ConventionalUnit, ConventionalUnitType Units schema

Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. 181 choice element name=factor type=double element name=formula type=gml:FormulaType choice extension complexContent complexType The inherited attribute uom references the preferred unit that this conversion applies to. The conversion of a unit to the preferred unit for this physical quantity type is specified by an arithmetic conversion scaling andor offset. The content model extends gml:UnitOfMeasureType, which has a mandatory attribute uom which identifies the preferred unit for the physical quantity type that this conversion applies to. The conversion is specified by a choice of  gml:factor, which defines the scale factor, or  gml:formula, which defines a formula by which a value using the conventional unit of measure can be converted to obtain the corresponding value using the preferred unit of measure. The model for the formula is given as follows: complexType name=FormulaType sequence element name=a type=double minOccurs=0 element name=b type=double element name=c type=double element name=d type=double minOccurs=0 sequence complexType This formula defines the parameters of a simple formula by which a value using the conventional unit of measure can be converted to the corresponding value using the preferred unit of measure. The formula element contains elements a, b, c and d, whose values use the XML Schema type double. These values are used in the formula y = a + bx c + dx, where x is a value using this unit, and y is the corresponding value using the base unit. The elements a and d are optional, and if values are not provided, those parameters are considered to be zero. If values are not provided for both a and d, the formula is equivalent to a fraction with numerator and denominator parameters.

16.2.12 Example of units dictionary informative

This dictionary contains definitions corresponding to all the base and derived units defined by in the SI system [SI], plus a selection of conventional units to illustrate the usage of these components. gml:Dictionary gml:id=unitsDictionary gml:descriptionA dictionary of units of measuregml:description gml:identifier codeSpace=http:www.opengeospatial.orginitiatives?iid=79OWS-1.2 Unitsgml:identifier gml:dictionaryEntry gml:Dictionary gml:id=SIBaseUnits gml:descriptionThe Base Units from the SI units system.gml:description gml:identifier codeSpace=http:www.opengeospatial.orginitiatives?iid=79OWS-1.2 SI Base Unitsgml:identifier gml:dictionaryEntry gml:BaseUnit gml:id=m gml:descriptionThe metre is the length of the path travelled by light in vacuum during a time interval of 1299 792 458 of a second.gml:description gml:identifier codeSpace=http:www.bipm.fren3_SIbase_units.htmlmetregml:identifier gml:name xml:lang=enUSmetergml:name gml:quantityTypelengthgml:quantityType 182 Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. gml:catalogSymbol codeSpace=http:www.bipm.fren3_SIbase_units.htmlmgml:catalogSymbol gml:unitsSystem xlink:href=http:www.bipm.fren3_SI gml:BaseUnit gml:dictionaryEntry -- … -- gml:Dictionary gml:dictionaryEntry gml:dictionaryEntry gml:Dictionary gml:id=SIDerivedUnits gml:descriptionThe Derived Units from the SI units system. These are all derived as a product of SI Base Units, except degrees Celsius in which the conversion formaula to the SI Base Unit kelvin involves an offset. gml:description gml:identifier codeSpace=http:www.opengeospatial.orginitiatives?iid=79OWS-1.2 SI Derived Unitsgml:identifier gml:dictionaryEntry gml:DerivedUnit gml:id=rad gml:identifier codeSpace=http:www.bipm.fren3_SIradiangml:identifier gml:quantityTypeplane anglegml:quantityType gml:catalogSymbol codeSpace=http:www.bipm.fren3_SIradgml:catalogSymbol gml:derivationUnitTerm uom=m exponent=1 gml:derivationUnitTerm uom=m exponent=-1 gml:DerivedUnit gml:dictionaryEntry -- … -- gml:Dictionary gml:dictionaryEntry gml:dictionaryEntry gml:Dictionary gml:id=ConventionalUnitsDictionary gml:descriptionA collection of Conventional Units. These are units of measure which are either widely used or important within a specific community. For most of these there is 1. a known derivation from more primitive units, which may or may not be SI Base Units, or 2. a known conversion to a preferred unit, which may or may not be an SI Base or Derived unit, through rescaling and offset, or both.gml:description gml:identifier codeSpace=http:www.opengeospatial.orginitiatives?iid=79OWS-1.2 Conventional units.gml:identifier gml:dictionaryEntry gml:DerivedUnit gml:id=m3 gml:identifier codeSpace=http:www.opengeospatial.orginitiatives?iid=79cubic metregml:identifier gml:quantityTypeVolumegml:quantityType gml:derivationUnitTerm uom=m exponent=3 gml:DerivedUnit gml:dictionaryEntry gml:dictionaryEntry gml:ConventionalUnit gml:id=l gml:identifier codeSpace=http:www.opengeospatial.orginitiatives?iid=79litregml:identifier gml:quantityTypeVolumegml:quantityType gml:conversionToPreferredUnit uom=m3 gml:factor0.001gml:factor gml:conversionToPreferredUnit gml:ConventionalUnit gml:dictionaryEntry -- … -- gml:Dictionary gml:dictionaryEntry gml:Dictionary

16.3 Measures schema

16.3.1 Overview

gml:MeasureType is defined in the basicTypes schema. The measure types defined here correspond with a set of convenience measure types described in ISOTS 19103. The XML implementation is based on the XML