13.1 Gml Topic Version1Published11/11/2016Topic Change HistoryFor StandardCOM v2.1 Notes: 13.1.1 AbstractCoordinateOperation gml:AbstractCoordinateOperation is a mathematical operation on coordinates that transforms or converts coordinates to another coordinate reference system. Many but not all coordinate operations (from CRS A to CRS B) also uniquely define the inverse operation (from CRS B to CRS A). In some cases, the operation method algorithm for the inverse operation is the same as for the forward algorithm, but the signs of some operation parameter values shall be reversed. In other cases, different algorithms are required for the forward and inverse operations, but the same operation parameter values are used. If (some) entirely different parameter values are needed, a different coordinate operation shall be defined. 13.1.2 AbstractCoordinateOperationType 13.1.3 AbstractCoordinateSystem gml:AbstractCoordinateSystem is a coordinate system (CS) is the non-repeating sequence of coordinate system axes that spans a given coordinate space. A CS is derived from a set of mathematical rules for specifying how coordinates in a given space are to be assigned to points. The coordinate values in a coordinate tuple shall be recorded in the order in which the coordinate system axes associations are recorded. This abstract complex type shall not be used, extended, or restricted, in an Application Schema, to define a concrete subtype with a meaning equivalent to a concrete subtype specified in this document. 13.1.4 AbstractCoordinateSystemType 13.1.5 AbstractCRS gml:AbstractCRS specifies a coordinate reference system which is usually single but may be compound. 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. 13.1.6 AbstractCRSType 13.1.7 AbstractDatum A gml:AbstractDatum specifies the relationship of a coordinate system to the earth, thus creating a coordinate reference system. A datum uses a parameter or set of parameters that determine the location of the origin of the coordinate reference system. Each datum subtype may be associated with only specific types of coordinate systems. 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. 13.1.8 AbstractDatumType 13.1.9 AbstractGeneralConversion gm:AbstractGeneralConversion is an abstract operation on coordinates that does not include any change of datum. The best-known example of a coordinate conversion is a map projection. The parameters describing coordinate conversions are defined rather than empirically derived. Note that some conversions have no parameters. The operationVersion, sourceCRS, and targetCRS elements are omitted in a coordinate conversion. 13.1.10 AbstractGeneralConversionType 13.1.11 AbstractGeneralDerivedCRS 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. 13.1.12 AbstractGeneralDerivedCRSType 13.1.13 AbstractGML The abstract element gml:AbstractGML is "any GML object having identity". It acts as the head of an XML Schema substitution group, which may include any element which is a GML feature, or other object, with identity. This is used as a variable in content models in GML core and application schemas. It is effectively an abstract superclass for all GML objects. 13.1.14 AbstractGMLType 13.1.15 AbstractObject This element has no type defined, and is therefore implicitly (according to the rules of W3C XML Schema) an XML Schema anyType. It is used as the head of an XML Schema substitution group which unifies complex content and certain simple content elements used for datatypes in GML, including the gml:AbstractGML substitution group. 13.1.16 AbstractOperation 13.1.17 AbstractSingleCRS gml:AbstractSingleCRS implements a coordinate reference system consisting of one coordinate system and one datum (as opposed to a Compound CRS). 13.1.18 AbstractSingleOperation gml:AbstractSingleOperation is a single (not concatenated) coordinate operation. 13.1.19 AbstractTimeObject gml:AbstractTimeObject acts as the head of a substitution group for all temporal primitives and complexes. 13.1.20 AbstractTimeObjectType 13.1.21 AbstractTimePrimitive gml:AbstractTimePrimitive acts as the head of a substitution group for geometric and topological temporal primitives. 13.1.22 AbstractTimePrimitiveType 13.1.23 AggregationAttributeGroup A GML Object Collection is any GML Object with a property element in its content model whose content model is derived by extension from gml:AbstractMemberType. 13.1.24 AggregationType 13.1.25 anchorDefinition gml:anchorDefinition is a description, possibly including coordinates, of the definition used to anchor the datum to the Earth. Also known as the "origin", especially for engineering and image datums. The codeSpace attribute may be used to reference a source of more detailed on this point or surface, or on a set of such descriptions. 13.1.26 AngleType 13.1.27 anyURI 13.1.28 AssociationAttributeGroup XLink components are the standard method to support hypertext referencing in XML. An XML Schema attribute group, gml:AssociationAttributeGroup, is provided to support the use of Xlinks as the method for indicating the value of a property by reference in a uniform manner in GML. 13.1.29 axis The gml:axis property is an association role (ordered sequence) to the coordinate system axes included in this coordinate system. The coordinate values in a coordinate tuple shall be recorded in the order in which the coordinate system axes associations are recorded, whenever those coordinates use a coordinate reference system that uses this coordinate system. The gml:AggregationAttributeGroup should be used to specify that the axis objects are ordered. 13.1.30 axisAbbrev gml:axisAbbrev is the abbreviation used for this coordinate system axis; this abbreviation is also used to identify the coordinates in the coordinate tuple. The codeSpace attribute may reference a source of more information on a set of standardized abbreviations, or on this abbreviation. 13.1.31 axisDirection gml:axisDirection is the direction of this coordinate system axis (or in the case of Cartesian projected coordinates, the direction of this coordinate system axis at the origin). 13.1.32 baseGeodeticCRS gml:baseGeodeticCRS is an association role to the geodetic coordinate reference system used by this projected CRS. 13.1.33 CartesianCS gml:CartesianCS is a 1-, 2-, or 3-dimensional coordinate system. In the 1-dimensional case, it contains a single straight coordinate axis. In the 2- and 3-dimensional cases gives the position of points relative to orthogonal straight axes. In the multi-dimensional case, all axes shall have the same length unit of measure. A CartesianCS shall have one, two, or three gml:axis property elements. 13.1.34 cartesianCS gml:cartesianCS is an association role to the Cartesian coordinate system used by this CRS. 13.1.35 CartesianCSPropertyType gml:CartesianCSPropertyType is a property type for association roles to a Cartesian coordinate system, either referencing or containing the definition of that coordinate system. 13.1.36 CartesianCSType 13.1.37 CodeType gml:CodeType is a generalized type to be used for a term, keyword or name. 13.1.38 CodeWithAuthorityType gml:CodeWithAuthorityType requires that the codeSpace attribute is provided in an instance. 13.1.39 conversion gml:conversion is an association role to the coordinate conversion used to define the derived CRS. 13.1.40 coordinateOperationAccuracy gml:coordinateOperationAccuracy is an association role to a DQ_PositionalAccuracy object as encoded in ISO/TS 19139, either referencing or containing the definition of that positional accuracy. That object contains an estimate of the impact of this coordinate operation on point accuracy. That is, it gives position error estimates for the target coordinates of this coordinate operation, assuming no errors in the source coordinates. 13.1.41 CoordinateSystemAxis gml:CoordinateSystemAxis is a definition of a coordinate system axis. 13.1.42 CoordinateSystemAxisPropertyType gml:CoordinateSystemAxisPropertyType is a property type for association roles to a coordinate system axis, either referencing or containing the definition of that axis. 13.1.43 CoordinateSystemAxisType 13.1.44 CRSPropertyType gml:CRSPropertyType is a property type for association roles to a CRS abstract coordinate reference system, either referencing or containing the definition of that CRS. 13.1.45 Definition The basic gml:Definition element specifies a definition, which can be included in or referenced by a dictionary. 13.1.46 DefinitionBaseType 13.1.47 DefinitionType 13.1.48 description The value of this property is a text description of the object. gml:description uses gml:StringOrRefType as its content model, so it may contain a simple text string content, or carry a reference to an external description. The use of gml:description to reference an external description has been deprecated and replaced by the gml:descriptionReference property. 13.1.49 descriptionReference The value of this property is a remote text description of the object. The xlink:href attribute of the gml:descriptionReference property references the external description. 13.1.50 domainOfValidity The gml:domainOfValidity property implements an association role to an EX_Extent object as encoded in ISO/TS 19139, either referencing or containing the definition of that extent. 13.1.51 double 13.1.52 ellipsoid gml:ellipsoid is an association role to the ellipsoid used by this geodetic datum. 13.1.53 Ellipsoid A gml:Ellipsoid is a geometric figure that may be used to describe the approximate shape of the earth. In mathematical terms, it is a surface formed by the rotation of an ellipse about its minor axis. 13.1.54 ellipsoidalCS gml:ellipsoidalCS is an association role to the ellipsoidal coordinate system used by this CRS. 13.1.55 EllipsoidalCS gml:EllipsoidalCS is a two- or three-dimensional coordinate system in which position is specified by geodetic latitude, geodetic longitude, and (in the three-dimensional case) ellipsoidal height. An EllipsoidalCS shall have two or three gml:axis property elements; the number of associations shall equal the dimension of the CS. 13.1.56 EllipsoidalCSPropertyType gml:EllipsoidalCSPropertyType is a property type for association roles to an ellipsoidal coordinate system, either referencing or containing the definition of that coordinate system. 13.1.57 EllipsoidalCSType 13.1.58 EllipsoidPropertyType gml:EllipsoidPropertyType is a property type for association roles to an ellipsoid, either referencing or containing the definition of that ellipsoid. 13.1.59 EllipsoidType 13.1.60 GeneralConversionPropertyType gml:GeneralConversionPropertyType is a property type for association roles to a general conversion, either referencing or containing the definition of that conversion. 13.1.61 GeodeticCRS 13.1.62 GeodeticCRSPropertyType gml:GeodeticCRSPropertyType is a property type for association roles to a geodetic coordinate reference system, either referencing or containing the definition of that reference system. 13.1.63 GeodeticCRSType gml:GeodeticCRS is a coordinate reference system based on a geodetic datum. 13.1.64 geodeticDatum gml:geodeticDatum is an association role to the geodetic datum used by this CRS. 13.1.65 GeodeticDatum gml:GeodeticDatum is a geodetic datum defines the precise location and orientation in 3-dimensional space of a defined ellipsoid (or sphere), or of a Cartesian coordinate system centered in this ellipsoid (or sphere). 13.1.66 GeodeticDatumPropertyType gml:GeodeticDatumPropertyType is a property type for association roles to a geodetic datum, either referencing or containing the definition of that datum. 13.1.67 GeodeticDatumType 13.1.68 greenwichLongitude gml:greenwichLongitude is the longitude of the prime meridian measured from the Greenwich meridian, positive eastward. If the value of the prime meridian "name" is "Greenwich" then the value of greenwichLongitude shall be 0 degrees. 13.1.69 id The attribute gml:id supports provision of a handle for the XML element representing a GML Object. Its use is mandatory for all GML objects. It is of XML type ID, so is constrained to be unique in the XML document within which it occurs. 13.1.70 IdentifiedObjectType gml:IdentifiedObjectType provides identification properties of a CRS-related object. In gml:DefinitionType, the gml:identifier element shall be the primary name by which this object is identified, encoding the "name" attribute in the UML model. 13.1.71 identifier Often, a special identifier is assigned to an object by the maintaining authority with the intention that it is used in references to the object For such cases, the codeSpace shall be provided. That identifier is usually unique either globally or within an application domain. gml:identifier is a pre-defined property for such identifiers. 13.1.72 LengthType This is a prototypical definition for a specific measure type defined as a vacuous extension (i.e. aliases) of gml:MeasureType. In this case, the content model supports the description of a length (or distance) quantity, with its units. The unit of measure referenced by uom shall be suitable for a length, such as metres or feet. 13.1.73 maximumValue The gml:minimumValue and gml:maximumValue properties allow the specification of minimum and maximum value normally allowed for this axis, in the unit of measure for the axis. For a continuous angular axis such as longitude, the values wrap-around at this value. Also, values beyond this minimum/maximum can be used for specified purposes, such as in a bounding box. A value of minus infinity shall be allowed for the gml:minimumValue element, a value of plus infiniy for the gml:maximumValue element. If these elements are omitted, the value is unspecified. 13.1.74 MeasureType gml:MeasureType supports recording an amount encoded as a value of XML Schema double, together with a units of measure indicated by an attribute uom, short for "units Of measure". The value of the uom attribute identifies a reference system for the amount, usually a ratio or interval scale. 13.1.75 minimumValue The gml:minimumValue and gml:maximumValue properties allow the specification of minimum and maximum value normally allowed for this axis, in the unit of measure for the axis. For a continuous angular axis such as longitude, the values wrap-around at this value. Also, values beyond this minimum/maximum can be used for specified purposes, such as in a bounding box. A value of minus infinity shall be allowed for the gml:minimumValue element, a value of plus infiniy for the gml:maximumValue element. If these elements are omitted, the value is unspecified. 13.1.76 ModelGroup1 13.1.77 ModelGroup2 13.1.78 name The gml:name property provides a label or identifier for the object, commonly a descriptive name. An object may have several names, typically assigned by different authorities. gml:name uses the gml:CodeType content model. The authority for a name is indicated by the value of its (optional) codeSpace attribute. The name may or may not be unique, as determined by the rules of the organization responsible for the codeSpace. In common usage there will be one name per authority, so a processing application may select the name from its preferred codeSpace. 13.1.79 NilReasonType gml:NilReasonType defines a content model that allows recording of an explanation for a void value or other exception. 13.1.80 operationVersion gml:operationVersion is the version of the coordinate transformation (i.e., instantiation due to the stochastic nature of the parameters). Mandatory when describing a transformation, and should not be supplied for a conversion. 13.1.81 OwnershipAttributeGroup Encoding a GML property inline vs. by-reference shall not imply anything about the "ownership" of the contained or referenced GML Object, i.e. the encoding style shall not imply any "deep-copy" or "deep-delete" semantics. To express ownership over the contained or referenced GML Object, the gml:OwnershipAttributeGroup attribute group may be added to object-valued property elements. If the attribute group is not part of the content model of such a property element, then the value may not be "owned". 13.1.82 primeMeridian gml:primeMeridian is an association role to the prime meridian used by this geodetic datum. 13.1.83 PrimeMeridian A gml:PrimeMeridian defines the origin from which longitude values are determined. The default value for the prime meridian gml:identifier value is "Greenwich". 13.1.84 PrimeMeridianPropertyType gml:PrimeMeridianPropertyType is a property type for association roles to a prime meridian, either referencing or containing the definition of that meridian. 13.1.85 PrimeMeridianType 13.1.86 ProjectedCRS gml:ProjectedCRS is a 2D coordinate reference system used to approximate the shape of the earth on a planar surface, but in such a way that the distortion that is inherent to the approximation is carefully controlled and known. Distortion correction is commonly applied to calculated bearings and distances to produce values that are a close match to actual field values. 13.1.87 ProjectedCRSType 13.1.88 rangeMeaning gml:rangeMeaning describes the meaning of axis value range specified by gml:minimumValue and gml:maximumValue. This element shall be omitted when both gml:minimumValue and gml:maximumValue are omitted. This element should be included when gml:minimumValue and/or gml:maximumValue are included. If this element is omitted when the gml:minimumValue and/or gml:maximumValue are included, the meaning is unspecified. The codeSpace attribute shall reference a source of information specifying the values and meanings of all the allowed string values for this property. 13.1.89 realizationEpoch gml:realizationEpoch is the time after which this datum definition is valid. See ISO 19111 Table 32 for details. 13.1.90 ReferenceType gml:ReferenceType is intended to be used in application schemas directly, if a property element shall use a "by-reference only" encoding. 13.1.91 RelatedTimeType gml:RelatedTimeType provides a content model for indicating the relative position of an arbitrary member of the substitution group whose head is gml:AbstractTimePrimitive. It extends the generic gml:TimePrimitivePropertyType with an XML attribute relativePosition, whose value is selected from the set of 13 temporal relationships identified by Allen (1983) 13.1.92 remarks 13.1.93 scope The gml:scope property provides a description of the usage, or limitations of usage, for which this CRS-related object is valid. If unknown, enter "not known". 13.1.94 secondDefiningParameter 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. 13.1.95 SecondDefiningParameter 13.1.96 semiMajorAxis gml:semiMajorAxis specifies the length of the semi-major axis of the ellipsoid, with its units. Uses the MeasureType with the restriction that the unit of measure referenced by uom must be suitable for a length, such as metres or feet. 13.1.97 SimpleTypeClass1 13.1.98 sourceCRS gml:sourceCRS is an association role to the source CRS (coordinate reference system) of this coordinate operation. 13.1.99 sphericalCS gml:sphericalCS is an association role to the spherical coordinate system used by this CRS. 13.1.100 SphericalCS gml:SphericalCS is a three-dimensional coordinate system with one distance measured from the origin and two angular coordinates. A SphericalCS shall have three gml:axis property elements. 13.1.101 SphericalCSPropertyType gml:SphericalCSPropertyType is property type for association roles to a spherical coordinate system, either referencing or containing the definition of that coordinate system. 13.1.102 SphericalCSType 13.1.103 StandardObjectProperties 13.1.104 string 13.1.105 StringOrRefType 13.1.106 targetCRS gml:targetCRS is an association role to the target CRS (coordinate reference system) of this coordinate operation. 13.1.107 TimePrimitivePropertyType gml:TimePrimitivePropertyType provides a standard content model for associations between an arbitrary member of the substitution group whose head is gml:AbstractTimePrimitive and another object. 13.1.108 UomIdentifier The simple type gml:UomIdentifer defines the syntax and value space of the unit of measure identifier. 13.1.109 UomSymbol This type specifies a character string of length at least one, and restricted such that it must not contain any of the following characters: ":" (colon), " " (space), (newline), (carriage return), (tab). This allows values corresponding to familiar abbreviations, such as "kg", "m/s", etc. 13.1.110 UomURI This type specifies a URI, restricted such that it must start with one of the following sequences: "#", "./", "../", or a string of characters followed by a ":". These patterns ensure that the most common URI forms are supported, including absolute and relative URIs and URIs that are simple fragment identifiers, but prohibits certain forms of relative URI that could be mistaken for unit of measure symbol . 13.1.111 VerticalCRS gml:VerticalCRS is a 1D coordinate reference system used for recording heights or depths. Vertical CRSs make use of the direction of gravity to define the concept of height or depth, but the relationship with gravity may not be straightforward. By implication, ellipsoidal heights (h) cannot be captured in a vertical coordinate reference system. Ellipsoidal heights cannot exist independently, but only as an inseparable part of a 3D coordinate tuple defined in a geographic 3D coordinate reference system. 13.1.112 VerticalCRSType 13.1.113 VerticalCS gml:VerticalCS is a one-dimensional coordinate system used to record the heights or depths of points. Such a coordinate system is usually dependent on the Earth's gravity field, perhaps loosely as when atmospheric pressure is the basis for the vertical coordinate system axis. A VerticalCS shall have one gml:axis property element. 13.1.114 verticalCS gml:verticalCS is an association role to the vertical coordinate system used by this CRS. 13.1.115 VerticalCSPropertyType gml:VerticalCSPropertyType is a property type for association roles to a vertical coordinate system, either referencing or containing the definition of that coordinate system. 13.1.116 VerticalCSType 13.1.117 VerticalDatum gml:VerticalDatum is a textual description and/or a set of parameters identifying a particular reference level surface used as a zero-height surface, including its position with respect to the Earth for any of the height types recognized by this International Standard. 13.1.118 verticalDatum gml:verticalDatum is an association role to the vertical datum used by this CRS. 13.1.119 VerticalDatumPropertyType gml:VerticalDatumPropertyType is property type for association roles to a vertical datum, either referencing or containing the definition of that datum. 13.1.120 VerticalDatumType