We measure lengths, areas, volumes, weights to define things. Measures when combined with Time show the changes that occur in things. We measure events or happenings, for their start, the rate at which these actualize, duration and termination. Measures are very important in recording and recreating events and happenings.
Measurement is finding size or amount of some quantity, and expressing it as a number of defined units. All measurements are based on comparisons. A thing to be measured is compared with something similar, or with a thing that has already been calibrated -measured against a known reference.
There was a time, when things were measured in terms of body sizes and body’s capacities. Long Distances were measured for the travel time required, like in lunch breaks or night halts. Short distances or Lengths were measured in arm lengths or foot steps. Smaller sizes were measured with the palm, length of a finger or width of a thumb. Finer widths were measured in terms barley grain. Volumes were measured as the holding capacity of limbs like pinch or palm. Weights were measured in terms of carrying or displacement capacity of a person or animal, such as head load, cart loads, horsepower.
Measures based on body sizes or capacities had many racial and regional variations. It was possible to equate out such differences in a barter trade between neighbours. But the same was proving to be very difficult for trade with far-off regions. There was an acute need for some common measure system. Gradually trading blocks concurred to a common tradition of Nominal measurements. Conversion of measures with adjoining trade regions was facilitated by intermediaries like brokers, caravan masters and shippers. The inconsistencies of the measure conversions were partly solved when monetary pricing replaced the bartered trading.
Over a period of time many units for measuring length came into practice in different societies. Lengths were measured in Angula, Danda, Goruta or Korsa, Dhanush, Inches, Cubit, Digit, Thumb, Hand, Arm, Feet, Yojan or Jojan, Yard, Chain, Link, Fathom, Rod, Furlong, Miles, Nautical miles, League, Stadia. Early metric system had several units @ 10X such as Millimetre, Centimetre, Decimeter, Metre, Dekametre, Hectometre, Kilometre. To these were added micro measures like nanometre, micron and Angstrom.
Roman pes or foot was divided in 12 parts called unciae, from which the words inch and ounce have derived. Similarly yard (gird) can be traced back to early Saxon kings who wore a sash or girdle around the waist which was removed and used to measure lengths. Later King Henry decreed that a yard should be the distance from the tip of his nose to the end of his outstretched thumb.
During the French Revolution (1870) the National Assembly of France asked French Academy of Sciences to formulate a scientific and rational measure system. Such a system was expected to be: 1 Neutral and Universal, 2 Replicable anytime and anywhere, 3 to have Decimal Multiples, 4 to follow Common Prefixes and 5 be Practical and Simple to use. The rationale for such a system forced many countries of Europe to think on similar strategies.
Industrial Revolution period saw faster means of transport and better communication systems. It fostered trade between far off regions and different political domains. The producer and the consumer were very distanced. British, Spanish, French and Dutch empires through trading outposts and colonies controlled major part of the international trade. These Trading Blocks maintained their own measurement system. In spite of trading blocks, the need for a common, logical, definable, replicable and comparable system of measurements was acutely felt.
Foot & Pound system was widely used in British colonies and their trading outposts besides USA and parts of Canada. Foot & Pound system was a well developed but not very coherent as relationships between measures were illogical. Metric System on the other was mathematical but had too many sub fractions. Different nations, regions, and trade groups favoured different sub fractions, creating confusion. This was perhaps the major deterrent for other countries (chiefly those following the FP system), desiring a change over to the Metric System. Historically Metric system has seen many versions: CGS or the Centimetre-gram-second system, MKS or the Metre-kilogram-second system, MTS or the Metre-tonne-second system.
First International effort to develop a worldwide policy for weights and measures was made during May 1875. Some 17 countries signed a Metre Convention or Convention du Mètre, an international treaty to create a ‘permanent mechanism to recommend and adopt further refinements in the metric system’. This was directed towards defining what constitutes a standard measure unit and means to replicate it in great accuracy anywhere and anytime and towards defining sub units for the main measures.
The metric convention was held at the time of heightened Industrial activity during the Industrial Revolution period across Europe and USA. Signatories of Treaty of Metric were: USA, Germany, Hungary, Belgium, Brazil, Argentina, Denmark, Spain, France, Italy, Peru, Portugal, Russia, Sweden, Norway, Switzerland, Turkey, Venezuela.
After the Convention du Mètre in France in 1875 a General Conference on weights and measures or Confèence gènvrale des poids et mesures CGPM was organised in 1889. Eight CGPM, at rough intervals of 4 years, were held till 1933, followed by an inactive period due to world war II. These meetings gradually evolved a worldwide policy on the advice of scientists and metrologists.
Conférence générale des poids et mesures (CGPM), an intergovernmental conference of official delegates of member nations and the supreme authority for all actions. It continued the deliberations of Convention du Mètre.
Comité international des poids et mesures (CIPM), consisting of selected scientists and metrologists, which prepares and executes the decisions of the CGPM and is responsible for the supervision of the International Bureau of Weights and Measures.
Bureau international des poids et mesures (BIPM), a permanent laboratory and world centre of scientific metrology, the activities of which include the establishment of the basic standards and scales of the principal physical quantities and maintenance of the international prototype standards.
Hectic reconstruction activities began everywhere in the post world war II (1945) period. Major impediments to this effort were the differing National Standards. To allow free flow of raw materials, equipments and technology a platform of common Standards and Specifications was required. In 1946, delegates from 25 countries met in London to create a new organization, to facilitate the international coordination and unification of industrial standards. The new organization, Organisation internationale de normalisation, ISO, officially began operations on 23 February 1947, in Geneva, Switzerland.
The word ISO was selected to represent the organization in all languages because it is derived from the Greek isos, meaning equal.
9th CGPM in 1948, meeting after 15 years gap due to WW II formally adopted a recommendation for writing and printing of measure unit symbols and numbers. The name Systeme International d'Unites (International System of Units), with the international abbreviation SI, was adopted for this New Metric System.
In 1960, the CGPM revised and simplified the measure system. Seven Base Units such as: meter (Length), kilogram (Mass), second (Time), ampere (Electric current), kelvin (Temperature), mole (Substance), and candela (Luminous intensity), were established.
Acceptance of SI has been varied. For French and other European countries including their colonies, already using MKS system, adopting the new system (SI) was very easy. In 1965 Britain started using it. Canada, Australia, New Zealand, and South Africa quickly followed and soon exceeded the speed of change in Britain. In 1975, USA officially accepted the Metric system (in the form of SI system), but no specific schedule was set for the change over.
SI MEASUREMENTS: As a designer, we are concerned with formulating or creating new entities, and also using ready parts and components. For both the purposes, we need to specify the Measures. ISO has formulated rules for Writing and Specifying Measures in drawings, documents, specifications and other forms of communication. This is done to avoid any ambiguities in interpretation of information.
WRITING AND SPECIFYING MEASURES:
▪ All decimal numbers must be preceded by a zero if no other digit exists. e.g. 0.121 (and not as .121 )
▪ No thousand or hundred markers are to be used, e.g. 1000 (and not 1,000), but where large number of digits are involved a blank or space (equal to 1 digit or not less than ½ digit in width) may be used as a separator, in place of a marker. However, where only four digits are used no space as a separator need be provided. e.g. 100 000, 10 000 or 1000 (but not 1 00 000 or 1 000)
▪ For length units km / m / mm, all must be in small letters (Unit indicators may be used, only when necessary. e.g. architectural plans have nearly all measures in mm, so the mention of mm should be avoided. However, in the same drawing if weight or volume or such other measures are to be indicated then unit identifiers for such units may be indicated).
▪ Full names of units even when these are named after a person, are written in small letters: ampere, volt etc., with the exception W for watt and J for joule.
▪ For liquid measure however lt may be written as Lt (to differentiate between 1 and l ).
▪ Plurals need not be used. (kms, mts, kgs).
▪ Point or Full stop for abbreviation may not be used, for example as in m.m. or mm.
▪ Where cubic or square measures are to be shown: 3m3 = will mean three cubic metres and not 33 i.e. 3 x 3 x 3 = 27cmt.
▪ Following common units are acceptable
Length mm m km (all 1000 factored)
Weight gm kg mt or t (all 1000 factored)
Liquid mlt Lt klt (all 1000 factored).
▪ Where traditionally only one unit is accepted, and if there are no chances of ambiguity, the measure nomenclature (mm, km, gm etc.) may not be mentioned. (E.g. cloth width = 1.200). If in one sheet of drawing (or a document) only one scale and one mode of measure are used, the nomenclature may be mentioned as a general instruction for the drawing.
▪Where drawings or details are likely to be reduced or enlarged in processing / copying, a graphical scale preferably showing 100 mm bar may be shown. If 100 mm size is not suitable due to micro reduction or macro enlargement, suitable multiples of 100 mm for upwards scaling and 10x fractions of 100 mm for downwards scaling maybe used.
MEASUREMENTS ON DRAWINGS
When both mt & mm are used on drawings, it will be less confusing if the dimension is always written to three places of decimals, i.e. 3.450. No unit symbol need be shown unless a lesser number of decimal places are used; i.e. 3.450 or 3.45 m and under some circumstances 3.5 m, are all correct. Of the options, 3450 and 3.450 both are preferred. Where no ambiguity can arise, symbols may be discarded, according to following rules:
▪ Whole numbers indicate mm
▪ Decimated fractions to three palaces of decimals indicate m (and also by implication, mm)
▪ All other dimensions must be followed by the unit symbol.
▪ Where dimensions refer to different types of measures (lengths, weights, temperature etc.), preferably all units should be indicated or all units other than the major one should be indicated.
▪ Main dimensions and the tolerance (fitments, limits, margins etc.) etc. should be in the same unit system.
▪ Where main dimensions are accompanied by + or - range, both should be in the same unit.
From Interior Design Notes : Interior Design Practice & Office Management - II