org.geotools.referencing.datum
Class DefaultEllipsoid

java.lang.Object
  org.geotools.referencing.wkt.Formattable
      org.geotools.referencing.AbstractIdentifiedObject
          org.geotools.referencing.datum.DefaultEllipsoid

All Implemented Interfaces:

org.opengis.referencing.datum.Ellipsoid, org.opengis.referencing.IdentifiedObject, java.io.Serializable

public class DefaultEllipsoid

extends AbstractIdentifiedObject

implements org.opengis.referencing.datum.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:

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

Since:

2.1

Version:

$Id: DefaultEllipsoid.java 17672 2006-01-19 00:25:55Z desruisseaux $

Author:

Martin Desruisseaux

See Also:

Serialized Form

Field Summary

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 org.geotools.referencing.AbstractIdentifiedObject

EMPTY_ALIAS_ARRAY, EMPTY_IDENTIFIER_ARRAY, IDENTIFIER_COMPARATOR, NAME_COMPARATOR, REMARKS_COMPARATOR

Fields inherited from interface org.opengis.referencing.IdentifiedObject

ALIAS_KEY, IDENTIFIERS_KEY, NAME_KEY, REMARKS_KEY

Constructor Summary

protected	DefaultEllipsoid(org.opengis.referencing.datum.Ellipsoid ellipsoid) Constructs a new ellipsoid with the same values than the specified one.
protected	DefaultEllipsoid(java.util.Map properties, double semiMajorAxis, double semiMinorAxis, double inverseFlattening, boolean ivfDefinitive, javax.units.Unit unit) Constructs a new ellipsoid using the specified axis length.

Method Summary

static DefaultEllipsoid	createEllipsoid(java.util.Map properties, double semiMajorAxis, double semiMinorAxis, javax.units.Unit unit) Constructs a new ellipsoid using the specified axis length.
static DefaultEllipsoid	createEllipsoid(java.lang.String name, double semiMajorAxis, double semiMinorAxis, javax.units.Unit unit) Constructs a new ellipsoid using the specified axis length.
static DefaultEllipsoid	createFlattenedSphere(java.util.Map properties, double semiMajorAxis, double inverseFlattening, javax.units.Unit unit) Constructs a new ellipsoid using the specified axis length and inverse flattening value.
static DefaultEllipsoid	createFlattenedSphere(java.lang.String name, double semiMajorAxis, double inverseFlattening, javax.units.Unit 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.
protected java.lang.String	formatWKT(Formatter formatter) Format the inner part of a Well Known Text (WKT) element.
javax.units.Unit	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() 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(java.awt.geom.Point2D P1, java.awt.geom.Point2D P2) Returns the orthodromic distance between two geographic coordinates.
static DefaultEllipsoid	wrap(org.opengis.referencing.datum.Ellipsoid ellipsoid) Wraps an arbitrary ellipsoid into a Geotools implementation.

Methods inherited from class org.geotools.referencing.AbstractIdentifiedObject

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

Methods inherited from class org.geotools.referencing.wkt.Formattable

toString, toWKT, toWKT, 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 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 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(org.opengis.referencing.datum.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.

Since:

2.2

See Also:

wrap(org.opengis.referencing.datum.Ellipsoid)

DefaultEllipsoid

protected DefaultEllipsoid(java.util.Map properties,
                           double semiMajorAxis,
                           double semiMinorAxis,
                           double inverseFlattening,
                           boolean ivfDefinitive,
                           javax.units.Unit 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 - 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.units.Unit), createFlattenedSphere(java.lang.String, double, double, javax.units.Unit)

Method Detail

createEllipsoid

public static DefaultEllipsoid createEllipsoid(java.lang.String name,
                                               double semiMajorAxis,
                                               double semiMinorAxis,
                                               javax.units.Unit 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.

createEllipsoid

public static DefaultEllipsoid createEllipsoid(java.util.Map properties,
                                               double semiMajorAxis,
                                               double semiMinorAxis,
                                               javax.units.Unit 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.

createFlattenedSphere

public static DefaultEllipsoid createFlattenedSphere(java.lang.String name,
                                                     double semiMajorAxis,
                                                     double inverseFlattening,
                                                     javax.units.Unit 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.

createFlattenedSphere

public static DefaultEllipsoid createFlattenedSphere(java.util.Map properties,
                                                     double semiMajorAxis,
                                                     double inverseFlattening,
                                                     javax.units.Unit 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.

wrap

public static DefaultEllipsoid wrap(org.opengis.referencing.datum.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 or is , then it is returned unchanged.

getAxisUnit

public javax.units.Unit getAxisUnit()

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

Specified by:

getAxisUnit in interface org.opengis.referencing.datum.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 org.opengis.referencing.datum.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 org.opengis.referencing.datum.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-f?).

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 ), the Double.POSITIVE_INFINITY value is used.

Specified by:

getInverseFlattening in interface org.opengis.referencing.datum.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 org.opengis.referencing.datum.Ellipsoid

Returns:

if the inverse flattening is definitive, or if the polar radius is definitive.

isSphere

public boolean isSphere()

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 org.opengis.referencing.datum.Ellipsoid

Returns:

if the ellipsoid is degenerate and is actually a sphere.

orthodromicDistance

public double orthodromicDistance(java.awt.geom.Point2D P1,
                                  java.awt.geom.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 degrees).

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

y1 - Latitude of first point (in degrees).

x2 - Longitude of second point (in degrees).

y2 - Latitude of second point (in 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 .

compareMetadata - for performing a strict comparaison, or for comparing only properties relevant to transformations.

Returns:

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 java.lang.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()