Overview Coordinate reference systems

Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. 101 These schema components encode the Coordinate Reference System packages of the UML Models of ISO 19111:2007, Clause 8, and D.3.9 of this International Standard, with the exception of the abstract SC_CRS class. NOTE The coordinateReferenceSystems schema document includes the coordinateSystems.xsd, datums.xsd, and coordinateOperations.xsd GML schema documents. This schema document is identified by the following location-independent name using URN syntax: urn:x-ogc:specification:gml:schema-xsd:coordinateReferenceSystems:3.2.1 12.3.2 Abstract coordinate reference systems 12.3.2.1 AbstractSingleCRS element name=AbstractSingleCRS type=gml:AbstractCRSType abstract=true substitutionGroup=gml:AbstractCRS gml:AbstractSingleCRS implements a coordinate reference system consisting of one coordinate system and one datum as opposed to a Compound CRS.

12.3.2.2 SingleCRSPropertyType

complexType name=SingleCRSPropertyType sequence minOccurs=0 element ref=gml:AbstractSingleCRS sequence attributeGroup ref=gml:AssociationAttributeGroup complexType gml:SingleCRSPropertyType is a property type for association roles to a single coordinate reference system, either referencing or containing the definition of that coordinate reference system.

12.3.2.3 AbstractGeneralDerivedCRS

element name=AbstractGeneralDerivedCRS type=gml:AbstractGeneralDerivedCRSType abstract=true substitutionGroup=gml:AbstractSingleCRS complexType name=AbstractGeneralDerivedCRSType abstract=true complexContent extension base=gml:AbstractCRSType sequence element ref=gml:conversion sequence extension complexContent complexType gml:AbstractGeneralDerivedCRS is a coordinate reference system that is defined by its coordinate conversion from another coordinate reference system. This abstract complex type shall not be used, extended, or restricted, in a GML application schema, to define a concrete subtype with a meaning equivalent to a concrete subtype specified in this document.

12.3.2.4 Conversion

element name=conversion type=gml:GeneralConversionPropertyType 102 Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. gml:conversion is an association role to the coordinate conversion used to define the derived CRS. 12.3.3 Concrete coordinate reference systems 12.3.3.1 CompoundCRS element name=CompoundCRS type=gml:CompoundCRSType substitutionGroup=gml:AbstractCRS complexType name=CompoundCRSType complexContent extension base=gml:AbstractCRSType sequence element ref=gml:componentReferenceSystem minOccurs=2 maxOccurs=unbounded sequence attributeGroup ref=gml:AggregationAttributeGroup extension complexContent complexType gml:CompundCRS is a coordinate reference system describing the position of points through two or more independent coordinate reference systems. It is associated with a non-repeating sequence of two or more instances of SingleCRS.

12.3.3.2 ComponentReferenceSystem

element name=componentReferenceSystem type=gml:SingleCRSPropertyType The gml:componentReferenceSystem elements are an ordered sequence of associations to all the component coordinate reference systems included in this compound coordinate reference system. The gml:AggregationAttributeGroup should be used to specify that the gml:componentReferenceSystem properties are ordered.

12.3.3.3 CompoundCRSPropertyType

complexType name=CompoundCRSPropertyType sequence minOccurs=0 element ref=gml:CompoundCRS sequence attributeGroup ref=gml:AssociationAttributeGroup complexType gml:CompoundCRSPropertyType is a property type for association roles to a compound coordinate reference system, either referencing or containing the definition of that reference system.

12.3.3.4 GeodeticCRS

element name=GeodeticCRS type=gml:GeodeticCRSType substitutionGroup=gml:AbstractSingleCRS complexType name=GeodeticCRSType complexContent extension base=gml:AbstractCRSType sequence choice element ref=gml:ellipsoidalCS element ref=gml:cartesianCS element ref=gml:sphericalCS choice