.1 Metric and imperial conversions This item is one of the eighteen available on the Applied Environmetrics Hydrological Tables. The hydrological tables are the third in the computer- based series of tables produced by Applied Environmetrics. All of the other items in the series accept the entry of variables in a variety of metric and imperial units, but only present the results in SI units. This procedure will suit scientists, but it can be inconvenient to practitioners - especially those in the United States - who do not normally use the SI system. This item is to assist in the conversion of units of most of the output tabulations from the hydrological tables. There are three systems of units in common use. These are the US system (many units of which are the same as the old British Imperial system), the metric system and the SI system. This item is to assist in converting between these three systems.This item recognises units in either of the above three systems, and in many cases will recognize mixtures of the three. Altogether 2380 units are recognised. Conversion takes place to more standard units. Altogether to 174 units. .2 The item begins by presenting a Table of Contents from which you choose the variable of interest. The fourteen choices are: temperature, pressure, length, area, volume, speed, flow (i.e. discharge) mass, mass transport, density, energy, power, energy flux (i.e. irradiance), and specific heat capacity. The Table of Contents also lists a selection of the units that are available for conversion. Consult this documentation for a complete list and for advice on acceptable entries. Remember that the table exists for conversion between presently used systems of units. Because imperial fluid measures are no longer used the gallon, quart and fluid ounce all refer to US measures. Similarly, the ton as a unit of mass refers to the short (2000 avoirdupois pound) ton used in the US, rather than to the old imperial long ton. The metric ton (2000 kg.) is always called the tonne. Before discussing each tabulation in detail, there is a brief discussion of the systems of units. .3 The SI system (BIPM, 1981; UNESCO, 1985) The SI system of units is the modern version of the metric system which has been universally adopted by scientists. Details of the system are given in BIPM (1981) and numerous documents published by national authorities. In preparing the series of environmental tables I have relied heavily on UNESCO (1985). Only a brief summary is given here. The SI system is an extension of the MKS system, where the acronym stands for metre, kilogram, second. These are the base units for length, mass and time respectively and have the symbols m, kg and s. Other quantities and their units are built from the base quantities and units. These are called derived units and many have received a special name. For example, energy expressed in SI base units has units m^2.kg.s^-2 which has been given the name joule, and the abbreviation J. .4 The metric system The idea of the metric system (also used in SI) is that prefixes are used to form decimal multiples and submultiples of units. The most common ones are mega-(M) for 10^6, kilo-(k) for 10^3, hecto-(h) for 100, centi-(c) for 0.01, milli-(m) for 10^-2 and micro-(u) for 10^-6. Note that the proper abbreviation for micro is the greek mu. The closest letter on the keyboard, is u, which, if entered as a metric prefix is taken as micro. These conversion tables will recognise all of these prefixes as well as deci- (d) for 0.1 The SI system encourages only a restricted set of units. Thus the hectare - a perfectly acceptable metric unit - is strongly discouraged under the SI system. Firstly the are (which is 100 square metres) is not a recognised SI unit. Secondly, the SI system prefers quantities in multiple of 10^3. Thirdly, the symbol ha, which is normally used for hectares, is actually hectoannum (i.e. 100 years) in the SI system. .5 The United States system The US system of weights and measures is based on the British Imperial system. The units of mass, length and time are the pound, yard and second respectively. These are multiplied or subdivided into units which have different names - and are always based on non-decimal multiples. Representing units All of the entries in this item require you to give a value and its units and conversion is based on the units that you entered. You will be given examples of the preferred form for the units, but the program will try hard to interpret your entry. For example, J/(s ft^2) is preferred but J/(ft^2 s), J ft^-2 s^-1 and J s^-1 ft^-2 are all understood. The program will try to interpret some incorrect entries. Thus an entry of 6MM as a length will assume that entry was inadvertently in capitals and use 6 millimetres but 6Mm will be taken as 6 megametres. .6 Temperature The unit of thermodynamic temperature is an SI base unit. It has the name kelvin and the symbol K. This unit and name are also used to express an interval or difference of temperature. The Celsius temperature (t) is defined in terms of the thermodynamic temperature (T) by t = T - 273.15 The unit "degree Celsius" equals the unit "kelvin" but expresses a Celsius temperature. Because of the absence of a degree sign on computer keyboards, the symbol C is used. The US system of temperature is based on the Fahrenheit as a unit for which the symbol F is used. A Fahrenheit temperature (F) is related to the Celsius temperature by F - 32 = 1.8 t The International Committee for Weights and Measures at its September 1989 meeting approved the use of ITS-90: The International Temperature Scale of 1990. In this scale the triple point of water is at 273.16K but the boiling point of water at 1013.25hPa is 99.974C. .7 Pressure The following are converted: (abbreviations in brackets) bar [ba] - and all its metric prefixes Pascal [Pa] - and all its metric prefixes. Mass per area - any acceptable mass (imperial or metric) divided by any acceptable area (imperial or metric) The mass is taken as a force Length Hg- The height of a mercury column [e.g. 760mmHg or 29.92inHg] Length H2O - The height of a water column [e.g. 9ftH2O or 3mH2O] barye [barye] - must be entered like this dyne per area - e.g 5dyne/cm^2. Do not abbreviate dyne newton [N] per area - e.g. 5N/m^2 or 5N m^-2 Notes: See the appropriate pages for acceptable mass, length and area entries. Any unidentified length is treated as the height of a mercury colum. .8 Pressure conversions The conversions are given in the following units: bar, decibar, kPa, millibar (i.e. hPa), Pascal (i.e. N/m^2), kg/cm^2, kg/m^2, mmHg (i.e. Torr), inch Hg, psi (i.e. pounds per square inch), atmospheres, barye which is the same as dyne/cm^2, cmH2O, ftH2O, ton/ft^2, N/cm^2. At the first prompt for a value, pressing the Enter key on its own will be taken as 1 atmosphere (1013.25 hPa). At subsequent prompts, pressing the Enter key on its own indicates that the tabulation is complete. The length conversions (water and mercury) are based on a temperature of 0C. The mass conversions use the conventional standard value for gravity acceleration of g = 9.80665 .9 Length The following lengths are converted: The metre and any of its seven common prefixes. Thus Mm, km, hm, m, dm, cm, mm, um are all recognised units. Imperial units of inch [in], foot[ft], yard[yd], chain[ch], mile[mi]. Combinations of imperial units are accepted so that 1ft12in is treated the same as 2ft. The abbreviations 1'12" can also be used. The United States uses two definitions of the yard. For industrial and scientific purposes the American Standards Association has adopted the yard defined as 0.9144 m exactly. This is the one used in these tables. However, the US yard, which is primarily used for land-surveying is defined as 3600/3937 m. .10 Area You may enter the square of any of the length units except for the chain, plus units of acres [ac] where an acre is 10 square chains. Because the metric unit of area is the are [a], which is 100m^2, metric prefixes to this are also recognised. Thus 6ac is recognised as 6 acres but 6ca is 6 centi-ares. The abbreviation for powers follows that of Basic. Thus m^2 represents square metres. However sq. is also recognised for square so that an alternate form of 1m^2 is 1sq. m In the SI system a combination of prefix and symbol for a unit is regarded as a single symbol which may be raised to a power without brackets. Thus 1 cm^2 always means (0.01 m)^2 and never 0.01 m^2. Because 1 m^2 is a centare [ca] this last unit could be written as 0.01 ca. Remember that the are [a], though a metric unit, is not an SI unit. Conversions are given in square inches, feet, yards, miles, m^2, mm^2, cm^2, km^2, acres and hectares. .11 Volume You may enter the cube of any of the length units except for the chain as powers (e.g. 2.4m^3) or using cu. for cubic (e.g. 2.4cu. m, 1in^3). There are two other metric (but not SI) units of volume. The litre [l], which is 1dm^3, and the stere [s], which is 1m^3. Both of these, and their common metric prefixes are accepted. In addition, the common (though incorrect) abbreviation cc is recognised as cm^3. You may also enter US liquid measures as ounces [oz], quarts [qt] or gallons [gal] or any combination of these three. For example, 1gal3qt2oz. Finally, this item recognises three special hydrological units. The acre-foot [af] (an area of 1 acre covered with a foot of water), the second-foot day [sfd] which is the volume of water in a flow of one second-foot (i.e. 1ft^3/s) over one day. A metric (non-SI) version of this is the cumec-day [cmd] which is the volume of water in a flow of one cumec (i.e. 1m^3/s) over one day. Conversions are given in m^3, ft^3, in^3, gal, qt, oz, af, sfd, cmd, cm^3, litres and Ml (megalitres). .12 Speed Any length unit per second [s], minute [min], hour [h] or day [d] expressed using either powers, or with a slash is acceptable. E.g. 6m s^-1, 8mi/h. Also you may enter knots without abbreviation. The knot is one nautical mile per hour and has been universally agreed to as 1852 metres per hour. If you need to convert to or from length units of nautical miles then it can be done using this table. Conversions are given as knots, then as length per time where the output lengths are m, km, in, ft, y, mi and the times are s, min, h, d. Flow Accepts any volume unit per second [s], minute [min], hour [h] or day [d] and converts it to outputs of volume per time where the volumes are m^3, ft^3, in^3, gal, qt, oz, af, sfd, cmd, cm^3, l, Ml and the times are s, min, h, d. .13 Mass The SI unit of mass is the kilogram [kg]. Because this already has a metric prefix, and the SI system does not allow double prefixes, all metric units of mass add prefixes to the gram [g]. The common ones are all acceptable, as are the metric ton [tonne], and the avoirdupois ounce [oz], pound [lb] and ton [ton] - where ton is taken as the short ton of 2000lb. Conversion is to kg, lb, oz, ton, tonne, g. Mass transport Accepts any mass unit per second [s], minute [min], hour [h] or day [d] and converts it to outputs of mass per time where the conversion of mass units is as given above and all four time units are used. Density Accepts any mass per volume, where the acceptable mass units and volume units are as given above. There are thus 420 acceptable units. Conversion is to kg/m^3, g/cm^3 and lb/ft^3. .14 Energy The SI unit of energy is the joule [J] and its use has rendered obsolete both the erg and the calorie. One problem with the calorie was that there were a number of different definitions (and hence values) for it. These conversion tables use the International Table calorie (IT calorie) of 4.18684 J. A fourth metric unit of energy is recognised by this item. The kilowatt-hour [kWh]. Imperial units of energy that are accepted are the British thermal unit [BTU] and the foot-pound [ft-lb]. Conversion then takes place between these units and the four metric units. Power The SI unit is the watt [W] which is the power dissipated by one joule per second. The imperial unit is the horsepower [HP] which is 550 ft-lb/s. This item accepts a power in either of these units or as an energy per second [s], minute [min], hour [h] or day [d] and converts between them all. .15 Energy flux This is the energy per unit area per unit time. In the SI system it has units of W/m^2. This item recognises any acceptable power divided by an acceptable area, or an energy divided by an area and a time. Use the form J/(m^2 s) or J/(s m^2). It is incorrect to use double slashes as in J/m^2/s and this will not be recognised. Conversion is to W/m2, HP/ft^2, mW/m^2, W/ft^2, W/in^2, and to J/m^2, BTU/ft^2, BTU/in^2, cal/m^2, cal/cm^2 per second [s], minute [min], hour [h] or day [d] . Specific heat capacity Both the calorie and the BTU are defined in terms of the amount of heat required to increase the temperature of water. The relation 1 BTU/(lb F) = 1 IT cal/(g C) has been used for conversion. This item recognises any acceptable energy, mass unit, or temperature unit and converts to J/(kg K), BTU/(lb F), erg/(g K), cal/(g K), ft-lb/(lb F) and cal/(kg K). .16 References BIPM (Bureau International des Poids et Mesures), Le Systeme International d'Unites (SI), 4th edition, 1981. (An english translation was prepared jointly by the UK National Physical Laboratory and the US National Bureau of Standards). UNESCO, The International System of Units (SI) in Oceanography, Technical paper in marine science No. 45, (IAPSO publication No. 32), Unesco, Paris, 1985. --------------------------------------------------------------- REMINDER This program is being distributed as shareware to publicise the Applied Environmetrics Hydrological Tables. It forms one of the eighteen items that make up these tables. Applied Environmetrics publishes computer-based environmental and scientific tables and is looking for authors. For further information write to Applied Environmetrics 118 Gordon St. PO Box 241 Balwyn, Vic. 3103 Roslyn, WA Australia USA 98941-0241 Phone (03)-8172571 Ph: (509) 649 2940