/*
* GeoTools - The Open Source Java GIS Toolkit
* http://geotools.org
*
* (C) 1999-2008, Open Source Geospatial Foundation (OSGeo)
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation;
* version 2.1 of the License.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* This package contains formulas from the PROJ package of USGS.
* USGS's work is fully acknowledged here. This derived work has
* been relicensed under LGPL with Frank Warmerdam's permission.
*/
package org.geotools.referencing.operation.projection;
import java.awt.geom.Point2D;
import org.opengis.parameter.ParameterValueGroup;
import org.opengis.parameter.ParameterDescriptorGroup;
import org.opengis.parameter.ParameterNotFoundException;
import org.geotools.resources.i18n.ErrorKeys;
import static java.lang.Math.*;
/**
* The USGS equatorial case of the {@linkplain Stereographic stereographic} projection.
* This is a special case of oblique stereographic projection for
* {@linkplain #latitudeOfOrigin latitude of origin} == 0.0.
*
* @since 2.4
*
* @source $URL$
* @version $Id$
* @author André Gosselin
* @author Martin Desruisseaux (PMO, IRD)
* @author Rueben Schulz
*/
public class EquatorialStereographic extends StereographicUSGS {
/**
* For cross-version compatibility.
*/
private static final long serialVersionUID = -5098015759558831875L;
/**
* Maximum difference allowed when comparing real numbers.
*/
private static final double EPSILON = 1E-6;
/**
* A constant used in the transformations.
* This is <strong>not</strong> equal to the {@link #scaleFactor}.
*/
static final double k0 = 2;
/**
* Constructs an equatorial stereographic projection (EPSG equations).
*
* @param parameters The group of parameter values.
* @throws ParameterNotFoundException if a required parameter was not found.
*/
protected EquatorialStereographic(final ParameterValueGroup parameters)
throws ParameterNotFoundException
{
this(parameters, Stereographic.Provider.PARAMETERS);
}
/**
* Constructs an equatorial stereographic projection (USGS equations).
*
* @param parameters The group of parameter values.
* @param descriptor The expected parameter descriptor.
* @throws ParameterNotFoundException if a required parameter was not found.
*/
EquatorialStereographic(final ParameterValueGroup parameters,
final ParameterDescriptorGroup descriptor)
throws ParameterNotFoundException
{
super(parameters, descriptor);
assert super.k0 == k0 : super.k0;
latitudeOfOrigin = 0.0;
}
/**
* Transforms the specified (<var>λ</var>,<var>φ</var>) coordinates
* (units in radians) and stores the result in {@code ptDst} (linear distance
* on a unit sphere).
*/
@Override
protected Point2D transformNormalized(double x, double y, Point2D ptDst)
throws ProjectionException
{
// Compute using oblique formulas, for comparaison later.
assert (ptDst = super.transformNormalized(x, y, ptDst)) != null;
final double chi = 2.0 * atan(ssfn(y, sin(y))) - PI/2;
final double cosChi = cos(chi);
final double A = k0 / (1.0 + cosChi * cos(x)); // typo in (12-29)
x = A * cosChi * sin(x);
y = A * sin(chi);
assert checkTransform(x, y, ptDst);
if (ptDst != null) {
ptDst.setLocation(x,y);
return ptDst;
}
return new Point2D.Double(x,y);
}
/**
* Provides the transform equations for the spherical case of the
* equatorial stereographic projection.
*
* @version $Id$
* @author Martin Desruisseaux (PMO, IRD)
* @author Rueben Schulz
*/
static final class Spherical extends EquatorialStereographic {
/**
* For cross-version compatibility.
*/
private static final long serialVersionUID = -4790138052004333003L;
/**
* Constructs a spherical equatorial stereographic projection (USGS equations).
*
* @param parameters The group of parameter values.
* @param descriptor The expected parameter descriptor.
* @throws ParameterNotFoundException if a required parameter was not found.
*/
Spherical(final ParameterValueGroup parameters, final ParameterDescriptorGroup descriptor)
throws ParameterNotFoundException
{
super(parameters, descriptor);
ensureSpherical();
}
/**
* Transforms the specified (<var>λ</var>,<var>φ</var>) coordinates
* (units in radians) and stores the result in {@code ptDst} (linear distance
* on a unit sphere).
*/
@Override
protected Point2D transformNormalized(double x, double y, Point2D ptDst)
throws ProjectionException
{
// Compute using ellipsoidal formulas, for comparaison later.
assert (ptDst = super.transformNormalized(x, y, ptDst)) != null;
final double coslat = cos(y);
double f = 1.0 + coslat * cos(x);
if (f < EPSILON) {
throw new ProjectionException(ErrorKeys.VALUE_TEND_TOWARD_INFINITY);
}
f = k0 / f; // (21-14)
x = f * coslat * sin(x); // (21-2)
y = f * sin(y); // (21-13)
assert checkTransform(x, y, ptDst);
if (ptDst != null) {
ptDst.setLocation(x,y);
return ptDst;
}
return new Point2D.Double(x,y);
}
/**
* Transforms the specified (<var>x</var>,<var>y</var>) coordinate
* and stores the result in {@code ptDst}.
*/
@Override
protected Point2D inverseTransformNormalized(double x, double y,Point2D ptDst)
throws ProjectionException
{
// Compute using ellipsoidal formulas, for comparaison later.
assert (ptDst = super.inverseTransformNormalized(x, y, ptDst)) != null;
final double rho = hypot(x, y);
if (abs(rho) < EPSILON) {
y = 0.0; // latitudeOfOrigin
x = 0.0;
} else {
final double c = 2.0 * atan(rho / k0);
final double cosc = cos(c);
final double sinc = sin(c);
y = asin(y * sinc/rho); // (20-14) with phi1=0
final double t = x*sinc;
final double ct = rho*cosc;
x = (abs(t) < EPSILON && abs(ct) < EPSILON) ? 0.0 : atan2(t, ct);
}
assert checkInverseTransform(x, y, ptDst);
if (ptDst != null) {
ptDst.setLocation(x,y);
return ptDst;
}
return new Point2D.Double(x,y);
}
}
}