This page covers the standards used in this project for the web site and the developed application.

Character Set

The character set used in the web pages and applications is UTF-8, as promoted by

Unicode is an attempt to create a common standard for representing all known languages, and most known character sets are subsets of the very large Unicode character set. Although there are multiple character encodings available for Unicode, the most common is UTF-8, which has the advantage of being backwards-compatible with ASCII: that is, every ASCII text file is also a UTF-8 text file with identical meaning.

Files in this project are saved as far as possible with Unicode normalisation form = none, and without any Unicode BOM signature in the file header as this can cause issues opening the file under different operating systems.

Microsoft MS-DOS and Windows use a common text file format, with each line of text separated by a two character combination: CR and LF, which have ASCII codes 13 and 10. It is common for the last line of text not to be terminated with a CR-LF marker, and many text editors (including Notepad) do not automatically insert one on the last line.

Most Windows text files use a form of ANSI, OEM or Unicode encoding. What Windows terminology calls "ANSI encodings" are usually single-byte ISO-8859 encodings, but as far as this project goes we are using the basic standard ASCII / UTF8 character set as far as possible.

W3C Validator tool usually displays the following message when UTF-8 is specified in the HTML but the physical file does not match:
  "Byte-Order Mark found in UTF-8 File.The Unicode Byte-Order Mark (BOM) in UTF-8 encoded files is known to cause problems for some text editors and older browsers. You may want to consider avoiding its use until it is better supported. "

The BOM consists of three bytes at the start of the file with hex values 'EF BB BF'. If other files containing data such as CSV data files, are saved in this format they may load with strange characters at the start.


This web site and the web based application it supports use the W3C standard. All HTML pages (x.HTML files) use

XHTML 1.0 Transitional standard and are validated using the W3C validator tool.

Cascading style sheets are validated using the W3C css validator.

For XHTML tags and Javascript see Visit W3Schools as our recommended reference web site, used in this project.

Search Engines

The web site contains a robots.txt file as described at and following the Google web master tools standard.

The web site also contains a sitemap.xml file generated via as specified under the Google web master tools standard

The underlying web based application uses XHTML and Javascript, but as the application is not a web site and does not follow 'site' standards, the directories are excluded from crawling in the robots.txt file.
Individual application html pages also include the standard <META NAME="ROBOTS" CONTENT="NOINDEX, NOFOLLOW"> code

Units of Measurement

Where ever possible we will be using standard units in this project as described below.  Standard symbols to represent values will also be used. Application code will use standard names for variables and constants throughout different programs.  Other units 'accepted' in the SI system, but not of use in this project may not be included below.

The international system of units consists of a set of units together with a set of prefixes. The units of SI can be divided into two subsets. There are seven base units. Each of these base units is nominally dimensionally independent. From these seven base units several other units are derived. In addition to the SI units there is also a set of non-SI units accepted for use with SI.

For information check the National Physical Laboratory definitions page Measurement Units
SI base units
Name Symbol Quantity
metre m length
kilogram kg mass
second s time
ampere A electric current
kelvin K thermodynamic temperature
mole mol amount of substance
candela cd luminous intensity

A prefix may be added to a unit to produce a multiple of the original unit. All multiples are integer powers of ten. For example, kilo- denotes a multiple of a thousand and milli- denotes a multiple of a thousandth; hence there are one thousand millimetres to the metre and one thousand metres to the kilometre. The prefixes are never combined: a millionth of a kilogram is a milligram not a microkilogram.

Standard prefixes for the SI units of measure
Multiples Name   deca- hecto- kilo- mega- giga- tera- peta- exa- zetta- yotta-
Symbol   da h k M G T P E Z Y
Factor 100 101 102 103 106 109 1012 1015 1018 1021 1024
Subdivisions Name   deci- centi- milli- micro- nano- pico- femto- atto- zepto- yocto-
Symbol   d c m   n p f a z y
Factor 100 10-1 10-2 10-3 10-6 10-9 10-12 10-15 10-18 10-21 10-24

The International Organisation for Standardisation document ISO 31 contains recommendations for the use of the International System of Units; together with IEC 60027 for electrical engineering.

A new standard ISO 80000 is now in progress to combine both standards in a joint standard in which the quantities and equations used with SI are to be referred as the International System of Quantities (ISQ).

It is a widely respected style guide for the use of physical quantities and units of measurement, and formulas involving them, in scientific and educational documents worldwide. In most countries, the notations used in mathematics and science textbooks at schools and universities follow closely the guidelines given by these standards.

Very few of the above prefixes appear in scientific work, as scientific notation of some value to a power of 10 is normally used with a base unit, example 5.8 x 109 grams would not be expressed as 5.8 gigagram but 5.8 x 106 kg.  Mega, giga and tera are used more in computing where the they are not exact anyway -  a kilobyte being 1024 bytes rather than a 1000 bytes, but we will not start going down that road here.  In Astronomy the largest measurements are distances and these can be in units based on special multiples of the base distance unit, e.g. light year, parsec, astronomical unit. This is mainly because of the large numbers involved and some of these units fit neatly into equations with other derived units to produce meaningful results.

Derived units

Base units can be put together to derive units of measurement for other quantities. In addition to the two dimensionless derived units radian (rad) and steradian (sr) there are 20 derived units having special names:

Named units derived from SI base units
Name Symbol Quantity Expression in terms of other units Expression in terms of SI base units
hertz Hz frequency 1/s s-1
newton N force, weight mkg/s2 mkgs-2
pascal Pa pressure, stress N/m2 m-1kgs-2
joule J energy, work, heat Nm = CV = Ws m2kgs-2
watt W power, radiant flux, luminosity Js-1 = VA m2kgs-3
volt V voltage, electrical potential difference, electromotive force W/A = J/C m2kgs-3A-1
weber Wb magnetic flux J/A m2kgs-2A-1
tesla T magnetic field Vs/m2 = Wb/m2 = N/(Am) kgs-2A-1
henry H inductance Vs/A = Wb/A m2kgs-2A-2
degree Celsius C temperature K - 273.15 K
lumen lm luminous flux cdsr cd
lux lx illuminance lm/m2 m-2cd

Other quantities and units

Compound units derived from SI units

Name Symbol Quantity Expression in terms
of SI base units
square metre m2 area m2
cubic metre m3 volume m3
metre per second m/s speed, velocity ms-1
cubic metre per second m3/s volumetric flow m3s-1
metre per second squared m/s2 acceleration ms-2
metre per second cubed m/s3 jerk ms-3
metre per quartic second m/s4 snap ms-4
radian per second rad/s angular velocity s-1
newton second Ns momentum, impulse kgms-1
newton metre second Nms angular momentum kgm2s-1
newton metre Nm torque, moment of force kgm2s-2
reciprocal metre m-1 wavenumber m-1
kilogram per cubic metre kg/m3 density, mass density kgm-3
cubic metre per kilogram m3/kg specific volume kg-1m3
mole per cubic metre mol/m3 amount (-of-substance) concentration m-3mol
cubic metre per mole m3/mol molar volume m3mol-1
joule per kelvin J/K heat capacity, entropy kgm2s-2K-1
joule per kelvin mole J/(Kmol) molar heat capacity, molar entropy kgm2s-2K-1mol-1
joule per kilogram kelvin J/(Kkg) specific heat capacity, specific entropy m2s-2K-1
joule per mole J/mol molar energy kgm2s-2mol-1
joule per kilogram J/kg specific energy m2s-2
joule per cubic metre J/m3 energy density kgm-1s-2
newton per metre N/m = J/m2 surface tension kgs-2
watt per square metre W/m2 heat flux density, irradiance kgs-3
watt per metre kelvin W/(mK) thermal conductivity kgms-3K-1
square metre per second m2/s kinematic viscosity, diffusion coefficient m2s-1
pascal second Pas = Ns/m2 dynamic viscosity kgm-1s-1
siemens per metre S/m conductivity kg-1m-3s3A2
siemens square metre per mole Sm2/mol molar conductivity kg-1s3mol-1A2
volt per metre V/m electric field strength kgms-3A-1
ampere per metre A/m magnetic field strength Am-1
candela per square metre cd/m2 luminance cdm-2

Non-SI units accepted for use with SI

The following units are not SI units but are "accepted for use with the International System."

Name Symbol Quantity Equivalent SI unit
minute min time (multiple unit) 1 min = 60 s
hour h time (multiple unit) 1 h = 60 min = 3600 s
day d time (multiple unit) 1 d = 24 h = 1440 min = 86400 s
degree of arc   angle (non unitary unit) 1 = (p/180) rad
minute of arc ' angle (non unitary unit) 1' = (1/60) = (p/10800) rad
second of arc ? angle (non unitary unit) 1? = (1/60)' = (1/3600) = (p/648000) rad
square degree deg or sq.deg. solid angle 1 deg = (p/180) sr. This unit is mostly used in astronomy and optic (its usage is strongly discouraged in all other domains, including in cartography). The whole sphere covers a solid angle (seen from its centre) of (129600/p) deg (approx. 41252.961 deg) and is the solid angle covered by a conic section of a sphere, whose opening apex is exactly 360 (note that the measure of a solid angle in square degrees is not proportional (and does not vary polynomially with) the measure of the associated planar angle in degrees of opening of its associated cone. In cartography, you can't simply multiply a difference of longitudes and a difference of latitudes, both expressed in degrees to get an exact measure of a solid angle in square degrees (this will just be an approximation only if these differences are very small, below one minute of arc each, and the covered area is very near the equator, i.e. at very low latitudes where the small area will be nearly rectangular instead of being nearly trapezoidal in median latitudes, or nearly a disc sector near the poles).
litre l or L volume (simple decimal multiple unit) 1 dm3 = 0.001 m3
tonne t mass (simple decimal multiple unit) 1 t = 103 kg = 1 Mg

Non-SI units with values obtained only by experiment
Name Symbol Quantity Equivalent SI unit
electronvolt eV energy 1 eV = 1.60217733 (49) 10-19 J
atomic mass unit u mass 1 u = 1.6605402 (10) 10-27 kg
astronomical unit AU length 1 AU = 1.49597870691 (30) 1011 m
Non-SI units whose use is not encouraged
Name Symbol Quantity Equivalent SI unit
ngstrm, angstrom   length 1 = 0.1 nm = 10-10 m
bar bar pressure 1 bar = 105 Pa
millibar mbar pressure 1 mbar = 1 hPa = 100 Pa (was used in atmospheric meteorology, the preferred unit is now the hectopascal)
atmosphere atm pressure 1 atm = 1013.25 mbar = 1013.25 hPa] = 1.01325105 Pa (commonly used in atmospheric meteorology, in oceanology and for pressures within liquids, or in the industry for pressures within containers of liquified gas)

Recommended Values of the Fundamental Constants

Values for constants in calculations follow standards recommended by the National Physical Laboratory ( and Kaye & Laby Online is a valuable resource.

These are sourced from CODATA Task Group on Fundamental Constants (Committee on Data for Science and Technology)

The latest values are available from the CODATA fundamental constants page at the American National Institute of Standards and Technology's web site (NIST)