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A unit of measurement is a definite magnitude of a physical quantity, defined and adopted by convention or by law, that is used as a standard for measurement of the same physical quantity. Any other value of the physical quantity can be expressed as a simple multiple of the unit of measurement. For example, length is a physical quantity, and metre meter is a unit of length that represents a definite predetermined length.
The node <units> in the *.spd file can be used to change some defaults or to add specialized units, which in principle are not supported. The structure and contents of this subtree <units> requires to have the format as further detailed in this document. The following attributes are available:
n - name
pn - printed name (decorated and translated)
p - Priority of the unit, it is regarded as more important than others units. The possible values for 'p' are 1, 2 and 3, as follows,
1 - It gives maximum priority, and therefore a unit with p="1" is the default unit in the GUI.
2 - A unit with p="2" is always shown in the combobox of below to facilitate the selection of the most used units.
3 - It gives lowest priority, and therefore a unit with p="3" could only be chosen when clicking on 'More units...' option in the combobox of below, which enables the user to choose the unit from a table.
factor - The conversion factor used to multiply a quantity when converting from one system of units to another. It is the mathematical tool for converting between units of measurement [1 unit=factor*unit(SI)]. Example: 1mm=10e-3 m.
help - To make easier to the user to identify the unit.
Example of <units> field: Species concentration and reference variable are not supported and therefore, both magnitudes are defined in the *.spd file, as follows,
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