BaseUnit, BaseUnitType, unitsSystem Units schema

180 Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. element name=derivationUnitTerm type=gml:DerivationUnitTermType complexType name=DerivationUnitTermType complexContent extension base=gml:UnitOfMeasureType attribute name=exponent type=integer extension complexContent complexType This unit term references another unit of measure uom and provides an integer exponent applied to that unit in defining the compound unit. The exponent may be positive or negative, but not zero.

16.2.10 ConventionalUnit, ConventionalUnitType

Conventional units that are neither base units nor defined by direct combination of base units are used in many application domains. For example electronVolt for energy, feet and nautical miles for length. In most cases there is a known, usually linear, conversion to a preferred unit which is either a base unit or derived by direct combination of base units. The gml:ConventionalUnit element is declared as follows: element name=ConventionalUnit type=gml:ConventionalUnitType substitutionGroup=gml:UnitDefinition complexType name=ConventionalUnitType complexContent extension base=gml:UnitDefinitionType sequence choice element ref=gml:conversionToPreferredUnit element ref=gml:roughConversionToPreferredUnit choice element ref=gml:derivationUnitTerm minOccurs=0 maxOccurs=unbounded sequence extension complexContent complexType The gml:ConventionalUnit extends gml:UnitDefinition with a property that describes a conversion to a preferred unit for this physical quantity. When the conversion is exact, the element gml:conversionToPreferredUnit should be used, or when the conversion is not exact the element gml:roughConversionToPreferredUnit is available. Both of these elements have the same content model. The gml:derivationUnitTerm property defined above is included to allow a user to optionally record how this unit may be derived from other more primitive units. 16.2.11 conversionToPreferredUnit, roughConversionToPreferredUnit, ConversionToPreferredUnitType, FormulaType The elements gml:conversionToPreferredUnit and gml:roughConversionToPreferredUnit represent parameters used to convert conventional units to preferred units for this physical quantity type. A preferred unit is either a Base Unit or a Derived Unit that is selected for all values of one physical quantity type. These conversions are declared in the schema as follows: element name=conversionToPreferredUnit type=gml:ConversionToPreferredUnitType element name=roughConversionToPreferredUnit type=gml:ConversionToPreferredUnitType complexType name=ConversionToPreferredUnitType complexContent extension base=gml:UnitOfMeasureType