Package org.geotools.referencing.operation.projection

Class AlbersEqualArea

Object

Formattable

AbstractMathTransform

MapProjection

AlbersEqualArea

All Implemented Interfaces:

Serializable, MathTransform, MathTransform2D

public class AlbersEqualArea
extends MapProjection

Albers Equal Area Projection (EPSG code 9822). This is a conic projection with parallels being unequally spaced arcs of concentric circles, more closely spaced at north and south edges of the map. Merideans are equally spaced radii of the same circles and intersect parallels at right angles. As the name implies, this projection minimizes distortion in areas.

The "standard_parallel_2" parameter is optional and will be given the same value as "standard_parallel_1" if not set (creating a 1 standard parallel projection).

NOTE: formulae used below are from a port, to Java, of the proj4 package of the USGS survey. USGS work is acknowledged here.

References:

• Proj-4.4.7 available at www.remotesensing.org/proj
  Relevent files are: PJ_aea.c, pj_fwd.c and pj_inv.c
• John P. Snyder (Map Projections - A Working Manual, U.S. Geological Survey Professional Paper 1395, 1987)
• "Coordinate Conversions and Transformations including Formulas", EPSG Guidence Note Number 7, Version 19.

Since:

2.1

Author:

Gerald I. Evenden (for original code in Proj4), Rueben Schulz

See Also:

• Albers Equal-Area Conic Projection on MathWorld
• "Albers_Conic_Equal_Area" on RemoteSensing.org
• British Columbia Albers Standard Projection
• Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	AlbersEqualArea.Provider	The math transform provider for an Albers Equal Area projection (EPSG code 9822).

Nested classes/interfaces inherited from class MapProjection

MapProjection.AbstractProvider

Field Summary

Fields inherited from class MapProjection

centralMeridian, en0, en1, en2, en3, en4, excentricity, excentricitySquared, falseEasting, falseNorthing, globalScale, invertible, isSpherical, latitudeOfOrigin, LOGGER, scaleFactor, semiMajor, semiMinor, SKIP_SANITY_CHECKS

Fields inherited from class Formattable

SINGLE_LINE

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	AlbersEqualArea(ParameterValueGroup parameters)	Constructs a new map projection from the supplied parameters.

Method Summary

Modifier and Type	Method	Description
boolean	equals(Object object)	Compares the specified object with this map projection for equality.
ParameterDescriptorGroup	getParameterDescriptors()	Returns the parameter descriptors for this map projection.
ParameterValueGroup	getParameterValues()	Returns the parameter values for this map projection.
int	hashCode()	Returns a hash value for this projection.
protected Point2D	inverseTransformNormalized(double x, double y, Point2D ptDst)	Transforms the specified (x,y) coordinates and stores the result in ptDst.
protected Point2D	transformNormalized(double x, double y, Point2D ptDst)	Transforms the specified (λ,φ) coordinates (units in radians) and stores the result in ptDst (linear distance on a unit sphere).

Methods inherited from class MapProjection

checkReciprocal, getSourceDimensions, getTargetDimensions, getToleranceForAssertions, inv_mlfn, inverse, mlfn, orthodromicDistance, resetWarnings, transform, transform, transform

Methods inherited from class AbstractMathTransform

createTransformedShape, derivative, derivative, ensureNonNull, formatWKT, getName, isIdentity, needCopy, normalizeAngle, rollLongitude, transform, transform, transform

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 MathTransform

derivative, isIdentity, toWKT, transform, transform, transform

Methods inherited from interface MathTransform2D

createTransformedShape, derivative

Constructor Details

AlbersEqualArea

protected AlbersEqualArea(ParameterValueGroup parameters)
                   throws ParameterNotFoundException

Constructs a new map projection from the supplied parameters.

Parameters:

parameters - The parameter values in standard units.

Throws:

ParameterNotFoundException - if a mandatory parameter is missing.

Method Details

getParameterDescriptors

public ParameterDescriptorGroup getParameterDescriptors()

Returns the parameter descriptors for this map projection. This is used for a providing a default implementation of MapProjection.getParameterValues(), as well as arguments checking.

Specified by:

getParameterDescriptors in class MapProjection

Returns:

The parameter descriptors for this math transform, or null.

See Also:

• OperationMethod.getParameters()

getParameterValues

public ParameterValueGroup getParameterValues()

Returns the parameter values for this map projection.

Overrides:

getParameterValues in class MapProjection

Returns:

A copy of the parameter values for this map projection.

See Also:

• Operation.getParameterValues()

transformNormalized

protected Point2D transformNormalized(double x,
 double y,
 Point2D ptDst)
                               throws ProjectionException

Transforms the specified (λ,φ) coordinates (units in radians) and stores the result in ptDst (linear distance on a unit sphere).

Specified by:

transformNormalized in class MapProjection

Parameters:

x - The longitude of the coordinate, in radians.

y - The latitude of the coordinate, in radians.

ptDst - the specified coordinate point that stores the result of transforming ptSrc, or null. Ordinates will be in a dimensionless unit, as a linear distance on a unit sphere or ellipse.

Returns:

the coordinate point after transforming (lambda, phi) and storing the result in ptDst.

Throws:

ProjectionException - if the point can't be transformed.

inverseTransformNormalized

protected Point2D inverseTransformNormalized(double x,
 double y,
 Point2D ptDst)
                                      throws ProjectionException

Transforms the specified (x,y) coordinates and stores the result in ptDst.

Specified by:

inverseTransformNormalized in class MapProjection

Parameters:

x - The easting of the coordinate, linear distance on a unit sphere or ellipse.

y - The northing of the coordinate, linear distance on a unit sphere or ellipse.

ptDst - the specified coordinate point that stores the result of transforming ptSrc, or null. Ordinates will be in radians.

Returns:

the coordinate point after transforming x, y and storing the result in ptDst.

Throws:

ProjectionException - if the point can't be transformed.

hashCode

public int hashCode()

Returns a hash value for this projection.

Overrides:

hashCode in class MapProjection

equals

public boolean equals(Object object)

Compares the specified object with this map projection for equality.

Overrides:

equals in class MapProjection

Parameters:

object - The object to compare with this transform.

Returns:

true if the given object is a transform of the same class and if, given identical source position, the transformed position would be the equals.