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UnitConversions are defined to map internal units to external units. For each unit to be converted, the conversion method can be defined. This may be a simple multiplication (e.g. feet to metres), as well as a possible increment (e.g. o F to o C). The converted value is (inputUnitTypeValue * multiplier) + increment. In DELFT-FEWS the convention for storing level data is that this is with reference to the local datum. If the external unit specifies the datum is global, a Boolean flag can be used to indicate the data should be converted on import.
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