Class DefaultPrimeMeridian

All Implemented Interfaces:
Serializable, Formattable, Deprecable, LenientComparable, org.opengis.referencing.datum.PrimeMeridian, org.opengis.referencing.IdentifiedObject

public class DefaultPrimeMeridian extends AbstractIdentifiedObject implements org.opengis.referencing.datum.PrimeMeridian
Defines the origin from which longitude values are determined.

Creating new prime meridian instances

New instances can be created either directly by specifying all information to a factory method (choices 3 and 4 below), or indirectly by specifying the identifier of an entry in a database (choices 1 and 2 below). In particular, the EPSG repository provides definitions for many prime meridians, and Apache SIS provides convenience shortcuts for some of them.

Choice 1 in the following list is the easiest but most restrictive way to get a prime meridian. The other choices provide more freedom. Each choice delegates its work to the subsequent items (in the default configuration), so this list can be seen as top to bottom API.

  1. Create a PrimeMeridian from one of the static convenience shortcuts listed in CommonCRS.primeMeridian().
  2. Create a PrimeMeridian from an identifier in a database by invoking DatumAuthorityFactory.createPrimeMeridian(String).
  3. Create a PrimeMeridian by invoking the DatumFactory.createPrimeMeridian(…) method (implemented for example by GeodeticObjectFactory).
  4. Create a DefaultPrimeMeridian by invoking the constructor.
Example: the following code gets the Greenwich prime meridian:

Immutability and thread safety

This class is immutable and thus thread-safe if the property values (not necessarily the map itself) given to the constructor are also immutable. Unless otherwise noted in the javadoc, this condition holds if all components were created using only SIS factories and static constants.
Since:
0.4
Version:
0.7
See Also:
  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    private javax.measure.Unit<javax.measure.quantity.Angle>
    The angular unit of the Greenwich longitude.
    private double
    Longitude of the prime meridian measured from the Greenwich meridian, positive eastward.
    private static final long
    Serial number for inter-operability with different versions.

    Fields inherited from class org.apache.sis.referencing.AbstractIdentifiedObject

    DEPRECATED_KEY, LOCALE_KEY

    Fields inherited from interface org.opengis.referencing.IdentifiedObject

    ALIAS_KEY, IDENTIFIERS_KEY, NAME_KEY, REMARKS_KEY
  • Constructor Summary

    Constructors
    Modifier
    Constructor
    Description
    private
    Constructs a new object in which every attributes are set to a null value.
     
    DefaultPrimeMeridian(Map<String,?> properties, double greenwichLongitude, javax.measure.Unit<javax.measure.quantity.Angle> angularUnit)
    Creates a prime meridian from the given properties.
    protected
    DefaultPrimeMeridian(org.opengis.referencing.datum.PrimeMeridian meridian)
    Creates a new prime meridian with the same values than the specified one.
  • Method Summary

    Modifier and Type
    Method
    Description
    private static boolean
    beConservative(Formatter formatter, javax.measure.Unit<javax.measure.quantity.Angle> contextualUnit)
    Returns true if formatTo(Formatter) should conservatively format the angular unit even if it would be legal to omit it.
    castOrCopy(org.opengis.referencing.datum.PrimeMeridian object)
    Returns a SIS prime meridian implementation with the same values than the given arbitrary implementation.
    protected long
    Invoked by hashCode() for computing the hash code when first needed.
    boolean
    equals(Object object, ComparisonMode mode)
    Compares this prime meridian with the specified object for equality.
    protected String
    formatTo(Formatter formatter)
    Formats this prime meridian as a Well Known Text PrimeMeridian[…] element.
    javax.measure.Unit<javax.measure.quantity.Angle>
    Returns the angular unit of the Greenwich longitude.
    double
    Longitude of the prime meridian measured from the Greenwich meridian, positive eastward.
    double
    getGreenwichLongitude(javax.measure.Unit<javax.measure.quantity.Angle> unit)
    Returns the longitude value relative to the Greenwich Meridian, expressed in the specified units.
    private Measure
    Invoked by JAXB for obtaining the Greenwich longitude to marshal together with its "uom" attribute.
    Class<? extends org.opengis.referencing.datum.PrimeMeridian>
    Returns the GeoAPI interface implemented by this class.
    private static boolean
    Returns true if the given formatter is in the process of formatting the prime meridian of a base CRS of an AbstractDerivedCRS.
    private void
    Invoked by JAXB for setting the Greenwich longitude and its unit of measurement.

    Methods inherited from class org.apache.sis.io.wkt.FormattableObject

    print, toString, toString, toWKT

    Methods inherited from class java.lang.Object

    clone, finalize, getClass, notify, notifyAll, wait, wait, wait

    Methods inherited from interface org.opengis.referencing.IdentifiedObject

    getAlias, getIdentifiers, getName, getRemarks, toWKT
  • Field Details

    • serialVersionUID

      private static final long serialVersionUID
      Serial number for inter-operability with different versions.
      See Also:
    • greenwichLongitude

      private double greenwichLongitude
      Longitude of the prime meridian measured from the Greenwich meridian, positive eastward.

      Consider this field as final! This field is modified only at unmarshalling time by setGreenwichMeasure(Measure)

    • angularUnit

      private javax.measure.Unit<javax.measure.quantity.Angle> angularUnit
      The angular unit of the Greenwich longitude.

      Consider this field as final! This field is modified only at unmarshalling time by setGreenwichMeasure(Measure)

  • Constructor Details

    • DefaultPrimeMeridian

      public DefaultPrimeMeridian(Map<String,?> properties, double greenwichLongitude, javax.measure.Unit<javax.measure.quantity.Angle> angularUnit)
      Creates a prime meridian from the given properties. The properties map is given unchanged to the super-class constructor. The following table is a reminder of main (not all) properties:
      Recognized properties (non exhaustive list)
      Property name Value type Returned by
      "name" ReferenceIdentifier or String AbstractIdentifiedObject.getName()
      "alias" GenericName or CharSequence (optionally as array) AbstractIdentifiedObject.getAlias()
      "identifiers" ReferenceIdentifier (optionally as array) AbstractIdentifiedObject.getIdentifiers()
      "remarks" InternationalString or String AbstractIdentifiedObject.getRemarks()
      Parameters:
      properties - the properties to be given to the identified object.
      greenwichLongitude - the longitude value relative to the Greenwich Meridian.
      angularUnit - the angular unit of the longitude.
      See Also:
    • DefaultPrimeMeridian

      protected DefaultPrimeMeridian(org.opengis.referencing.datum.PrimeMeridian meridian)
      Creates a new prime meridian with the same values than the specified one. This copy constructor provides a way to convert an arbitrary implementation into a SIS one or a user-defined one (as a subclass), usually in order to leverage some implementation-specific API.

      This constructor performs a shallow copy, i.e. the properties are not cloned.

      Parameters:
      meridian - the prime meridian to copy.
      See Also:
    • DefaultPrimeMeridian

      private DefaultPrimeMeridian()
      Constructs a new object in which every attributes are set to a null value. This is not a valid object. This constructor is strictly reserved to JAXB, which will assign values to the fields using reflection.
  • Method Details

    • castOrCopy

      public static DefaultPrimeMeridian castOrCopy(org.opengis.referencing.datum.PrimeMeridian object)
      Returns a SIS prime meridian implementation with the same values than the given arbitrary implementation. If the given object is null, then this method returns null. Otherwise if the given object is already a SIS implementation, then the given object is returned unchanged. Otherwise a new SIS implementation is created and initialized to the attribute values of the given object.
      Parameters:
      object - the object to get as a SIS implementation, or null if none.
      Returns:
      a SIS implementation containing the values of the given object (may be the given object itself), or null if the argument was null.
    • getInterface

      public Class<? extends org.opengis.referencing.datum.PrimeMeridian> getInterface()
      Returns the GeoAPI interface implemented by this class. The SIS implementation returns PrimeMeridian.class.
      Note for implementers: Subclasses usually do not need to override this method since GeoAPI does not define PrimeMeridian sub-interface. Overriding possibility is left mostly for implementers who wish to extend GeoAPI with their own set of interfaces.
      Overrides:
      getInterface in class AbstractIdentifiedObject
      Returns:
      PrimeMeridian.class or a user-defined sub-interface.
    • getGreenwichLongitude

      public double getGreenwichLongitude()
      Longitude of the prime meridian measured from the Greenwich meridian, positive eastward.
      Specified by:
      getGreenwichLongitude in interface org.opengis.referencing.datum.PrimeMeridian
      Returns:
      the prime meridian Greenwich longitude, in angular unit.
    • getGreenwichLongitude

      public double getGreenwichLongitude(javax.measure.Unit<javax.measure.quantity.Angle> unit)
      Returns the longitude value relative to the Greenwich Meridian, expressed in the specified units. This convenience method makes it easier to obtain longitude in decimal degrees using the following code, regardless of the underlying angular units of this prime meridian:
      Parameters:
      unit - the unit in which to express longitude.
      Returns:
      the Greenwich longitude in the given units.
    • getAngularUnit

      public javax.measure.Unit<javax.measure.quantity.Angle> getAngularUnit()
      Returns the angular unit of the Greenwich longitude.
      Specified by:
      getAngularUnit in interface org.opengis.referencing.datum.PrimeMeridian
      Returns:
      the angular unit of the Greenwich longitude.
    • equals

      public boolean equals(Object object, ComparisonMode mode)
      Compares this prime meridian with the specified object for equality.
      Specified by:
      equals in interface LenientComparable
      Overrides:
      equals in class AbstractIdentifiedObject
      Parameters:
      object - the object to compare to this.
      mode - STRICT for performing a strict comparison, or IGNORE_METADATA for comparing only properties relevant to coordinate transformations.
      Returns:
      true if both objects are equal.
      See Also:
    • computeHashCode

      protected long computeHashCode()
      Invoked by hashCode() for computing the hash code when first needed. See AbstractIdentifiedObject.computeHashCode() for more information.
      Overrides:
      computeHashCode in class AbstractIdentifiedObject
      Returns:
      the hash code value. This value may change in any future Apache SIS version.
    • isElementOfBaseCRS

      private static boolean isElementOfBaseCRS(Formatter formatter)
      Returns true if the given formatter is in the process of formatting the prime meridian of a base CRS of an AbstractDerivedCRS. In such case, base CRS coordinate system axes shall not be formatted, which has the consequence of bringing the UNIT[…] element right below the PRIMEM[…] one. Example: If we were not formatting a base CRS, we would have many lines between PrimeMeridian[…] and AngleUnit[…] in the above example, which would make less obvious that the angle unit applies also to the prime meridian. It does not bring any ambiguity from an ISO 19162 standard point of view, but historically some other software products interpreted the PRIMEM[…] units wrongly, which is why we try to find a compromise between keeping the WKT simple and avoiding an historical ambiguity.
      See Also:
    • beConservative

      private static boolean beConservative(Formatter formatter, javax.measure.Unit<javax.measure.quantity.Angle> contextualUnit)
      Returns true if formatTo(Formatter) should conservatively format the angular unit even if it would be legal to omit it.

      Rational

      According the ISO 19162 standard, it is legal to omit the PrimeMeridian angular unit when that unit is the same than the unit of the axes of the enclosing GeographicCRS. However, the relationship between the CRS axes and the prime meridian is less obvious in WKT2 than it was in WKT1, because the WKT2 UNIT[…] element is far from the PRIMEM[…] element while it was just below it in WKT1. Furthermore, the PRIMEM[…] unit is one source of incompatibility between various WKT1 parsers (i.e. some popular libraries are not conform to OGC 01-009 and ISO 19162). So we are safer to unconditionally format any unit other than degrees, even if we could legally omit them.

      However, in order to keep the WKT slightly simpler in Convention.WKT2_SIMPLIFIED mode, we make an exception to the above-cited safety if the UNIT[…] element is formatted right below the PRIMEM[…] one, which happen if we are inside a base CRS. See isElementOfBaseCRS(Formatter) for more discussion.

    • formatTo

      protected String formatTo(Formatter formatter)
      Formats this prime meridian as a Well Known Text PrimeMeridian[…] element.
      Overrides:
      formatTo in class AbstractIdentifiedObject
      Parameters:
      formatter - the formatter where to format the inner content of this WKT element.
      Returns:
      "PrimeMeridian" (WKT 2) or "PrimeM" (WKT 1).
      See Also:
    • getGreenwichMeasure

      private Measure getGreenwichMeasure()
      Invoked by JAXB for obtaining the Greenwich longitude to marshal together with its "uom" attribute.
    • setGreenwichMeasure

      private void setGreenwichMeasure(Measure measure)
      Invoked by JAXB for setting the Greenwich longitude and its unit of measurement.