Ellipsoid, semiMajorAxis, secondDefiningParameter Geodetic datum .1 GeodeticDatum

120 Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. element name=secondDefiningParameter complexType sequence element ref=gml:SecondDefiningParameter sequence complexType element element name=SecondDefiningParameter complexType choice element name=inverseFlattening type=gml:MeasureType element name=semiMinorAxis type=gml:LengthType element name=isSphere type=boolean default=true choice complexType element gml:secondDefiningParameter is a property containing the definition of the second parameter that defines the shape of an ellipsoid. An ellipsoid requires two defining parameters: semi-major axis and inverse flattening or semi-major axis and semi-minor axis. When the reference body is a sphere rather than an ellipsoid, only a single defining parameter is required, namely the radius of the sphere; in that case, the semi-major axis degenerates into the radius of the sphere. The gml:inverseFlattening element contains the inverse flattening value of the ellipsoid. This value is a scale factor or ratio. It uses gml:LengthType with the restriction that the unit of measure referenced by the uom attribute must be suitable for a scale factor, such as percent, permil, or parts-per-million. The gml:semiMinorAxis element contains the length of the semi-minor axis of the ellipsoid. When the gml:isSphere element is included, the ellipsoid is degenerate and is actually a sphere. The sphere is completely defined by the semi-major axis, which is the radius of the sphere.

12.5.3.6 EllipsoidPropertyType

complexType name=EllipsoidPropertyType sequence minOccurs=0 element ref=gml:Ellipsoid sequence attributeGroup ref=gml:AssociationAttributeGroup complexType gml:EllipsoidPropertyType is a property type for association roles to an ellipsoid, either referencing or containing the definition of that ellipsoid.

12.5.3.7 PrimeMeridian, greenwichLongitude

element name=PrimeMeridian type=gml:PrimeMeridianType substitutionGroup=gml:Definition complexType name=PrimeMeridianType complexContent extension base=gml:IdentifiedObjectType sequence element ref=gml:greenwichLongitude sequence extension complexContent complexType Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. 121 A gml:PrimeMeridian defines the origin from which longitude values are determined. The default value for the prime meridian gml:identifier value is Greenwich. element name=greenwichLongitude type=gml:AngleType gml:greenwichLongitude is the longitude of the prime meridian measured from the Greenwich meridian, positive eastward. If t he value of the prime meridian ―name‖ is Greenwich then the value of greenwichLongitude shall be 0 degrees. The property uses gml:AngleType.

12.5.3.8 PrimeMeridianPropertyType

complexType name=PrimeMeridianPropertyType sequence minOccurs=0 element ref=gml:PrimeMeridian sequence attributeGroup ref=gml:AssociationAttributeGroup complexType gml:PrimeMeridianPropertyType is a property type for association roles to a prime meridian, either referencing or containing the definition of that meridian. 12.5.4 Other concrete datums 12.5.4.1 EngineeringDatum element name=EngineeringDatum type=gml:EngineeringDatumType substitutionGroup=gml:AbstractDatum complexType name=EngineeringDatumType complexContent extension base=gml:AbstractDatumType complexContent complexType gml:EngineeringDatum defines the origin of an engineering coordinate reference system, and is used in a region around that origin. This origin may be fixed with respect to the Earth such as a defined point at a construction site, or be a defined point on a moving vehicle such as on a ship or satellite.

12.5.4.2 EngineeringDatumPropertyType

complexType name=EngineeringDatumPropertyType sequence minOccurs=0 element ref=gml:EngineeringDatum sequence attributeGroup ref=gml:AssociationAttributeGroup complexType gml:EngineeringDatumPropertyType is a property type for association roles to an engineering datum, either referencing or containing the definition of that datum.

12.5.4.3 ImageDatum

element name=ImageDatum type=gml:ImageDatumType substitutionGroup=gml:AbstractDatum complexType name=ImageDatumType complexContent extension base=gml:AbstractDatumType