Package org.geotools.referencing.datum

Class DefaultEllipsoid

Object

Formattable

AbstractIdentifiedObject

DefaultEllipsoid

All Implemented Interfaces:

Serializable, Ellipsoid, IdentifiedObject, PROJFormattable

public class DefaultEllipsoid
extends AbstractIdentifiedObject
implements Ellipsoid, PROJFormattable

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:

• semi-major axis and inverse flattening, or
• semi-major axis and semi-minor axis.

Since:

2.1

Author:

Martin Desruisseaux (IRD)

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field	Description
static DefaultEllipsoid	CLARKE_1866	Clarke 1866 ellipsoid with axis in metres.
static DefaultEllipsoid	GRS80	GRS 80 ellipsoid with axis in metres.
static DefaultEllipsoid	INTERNATIONAL_1924	International 1924 ellipsoid with axis in metres.
static DefaultEllipsoid	SPHERE	A sphere with a radius of 6371000 metres.
static DefaultEllipsoid	WGS84	WGS 1984 ellipsoid with axis in metres.

Fields inherited from class AbstractIdentifiedObject

EMPTY_ALIAS_ARRAY, EMPTY_IDENTIFIER_ARRAY, IDENTIFIER_COMPARATOR, NAME_COMPARATOR, REMARKS_COMPARATOR

Fields inherited from class Formattable

SINGLE_LINE

Fields inherited from interface IdentifiedObject

ALIAS_KEY, IDENTIFIERS_KEY, NAME_KEY, REMARKS_KEY

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	DefaultEllipsoid(Map<String,?> properties, double semiMajorAxis, double semiMinorAxis, double inverseFlattening, boolean ivfDefinitive, Unit<Length> unit)	Constructs a new ellipsoid using the specified axis length.
protected	DefaultEllipsoid(Ellipsoid ellipsoid)	Constructs a new ellipsoid with the same values than the specified one.

Method Summary

Modifier and Type	Method	Description
static DefaultEllipsoid	createEllipsoid(String name, double semiMajorAxis, double semiMinorAxis, Unit<Length> unit)	Constructs a new ellipsoid using the specified axis length.
static DefaultEllipsoid	createEllipsoid(Map<String,?> properties, double semiMajorAxis, double semiMinorAxis, Unit<Length> unit)	Constructs a new ellipsoid using the specified axis length.
static DefaultEllipsoid	createFlattenedSphere(String name, double semiMajorAxis, double inverseFlattening, Unit<Length> unit)	Constructs a new ellipsoid using the specified axis length and inverse flattening value.
static DefaultEllipsoid	createFlattenedSphere(Map<String,?> properties, double semiMajorAxis, double inverseFlattening, Unit<Length> unit)	Constructs a new ellipsoid using the specified axis length and inverse flattening value.
boolean	equals(AbstractIdentifiedObject object, boolean compareMetadata)	Compare this ellipsoid with the specified object for equality.
String	formatPROJ(PROJFormatter formatter)	Format the inner part of a PROJFormattable object.
protected String	formatWKT(Formatter formatter)	Format the inner part of a Well Known Text (WKT) element.
Unit<Length>	getAxisUnit()	Returns the linear unit of the semi-major and semi-minor axis values.
double	getEccentricity()	The ratio of the distance between the center and a focus of the ellipse to the length of its semimajor axis.
double	getInverseFlattening()	Returns the value of the inverse of the flattening constant.
double	getSemiMajorAxis()	Length of the semi-major axis of the ellipsoid.
double	getSemiMinorAxis()	Length of the semi-minor axis of the ellipsoid.
int	hashCode()	Returns a hash value for this ellipsoid.
boolean	isIvfDefinitive()	Indicates if the inverse flattening is definitive for this ellipsoid.
boolean	isSphere()	true if the ellipsoid is degenerate and is actually a sphere.
double	orthodromicDistance(double x1, double y1, double x2, double y2)	Returns the orthodromic distance between two geographic coordinates.
double	orthodromicDistance(Point2D P1, Point2D P2)	Returns the orthodromic distance between two geographic coordinates.
static DefaultEllipsoid	wrap(Ellipsoid ellipsoid)	Wraps an arbitrary ellipsoid into a Geotools implementation.

Methods inherited from class AbstractIdentifiedObject

asSet, ensureAngularUnit, ensureLinearUnit, ensureNonNull, ensureNonNull, ensureTimeUnit, equals, equals, equals, equals, getAlias, getIdentifier, getIdentifier, getIdentifiers, getName, getName, getName, getProperties, getProperties, getRemarks, nameMatches, nameMatches, nameMatches

Methods inherited from class Formattable

cleanupThreadLocals, toString, toWKT, toWKT, toWKT, toWKT

Methods inherited from class Object

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

Methods inherited from interface IdentifiedObject

getAlias, getIdentifiers, getName, getRemarks, toWKT

Field Detail

WGS84

public static final DefaultEllipsoid WGS84

WGS 1984 ellipsoid with axis in metres. This ellipsoid is used in GPS systems and is the default for most org.geotools packages.

GRS80

public static final DefaultEllipsoid GRS80

GRS 80 ellipsoid with axis in metres.

Since:

2.2

INTERNATIONAL_1924

public static final DefaultEllipsoid INTERNATIONAL_1924

International 1924 ellipsoid with axis in metres.

CLARKE_1866

public static final DefaultEllipsoid CLARKE_1866

Clarke 1866 ellipsoid with axis in metres.

Since:

2.2

SPHERE

public static final DefaultEllipsoid SPHERE

A sphere with a radius of 6371000 metres. Spheres use a simplier algorithm for orthodromic distance computation, which may be faster and more robust.

Constructor Detail

DefaultEllipsoid

protected DefaultEllipsoid(Ellipsoid ellipsoid)

Constructs a new ellipsoid with the same values than the specified one. This copy constructor provides a way to wrap an arbitrary implementation into a Geotools 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:

ellipsoid - The ellipsoid to copy.

Since:

2.2

See Also:

wrap(org.geotools.api.referencing.datum.Ellipsoid)

DefaultEllipsoid

protected DefaultEllipsoid(Map<String,?> properties,
                           double semiMajorAxis,
                           double semiMinorAxis,
                           double inverseFlattening,
                           boolean ivfDefinitive,
                           Unit<Length> unit)

Constructs a new ellipsoid using the specified axis length. The properties map is given unchanged to the super-class constructor.

Parameters:

properties - Set of properties. Should contains at least "name".

semiMajorAxis - The equatorial radius.

semiMinorAxis - The polar radius.

inverseFlattening - The inverse of the flattening value.

ivfDefinitive - true if the inverse flattening is definitive.

unit - The units of the semi-major and semi-minor axis values.

See Also:

createEllipsoid(java.lang.String, double, double, javax.measure.Unit<javax.measure.quantity.Length>), createFlattenedSphere(java.lang.String, double, double, javax.measure.Unit<javax.measure.quantity.Length>)

Method Detail

createEllipsoid

public static DefaultEllipsoid createEllipsoid(String name,
                                               double semiMajorAxis,
                                               double semiMinorAxis,
                                               Unit<Length> unit)

Constructs a new ellipsoid using the specified axis length.

Parameters:

name - The ellipsoid name.

semiMajorAxis - The equatorial radius.

semiMinorAxis - The polar radius.

unit - The units of the semi-major and semi-minor axis values.

Returns:

An ellipsoid with the given axis length.

createEllipsoid

public static DefaultEllipsoid createEllipsoid(Map<String,?> properties,
                                               double semiMajorAxis,
                                               double semiMinorAxis,
                                               Unit<Length> unit)

Constructs a new ellipsoid using the specified axis length. The properties map is given unchanged to the super-class constructor.

Parameters:

properties - Set of properties. Should contains at least "name".

semiMajorAxis - The equatorial radius.

semiMinorAxis - The polar radius.

unit - The units of the semi-major and semi-minor axis values.

Returns:

An ellipsoid with the given axis length.

createFlattenedSphere

public static DefaultEllipsoid createFlattenedSphere(String name,
                                                     double semiMajorAxis,
                                                     double inverseFlattening,
                                                     Unit<Length> unit)

Constructs a new ellipsoid using the specified axis length and inverse flattening value.

Parameters:

name - The ellipsoid name.

semiMajorAxis - The equatorial radius.

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.

createFlattenedSphere

public static DefaultEllipsoid createFlattenedSphere(Map<String,?> properties,
                                                     double semiMajorAxis,
                                                     double inverseFlattening,
                                                     Unit<Length> unit)

Constructs a new ellipsoid using the specified axis length and inverse flattening value. The properties map is given unchanged to the super-class constructor.

Parameters:

properties - Set of properties. Should contains at least "name".

semiMajorAxis - The equatorial radius.

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.

wrap

public static DefaultEllipsoid wrap(Ellipsoid ellipsoid)

Wraps an arbitrary ellipsoid into a Geotools implementation. This method is usefull if orthodromic distance computation (for example) are desired. If the supplied ellipsoid is already an instance of DefaultEllipsoid or is null, then it is returned unchanged.

Parameters:

ellipsoid - The ellipsoid to wrap.

Returns:

The given ellipsoid as a DefaultEllipsoid instance.

getAxisUnit

public Unit<Length> getAxisUnit()

Returns the linear unit of the semi-major and semi-minor axis values.

Specified by:

getAxisUnit in interface Ellipsoid

Returns:

The axis linear unit.

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.

getEccentricity

public double getEccentricity()

The ratio of the distance between the center and a focus of the ellipse to the length of its semimajor axis. The eccentricity can alternately be computed from the equation: e=sqrt(2f-f²).

Returns:

The eccentricity of this ellipsoid.

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 = r_e/(r_e-r_p).

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

public double orthodromicDistance(Point2D P1,
                                  Point2D P2)

Returns the orthodromic distance between two geographic coordinates. The orthodromic distance is the shortest distance between two points on a sphere's surface. The default implementation delegates the work to orthodromicDistance(double,double,double,double).

Parameters:

P1 - Longitude and latitude of first point (in decimal degrees).

P2 - Longitude and latitude of second point (in decimal degrees).

Returns:

The orthodromic distance (in the units of this ellipsoid).

orthodromicDistance

public double orthodromicDistance(double x1,
                                  double y1,
                                  double x2,
                                  double y2)

Returns the orthodromic distance between two geographic coordinates. The orthodromic distance is the shortest distance between two points on a sphere's surface. The orthodromic path is always on a great circle. This is different from the loxodromic distance, which is a longer distance on a path with a constant direction on the compass.

Parameters:

x1 - Longitude of first point (in decimal degrees).

y1 - Latitude of first point (in decimal degrees).

x2 - Longitude of second point (in decimal degrees).

y2 - Latitude of second point (in decimal degrees).

Returns:

The orthodromic distance (in the units of this ellipsoid's axis).

equals

public boolean equals(AbstractIdentifiedObject object,
                      boolean compareMetadata)

Compare this ellipsoid with the specified object 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.

hashCode

public int hashCode()

Returns a hash value for this ellipsoid. Name, remarks and the like are not taken in account. In other words, two ellipsoids will return the same hash value if they are equal in the sense of equals(AbstractIdentifiedObject, false).

Overrides:

hashCode in class AbstractIdentifiedObject

Returns:

The hash code value. This value doesn't need to be the same in past or future versions of this class.

formatWKT

protected String formatWKT(Formatter formatter)

Format the inner part of a Well Known Text (WKT) element.

Overrides:

formatWKT in class Formattable

Parameters:

formatter - The formatter to use.

Returns:

The WKT element name, which is "SPHEROID"

See Also:

Formattable.toWKT(), Formattable.toString()

formatPROJ

public String formatPROJ(PROJFormatter formatter)

Description copied from interface: PROJFormattable

Format the inner part of a PROJFormattable object.

This method is automatically invoked by PROJFormatter.append(PROJFormattable).

For example for a element (DefaultOperationMethod) of type Projection, the formatter will invoke this method to prepend the "+proj=" String for completing the PROJ String before appending the Projection Name (e.g. lcc for a Lambert Conformal Conic)

Specified by:

formatPROJ in interface PROJFormattable

Parameters:

formatter - The PROJFormatter to use.

Returns:

The proj String of the PROJ element type if any. (e.g. +ellps= for named ellipsoids, +datum= for named datums).