo capacity for taxation purposes, particularly in medieval England where port dues were levied based on the number of wine casks (tuns) a vessel could carry. In 1303, King Edward I introduced the first such tax on imports and ships, calculating charges according to the ship's burthen in tuns, which served as a proxy for potential revenue from goods transported. This system extended to general harbor dues, ensuring that fees reflected the economic benefit derived from a vessel's use of port facilities. [13] [14] [15] By the mid-19th century, evolving ship designs highlighted the limitations of weight-based assessments, prompting a shift toward volume measurements for greater equity. The British Merchant Shipping Act of 1854 established a new tonnage formula based on the internal cubic capacity of the hull, aiming to eliminate biases that disadvantaged ships with deeper holds or improved cargo efficiency under prior weight-oriented rules. This reform promoted fairness in fee structures, preventing undue penalties on innovative or more capable vessels. [10] In modern contexts, tonnage measurement provides a standardized metric under the International Maritime Organization (IMO) for facilitating global trade and regulatory compliance. Gross tonnage informs requirements for safety equipment, crew manning levels, and vessel registration, while both gross and net tonnages determine port and lock fees worldwide. This uniform approach ensures equitable treatment across nationalities and designs, with tonnage-based charges avoiding distortions that could discourage advancements in ship efficiency, such as optimized hull forms that maximize capacity without proportional increases in displacement. [3] Basic Calculation Methods Tonnage calculations fundamentally rely on measuring the enclosed volume of a ship's hull, superstructures, and protected spaces. Under the modern IMO Convention, the total moulded volume V is determined in cubic meters, bounded by the shell plating or structural boundaries and excluding volumes under open decks or spaces accessible to the sea without permanent closures. Measurements are taken to the nearest centimeter or 1/20th of a foot for precision, ensuring the total volume reflects the ship's overall size for regulatory purposes. Historically, this volume was expressed in register tons of 100 cubic feet (2.83 cubic meters), but modern gross and net tonnages are dimensionless indices derived directly from V using specified formulas, without such volumetric conversion. [16] [17] [18] [3] Geometric principles form the core of volume determination, approximating hull shapes as fundamental forms like prisms, cylinders, or frustums. For prismatic sections, such as barge hulls, the volume is estimated as length multiplied by breadth multiplied by depth, adjusted by a shape factor (e.g., 0.84 for near-rectangular forms) to account for deviations from ideal geometry . Cylindrical components, common in rounded bilges or superstructures, use the formula $ V = \pi r^2 h $, where $ r $ is the radius and $ h $ the length. For irregular shapes, numerical integration techniques like Simpson's first rule divide the space into even intervals and sum weighted ordinates: V = h 3 ( y 0 + 4 y 1 + 2 y 2 + 4 y 3 + ⋯ + 2 y n − 2 + 4 y n − 1 + y n ) V = \frac{h}{3} (y_0 + 4y_1 + 2y_2 + 4y_3 + \cdots + 2y_{n-2} + 4y_{n-1} + y_n) V = 3 h ​ ( y 0 ​ + 4 y 1 ​ + 2 y 2 ​ + 4 y 3 ​ + ⋯ + 2 y n − 2 ​ + 4 y n − 1 ​ + y n ​ ) where $ h $ is the interval spacing and $ y_i $ the cross-sectional areas or breadths at each station; the trapezoidal rule serves as an alternative for simpler approximations. These methods ensure accurate volumetric assessment without exhaustive physical disassembly. [16] [17] [18] Modern surveys employ advanced tools including 3D laser scanners to generate point cloud data of internal compartments, processed by software like NaviSuite or Trimble systems for automated volume computation, minimizing errors and ena