org.geotools.referencing.operation.projection
Class NewZealandMapGrid

java.lang.Object
  org.geotools.referencing.wkt.Formattable
      org.geotools.referencing.operation.transform.AbstractMathTransform
          org.geotools.referencing.operation.projection.MapProjection
              org.geotools.referencing.operation.projection.NewZealandMapGrid

All Implemented Interfaces:

org.opengis.referencing.operation.MathTransform, org.opengis.referencing.operation.MathTransform2D, java.io.Serializable

public class NewZealandMapGrid

extends MapProjection

Implementation of the NZMG (New Zealand Map Grid) projection.

This is an implementation of algorithm published by Land Information New Zealand. The algorithm is documented here.

Since:

2.2

Version:

$Id: NewZealandMapGrid.java 18048 2006-02-16 02:35:17Z desruisseaux $

Author:

Justin Deoliveira, Martin Desruisseaux

See Also:

Serialized Form

To Do:

The algorithm uses complex numbers, which is not very well supported in Java. This implementation uses Complex as a support class. Various instances of Complex are created once for ever at construction time, in order to avoid creating up to 6 objects for every point to be projected. The downside is that transformation methods must be synchronized. The cost should be small for simple applications, but may become important for multi-thread applications. Furthermore, those fields raise a slight serialization issue.

The most efficient fix in Java would be to expand inline all Complex operations like add (easy), multiply (more tedious), etc., until we get a code using only primitives on the stack and no Complex objects on the heap (except the and constants). But it would make the code significantly more complex and difficult to read.

An elegant fix would have been "lightweight objects" allocated on the stack (something similar to in C#), if such thing existed in the Java language.

Nested Class Summary

static class

NewZealandMapGrid.Provider The MathTransformProvider for New Zealand Map Grid.

Nested classes inherited from class org.geotools.referencing.operation.projection.MapProjection

MapProjection.AbstractProvider

Field Summary

Fields inherited from class org.geotools.referencing.operation.projection.MapProjection

centralMeridian, excentricity, excentricitySquared, falseEasting, falseNorthing, globalScale, isSpherical, latitudeOfOrigin, scaleFactor, semiMajor, semiMinor

Constructor Summary

protected	NewZealandMapGrid() Constructs a new map projection with default parameter values.
protected	NewZealandMapGrid(org.opengis.parameter.ParameterValueGroup parameters) Constructs a new map projection from the supplied parameters.

Method Summary

org.opengis.parameter.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.
protected java.awt.geom.Point2D	inverseTransformNormalized(double x, double y, java.awt.geom.Point2D ptDst) Transforms the specified (x,y) coordinate and stores the result in .
protected java.awt.geom.Point2D	transformNormalized(double x, double y, java.awt.geom.Point2D ptDst) Transforms the specified (x,y) coordinate (units in radians) and stores the result in (linear distance on a unit sphere).

Methods inherited from class org.geotools.referencing.operation.projection.MapProjection

equals, getParameterValues, getSourceDimensions, getTargetDimensions, getToleranceForAssertions, hashCode, inverse, transform, transform, transform

Methods inherited from class org.geotools.referencing.operation.transform.AbstractMathTransform

createTransformedShape, derivative, derivative, ensureNonNull, formatWKT, getDimSource, getDimTarget, isIdentity, needCopy, rollLongitude, transform

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.operation.MathTransform2D

createTransformedShape, derivative

Methods inherited from interface org.opengis.referencing.operation.MathTransform

derivative, isIdentity, toWKT, transform

Constructor Detail

NewZealandMapGrid

protected NewZealandMapGrid()

Constructs a new map projection with default parameter values.

NewZealandMapGrid

protected NewZealandMapGrid(org.opengis.parameter.ParameterValueGroup parameters)
                     throws org.opengis.parameter.ParameterNotFoundException

Constructs a new map projection from the supplied parameters.

Parameters:

parameters - The parameter values in standard units.

Throws:

org.opengis.parameter.ParameterNotFoundException - if a mandatory parameter is missing.

Method Detail

getParameterDescriptors

public org.opengis.parameter.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

transformNormalized

protected java.awt.geom.Point2D transformNormalized(double x,
                                                    double y,
                                                    java.awt.geom.Point2D ptDst)
                                             throws ProjectionException

Transforms the specified (x,y) coordinate (units in radians) and stores the result in (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 , or . Ordinates will be in a dimensionless unit, as a linear distance on a unit sphere or ellipse.

Returns:

the coordinate point after transforming , and storing the result in .

Throws:

ProjectionException - if the point can't be transformed.

inverseTransformNormalized

protected java.awt.geom.Point2D inverseTransformNormalized(double x,
                                                           double y,
                                                           java.awt.geom.Point2D ptDst)
                                                    throws ProjectionException

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

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 , or . Ordinates will be in radians.

Returns:

the coordinate point after transforming , and storing the result in .

Throws:

ProjectionException - if the point can't be transformed.