Package org.apache.sis.referencing.datum

Class DefaultEllipsoid

  • All Implemented Interfaces:
    Serializable, Deprecable, Lenient­Comparable, Ellipsoid, Identified­Object
    public class DefaultEllipsoid
extends AbstractIdentifiedObject
implements Ellipsoid
    Geometric figure that can 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. An ellipsoid requires two defining parameters: Some numerical values derived from the above properties are:
    Creating new ellipsoid 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 database provides definitions for many ellipsoids, 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 an ellipsoid. The other choices provide more freedom. Each choice delegates its work to the subsequent items (in the default configuration), so this list can been seen as top to bottom API.

    1. Create an Ellipsoid from one of the static convenience shortcuts listed in Common­CRS​.ellipsoid().
    2. Create an Ellipsoid from an identifier in a database by invoking Datum­Authority­Factory​.create­Ellipsoid(String).
    3. Create an Ellipsoid by invoking the Datum­Factory​.create­Ellipsoid(…) or create­Flattened­Sphere(…) method (implemented for example by Geodetic­Object­Factory).
    4. Create a Default­Ellipsoid by invoking the create­Ellipsoid(…) or create­Flattened­Sphere(…) static methods defined in this class.
    Example: the following code gets the WGS84 ellipsoid: 
    Ellipsoid e = CommonCRS.WGS84.ellipsoid();
    Immutability and thread safety
    This class is immutable and thus thread-safe if the property values (not necessarily the map itself) given to the constructors 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
    See Also:
    Common­CRS​.ellipsoid(), Geodetic­Authority­Factory​.create­Ellipsoid(String), Serialized Form

    Defined in the sis-referencing module

    • Method Detail

      • createEllipsoid

        public static DefaultEllipsoid createEllipsoid​(Map<String,​?> properties,
                                               double semiMajorAxis,
                                               double semiMinorAxis,
                                               Unit<Length> unit)
        Creates a new ellipsoid using the specified properties and axis length. The properties map is given unchanged to the super-class constructor.
        Parameters:
        properties - the properties to be given to the identified object.
        semi­Major­Axis - the equatorial radius in the given unit.
        semi­Minor­Axis - the polar radius in the given unit.
        unit - the units of the semi-major and semi-minor axis values.
        Returns:
        an ellipsoid with the given axis length.
        See Also:
        Geodetic­Object­Factory​.create­Ellipsoid(Map, double, double, Unit)

      • createFlattenedSphere

        public static DefaultEllipsoid createFlattenedSphere​(Map<String,​?> properties,
                                                     double semiMajorAxis,
                                                     double inverseFlattening,
                                                     Unit<Length> unit)
        Creates a new ellipsoid using the specified properties, axis length and inverse flattening value. The properties map is given unchanged to the super-class constructor.
        Parameters:
        properties - the properties to be given to the identified object.
        semi­Major­Axis - the equatorial radius in the given unit.
        inverse­Flattening - the inverse flattening value.
        unit - the units of the semi-major and semi-minor axis values.
        Returns:
        an ellipsoid with the given axis length.
        See Also:
        Geodetic­Object­Factory​.create­Flattened­Sphere(Map, double, double, Unit)

      • castOrCopy

        public static DefaultEllipsoid castOrCopy​(Ellipsoid object)
        Returns a SIS ellipsoid 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 Ellipsoid> getInterface()
        Returns the GeoAPI interface implemented by this class. The SIS implementation returns Ellipsoid​.class.
        Note for implementers: Subclasses usually do not need to override this method since GeoAPI does not define Ellipsoid 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:
        Ellipsoid​.class or a user-defined sub-interface.

      • getSemiMajorAxis

        public double getSemiMajorAxis()
        Length of the semi-major axis of the ellipsoid. This is the equatorial radius in axis linear unit.
        Specified by:
        get­Semi­Major­Axis in interface Ellipsoid
        Returns:
        length of semi-major axis.

      • getSemiMinorAxis

        public double getSemiMinorAxis()
        Length of the semi-minor axis of the ellipsoid. This is the polar radius in axis linear unit.
        Specified by:
        get­Semi­Minor­Axis in interface Ellipsoid
        Returns:
        length of semi-minor axis.

      • getAuthalicRadius

        public double getAuthalicRadius()
        Returns the radius of a hypothetical sphere having the same surface than this ellipsoid. The radius is expressed in axis linear unit.
        Returns:
        the radius of a sphere having the same surface than this ellipsoid.
        See Also:
        Common­CRS​.SPHERE

      • getEccentricity

        public double getEccentricity()
        The ratio of the distance between the center and a focus of the ellipse to the length of its semi-major axis. The eccentricity can alternately be computed from the equation: ℯ = √(2f - f²) where f is the flattening factor (not inverse).
        Returns:
        ℯ, the eccentricity of this ellipsoid.

      • getEccentricitySquared

        public double getEccentricitySquared()
        Returns the square of the eccentricity value.
        Purpose: this convenience method is provided because ℯ² is frequently used in coordinate operations, actually more often than ℯ. This convenience method avoids the cost of computing the square root when not needed.
        Returns:
        ℯ², the square of the eccentricity value.
        Since:
        0.7

      • getInverseFlattening

        public double getInverseFlattening()
        Returns the value of the inverse of the flattening constant. Flattening is a value used to indicate how closely an ellipsoid approaches a spherical shape. The inverse flattening is related to the equatorial/polar radius by the formula:
        ivf = re / (re - rp).
        For perfect spheres (i.e. if is­Sphere() returns true), the Double​.POSITIVE_INFINITY value is used.
        Specified by:
        get­Inverse­Flattening in interface Ellipsoid
        Returns:
        the inverse flattening value.

      • isIvfDefinitive

        public boolean isIvfDefinitive()
        Indicates if the inverse flattening is definitive for this ellipsoid. Some ellipsoids use the IVF as the defining value, and calculate the polar radius whenever asked. Other ellipsoids use the polar radius to calculate the IVF whenever asked. This distinction can be important to avoid floating-point rounding errors.
        Specified by:
        is­Ivf­Definitive in interface Ellipsoid
        Returns:
        true if the inverse flattening is definitive, or false if the polar radius is definitive.

      • isSphere

        public boolean isSphere()
        true if the ellipsoid is degenerate and is actually a sphere. The sphere is completely defined by the semi-major axis, which is the radius of the sphere.
        Specified by:
        is­Sphere in interface Ellipsoid
        Returns:
        true if the ellipsoid is degenerate and is actually a sphere.

      • orthodromicDistance

        @Deprecated
public double orthodromicDistance​(double λ1,
                                  double φ1,
                                  double λ2,
                                  double φ2)
        Deprecated.
        Replaced by Geodetic­Calculator.
        Returns the orthodromic distance between two geographic coordinates. The orthodromic distance is the shortest distance between two points on a ellipsoid's surface. The orthodromic path is always on a great circle.
        Note: Orthodromic distances are different than the loxodromic distance. The later is a longer distance on a path with a constant direction on the compass.
        Parameters:
        \u03bb1 - longitude of first point (in decimal degrees).
        \u03c61 - latitude of first point (in decimal degrees).
        \u03bb2 - longitude of second point (in decimal degrees).
        \u03c62 - latitude of second point (in decimal degrees).
        Returns:
        the orthodromic distance (in the units of this ellipsoid's axis).
        See Also:
        SIS-386

      • semiMajorAxisDifference

        public double semiMajorAxisDifference​(Ellipsoid other)
        Returns the difference between the semi-major axis length of two ellipsoids. If the two ellipsoid does not use the same unit of measurement, than the axis length of the other ellipsoid is converted into the units of this ellipsoid axis.
        Example: WGS84​.semi­Major­Axis­Difference(ED50) returns 251 metres. This information is a parameter of Molodensky transformations.
        Parameters:
        other - the other ellipsoid from which to get semi-major axis length difference.
        Returns:
        (other ellipsoid semi-major axis) - (this ellipsoid semi-major axis).
        Since:
        0.7

      • flatteningDifference

        public double flatteningDifference​(Ellipsoid other)
        Returns the difference between the flattening factor of two ellipsoids. This method returns 0 if the two ellipsoids are equal.
        Example: WGS84​.flattening­Difference(ED50) returns approximately 1.41927E-05. This information is a parameter of Molodensky transformations.
        Parameters:
        other - the other ellipsoid from which to get flattening difference.
        Returns:
        (other ellipsoid flattening) - (this ellipsoid flattening).
        Since:
        0.7