org.opengis.referencing.datum

Interface Datum

All Superinterfaces:

IdentifiedObject

All Known Subinterfaces:

EngineeringDatum, GeodeticDatum, ImageDatum, TemporalDatum, VerticalDatum

@UML(identifier="CD_Datum",
     specification=ISO_19111)
public interface Datum
extends IdentifiedObject

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 can be associated with only specific types of coordinate systems.

Since:

1.0

See Also:

CoordinateSystem, CoordinateReferenceSystem

Field Summary

Fields

Modifier and Type	Field and Description
static String	ANCHOR_POINT_KEY Key for the "anchorPoint" property to be given to the datum factory createFoo(…) methods.
static String	DOMAIN_OF_VALIDITY_KEY Key for the "domainOfValidity" property to be given to the datum factory createFoo(…) methods.
static String	REALIZATION_EPOCH_KEY Key for the "realizationEpoch" property to be given to the datum factory createFoo(…) methods.
static String	SCOPE_KEY Key for the "scope" property to be given to the datum factory createFoo(…) methods.

Fields inherited from interface IdentifiedObject

ALIAS_KEY, IDENTIFIERS_KEY, NAME_KEY, REMARKS_KEY

Method Summary

Modifier and Type	Method and Description
InternationalString	getAnchorPoint() Description, possibly including coordinates, of the point or points used to anchor the datum to the Earth.
Extent	getDomainOfValidity() Area or region or timeframe in which this datum is valid.
Date	getRealizationEpoch() The time after which this datum definition is valid.
InternationalString	getScope() Description of domain of usage, or limitations of usage, for which this datum object is valid.

Methods inherited from interface IdentifiedObject

getAlias, getIdentifiers, getName, getRemarks, toWKT

Field Detail

ANCHOR_POINT_KEY

static final String ANCHOR_POINT_KEY

Key for the "anchorPoint" property to be given to the datum factory createFoo(…) methods. This is used for setting the value to be returned by getAnchorPoint().

See Also:

getAnchorPoint(), Constant Field Values

REALIZATION_EPOCH_KEY

static final String REALIZATION_EPOCH_KEY

Key for the "realizationEpoch" property to be given to the datum factory createFoo(…) methods. This is used for setting the value to be returned by getRealizationEpoch().

See Also:

getRealizationEpoch(), Constant Field Values

DOMAIN_OF_VALIDITY_KEY

static final String DOMAIN_OF_VALIDITY_KEY

Key for the "domainOfValidity" property to be given to the datum factory createFoo(…) methods. This is used for setting the value to be returned by getDomainOfValidity().

Since:

2.1

See Also:

getDomainOfValidity(), Constant Field Values

SCOPE_KEY

static final String SCOPE_KEY

Key for the "scope" property to be given to the datum factory createFoo(…) methods. This is used for setting the value to be returned by getScope().

See Also:

getScope(), Constant Field Values

Method Detail

getAnchorPoint

@UML(identifier="anchorPoint",
     obligation=OPTIONAL,
     specification=ISO_19111)
InternationalString getAnchorPoint()

Description, possibly including coordinates, of the point or points used to anchor the datum to the Earth. Also known as the "origin", especially for Engineering and Image Datums.

• For a geodetic datum, this point is also known as the fundamental point, which is traditionally the point where the relationship between geoid and ellipsoid is defined. In some cases, the "fundamental point" may consist of a number of points. In those cases, the parameters defining the geoid/ellipsoid relationship have then been averaged for these points, and the averages adopted as the datum definition.
• For an engineering datum, the anchor point may be a physical point, or it may be a point with defined coordinates in another CRS.
• For an image datum, the anchor point is usually either the centre of the image or the corner of the image.
• For a temporal datum, this attribute is not defined. Instead of the anchor point, a temporal datum carries a separate time origin of type Date.

Returns:

A description of the anchor point, or null if none.

getRealizationEpoch

@UML(identifier="realizationEpoch",
     obligation=OPTIONAL,
     specification=ISO_19111)
Date getRealizationEpoch()

The time after which this datum definition is valid. This time may be precise (e.g. 1997 for IRTF97) or merely a year (e.g. 1983 for NAD83). In the latter case, the epoch usually refers to the year in which a major recalculation of the geodetic control network, underlying the datum, was executed or initiated. An old datum can remain valid after a new datum is defined. Alternatively, a datum may be superseded by a later datum, in which case the realization epoch for the new datum defines the upper limit for the validity of the superseded datum.

Warning: The return type of this method may change in GeoAPI 3.1 release. It may be replaced by a type matching more closely either ISO 19108 (Temporal Schema) or ISO 19103.

Returns:

The datum realization epoch, or null if not available.

getDomainOfValidity

@UML(identifier="domainOfValidity",
     obligation=OPTIONAL,
     specification=ISO_19111)
Extent getDomainOfValidity()

Area or region or timeframe in which this datum is valid.

Returns:

The datum valid domain, or null if not available.

Since:

2.1

getScope

@UML(identifier="scope",
     obligation=OPTIONAL,
     specification=ISO_19111)
InternationalString getScope()

Description of domain of usage, or limitations of usage, for which this datum object is valid.

Returns:

A description of domain of usage, or null if none.

Departure from OGC/ISO specification:
This method has been kept conformant with the specification published in 2003. The revision published in 2007 replaced the singleton by a collection and changed the obligation from "optional" to "mandatory", requiring a return value of "not known" if the scope is unknown. This change is still under review.