Package org.apache.sis.referencing.operation.projection

Class AzimuthalEquidistant

java.lang.Object

org.apache.sis.io.wkt.FormattableObject

org.apache.sis.referencing.operation.transform.AbstractMathTransform

org.apache.sis.referencing.operation.transform.AbstractMathTransform2D

org.apache.sis.referencing.operation.projection.NormalizedProjection

org.apache.sis.referencing.operation.projection.AzimuthalEquidistant

All Implemented Interfaces:

Serializable, Parameterized, LenientComparable, org.opengis.referencing.operation.MathTransform, org.opengis.referencing.operation.MathTransform2D

Direct Known Subclasses:

ModifiedAzimuthalEquidistant

public class AzimuthalEquidistant
extends NormalizedProjection

Azimuthal Equidistant (Spherical) projection. This projection method has no EPSG code. See the following references for an overview:

• Azimuthal equidistant projection on Wikipedia
• Azimuthal Equidistant Projection on MathWorld

Current implementation supports only the spherical case. For ellipsoidal formulas, the ModifiedAzimuthalEquidistant class provides an approximation valid under 800 kilometres of the projection centre.

Note of projection variants: formulas for this map projection have been published by Snyder (1987) in the following forms:

• Azimuthal Equidistant projection for the sphere. This form has no EPSG code. It is implemented in Apache SIS as "Azimuthal Equidistant (Spherical)".
• Polar aspect of ellipsoidal Azimuthal Equidistant. This form has no EPSG code. It is not yet implemented in Apache SIS.
• Oblique and equatorial aspects of ellipsoidal Azimuthal Equidistant:
  • Nearly rigorous sets of formulas. The EPSG name is "Modified Azimuthal Equidistant" (EPSG:9832). This projection is implemented by ModifiedAzimuthalEquidistant.
  • Approximate sets of formulas. The EPSG name is "Guam projection" (EPSG:9831). This projection is not yet implemented in Apache SIS.

This base class is aimed to provide the general case valid for all distances; the fact that current version uses spherical formulas should be considered as an implementation limitation that may change in future version. Subclasses are specialization for more restricted areas.

Since:

1.1

Version:

1.1

Author:

Martin Desruisseaux (Geomatys), Maxime Gavens (Geomatys)

See Also:

• ModifiedAzimuthalEquidistant
• Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.sis.referencing.operation.projection.NormalizedProjection

NormalizedProjection.ParameterRole

Field Summary

Fields inherited from class org.apache.sis.referencing.operation.projection.NormalizedProjection

eccentricity, eccentricitySquared

Fields inherited from class org.apache.sis.referencing.operation.transform.AbstractMathTransform2D

DIMENSION

Constructor Summary

Constructors

Constructor	Description
AzimuthalEquidistant(org.opengis.referencing.operation.OperationMethod method, Parameters parameters)	Creates a Azimuthal Equidistant projection from the given parameters.

Method Summary

Modifier and Type	Method	Description
protected void	inverseTransform(double[] srcPts, int srcOff, double[] dstPts, int dstOff)	Converts the specified (x,y) coordinates and stores the result in dstPts (angles in radians).
org.opengis.referencing.operation.Matrix	transform(double[] srcPts, int srcOff, double[] dstPts, int dstOff, boolean derivate)	Projects the specified (λ,φ) coordinates (units in radians) and stores the result in dstPts.

Methods inherited from class org.apache.sis.referencing.operation.projection.NormalizedProjection

computeHashCode, createMapProjection, equals, getContextualParameters, getParameterDescriptors, getParameterValues, inverse, tryConcatenate

Methods inherited from class org.apache.sis.referencing.operation.transform.AbstractMathTransform2D

createTransformedShape, derivative, getSourceDimensions, getTargetDimensions, transform

Methods inherited from class org.apache.sis.referencing.operation.transform.AbstractMathTransform

derivative, equals, formatTo, getDomain, hashCode, isIdentity, transform, transform, transform, transform, transform

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.operation.MathTransform

derivative, isIdentity, toWKT, transform, transform, transform, transform, transform

Constructor Details

AzimuthalEquidistant

public AzimuthalEquidistant(org.opengis.referencing.operation.OperationMethod method,
 Parameters parameters)

Creates a Azimuthal Equidistant projection from the given parameters. The method argument can be the description of one of the following:

• "Azimuthal Equidistant (Spherical)".

Parameters:

method - description of the projection parameters.

parameters - the parameter values of the projection to create.

Method Details

transform

public org.opengis.referencing.operation.Matrix transform(double[] srcPts,
 int srcOff,
 double[] dstPts,
 int dstOff,
 boolean derivate)
                                                   throws ProjectionException

Projects the specified (λ,φ) coordinates (units in radians) and stores the result in dstPts. In addition, opportunistically computes the projection derivative if derivate is true. The results must be multiplied by the denormalization matrix before to get linear distances.

Specified by:

transform in class NormalizedProjection

Parameters:

srcPts - source point coordinates, as (longitude, latitude) in radians.

srcOff - the offset of the single coordinate tuple to be converted in the source array.

dstPts - the array into which the converted coordinates is returned (may be the same than srcPts).

dstOff - the offset of the location of the converted coordinates that is stored in the destination array.

derivate - true for computing the derivative, or false if not needed.

Returns:

the matrix of the projection derivative at the given source position, or null if the derivate argument is false.

Throws:

ProjectionException - if the coordinates cannot be converted.

See Also:

• AbstractMathTransform.derivative(DirectPosition)
• AbstractMathTransform.transform(DirectPosition, DirectPosition)
• MathTransforms.derivativeAndTransform(MathTransform, double[], int, double[], int)

inverseTransform

protected void inverseTransform(double[] srcPts,
 int srcOff,
 double[] dstPts,
 int dstOff)
                         throws ProjectionException

Converts the specified (x,y) coordinates and stores the result in dstPts (angles in radians).

Specified by:

inverseTransform in class NormalizedProjection

Parameters:

srcPts - the array containing the source point coordinates, as linear distance on a unit sphere or ellipse.

srcOff - the offset of the point to be converted in the source array.

dstPts - the array into which the converted point coordinates is returned (may be the same than srcPts).

dstOff - the offset of the location of the converted point that is stored in the destination array.

Throws:

ProjectionException - if the point cannot be converted.