Package org.geotools.referencing.datum

Class AbstractDatum

  • All Implemented Interfaces:
    Serializable, Datum, IdentifiedObject
    Direct Known Subclasses:
    DefaultEngineeringDatum, DefaultGeodeticDatum, DefaultImageDatum, DefaultTemporalDatum, DefaultVerticalDatum
    public class AbstractDatum
extends AbstractIdentifiedObject
implements Datum
    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.

    A datum can be defined as a set of real points on the earth that have coordinates. The definition of the datum may also include the temporal behavior (such as the rate of change of the orientation of the coordinate axes).

    This class is conceptually abstract, even if it is technically possible to instantiate it. Typical applications should create instances of the most specific subclass with Default prefix instead. An exception to this rule may occurs when it is not possible to identify the exact type.

    Since:
    2.1
    Author:
    Martin Desruisseaux (IRD)
    See Also:
    AbstractCS, AbstractCRS, Serialized Form

    • Method Detail

      • getAnchorPoint

        public 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.
        Specified by:
        getAnchorPoint in interface Datum
        Returns:
        A description of the anchor point, or null if none.

      • getRealizationEpoch

        public 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.
        Specified by:
        getRealizationEpoch in interface Datum
        Returns:
        The datum realization epoch, or null if not available.

      • getDomainOfValidity

        public Extent getDomainOfValidity()
        Area or region or timeframe in which this datum is valid.
        Specified by:
        getDomainOfValidity in interface Datum
        Returns:
        The datum valid domain, or null if not available.
        Since:
        2.4

      • getScope

        public InternationalString getScope()
        Description of domain of usage, or limitations of usage, for which this datum object is valid.
        Specified by:
        getScope in interface Datum
        Returns:
        A description of domain of usage, or null if none.

      • equals

        public boolean equals​(AbstractIdentifiedObject object,
                      boolean compareMetadata)
        Compares the specified object with this datum for equality.
        Overrides:
        equals in class AbstractIdentifiedObject
        Parameters:
        object - The object to compare to this.
        compareMetadata - true for performing a strict comparaison, or false for comparing only properties relevant to transformations.
        Returns:
        true if both objects are equal.