org.opengis.referencing.datum
Interface Datum

All Superinterfaces:

Info

All Known Subinterfaces:

EngineeringDatum, GeodeticDatum, ImageDatum, TemporalDatum, VerticalDatum

public interface Datum

extends Info

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.

Version:

Abstract specification 2.0

Author:

ISO 19111, OpenGIS® consortium

See Also:

CoordinateSystem, CoordinateReferenceSystem

UML identifier (abstract type): CD_Datum

Method Summary

String	getAnchorPoint(Locale locale) Description, possibly including coordinates, of the point or points used to anchor the datum to the Earth.
Date	getRealizationEpoch() The time after which this datum definition is valid.
String	getScope(Locale locale) Description of domain of usage, or limitations of usage, for which this datum object is valid.
Extent	getValidArea() Area or region in which this datum object is valid.

Methods inherited from interface Info

getIdentifiers, getName, getRemarks

Method Detail

getAnchorPoint

String getAnchorPoint(Locale locale)

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.

Parameters:

locale - The desired locale for the datum anchor point to be returned, or null for anchor point in some default locale (may or may not be the system default).

Returns:

The datum anchor point in the given locale, or null if none. If no anchor point is available in the given locale, then some default locale is used.

UML identifier (optional attribute): anchorPoint

getRealizationEpoch

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.

Returns:

The datum realization epoch, or null if not available.

UML identifier (optional attribute): realizationEpoch

getValidArea

Extent getValidArea()

Area or region in which this datum object is valid.

Returns:

The datum valid area, or null if not available.

UML identifier (optional attribute): validArea

getScope

String getScope(Locale locale)

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

Parameters:

locale - The desired locale for the datum scope to be returned, or null for scope in some default locale (may or may not be the system default).

Returns:

The datum scope in the given locale, or null if none. If no scope is available in the given locale, then some default locale is used.

UML identifier (optional attribute): scope