Ellipsoid.java

/* Geodesy by Mike Gavaghan
 * 
 * http://www.gavaghan.org/blog/free-source-code/geodesy-library-vincentys-formula/
 * 
 * This code may be freely used and modified on any personal or professional
 * project.  It comes with no warranty.
 */
package org.gavaghan.geodesy;

//import java.io.Serializable;

/**
 * Encapsulation of an ellipsoid, and declaration of common reference
 * ellipsoids.
 * 
 * @author Mike Gavaghan
 */
//public class Ellipsoid implements Serializable {
public class Ellipsoid {
	private static final long serialVersionUID = -2694307956656400089L;

	/** Semi major axis (meters). */
	private final double mSemiMajorAxis;

	/** Semi minor axis (meters). */
	private final double mSemiMinorAxis;

	/** Flattening. */
	private final double mFlattening;

	/** Inverse flattening. */
	private final double mInverseFlattening;

	/**
	 * Construct a new Ellipsoid. This is private to ensure the values are
	 * consistent (flattening = 1.0 / inverseFlattening). Use the methods
	 * fromAAndInverseF() and fromAAndF() to create new instances.
	 * 
	 * @param semiMajor
	 * @param semiMinor
	 * @param flattening
	 * @param inverseFlattening
	 */
	private Ellipsoid(double semiMajor, double semiMinor, double flattening, double inverseFlattening) {
		mSemiMajorAxis = semiMajor;
		mSemiMinorAxis = semiMinor;
		mFlattening = flattening;
		mInverseFlattening = inverseFlattening;
	}

	/** The WGS84 ellipsoid. */
	static public final Ellipsoid WGS84 = fromAAndInverseF(6378137.0, 298.257223563);

	/** The GRS80 ellipsoid. */
	static public final Ellipsoid GRS80 = fromAAndInverseF(6378137.0, 298.257222101);

	/** The GRS67 ellipsoid. */
	static public final Ellipsoid GRS67 = fromAAndInverseF(6378160.0, 298.25);

	/** The ANS ellipsoid. */
	static public final Ellipsoid ANS = fromAAndInverseF(6378160.0, 298.25);

	/** The WGS72 ellipsoid. */
	static public final Ellipsoid WGS72 = fromAAndInverseF(6378135.0, 298.26);

	/** The Clarke1858 ellipsoid. */
	static public final Ellipsoid Clarke1858 = fromAAndInverseF(6378293.645, 294.26);

	/** The Clarke1880 ellipsoid. */
	static public final Ellipsoid Clarke1880 = fromAAndInverseF(6378249.145, 293.465);

	/** A spherical "ellipsoid". */
	static public final Ellipsoid Sphere = fromAAndF(6371000, 0.0);

	/**
	 * Build an Ellipsoid from the semi major axis measurement and the inverse
	 * flattening.
	 * 
	 * @param semiMajor
	 *            semi major axis (meters)
	 * @param inverseFlattening
	 * @return
	 */
	static public Ellipsoid fromAAndInverseF(double semiMajor, double inverseFlattening) {
		double f = 1.0 / inverseFlattening;
		double b = (1.0 - f) * semiMajor;

		return new Ellipsoid(semiMajor, b, f, inverseFlattening);
	}

	/**
	 * Build an Ellipsoid from the semi major axis measurement and the
	 * flattening.
	 * 
	 * @param semiMajor
	 *            semi major axis (meters)
	 * @param flattening
	 * @return
	 */
	static public Ellipsoid fromAAndF(double semiMajor, double flattening) {
		double inverseF = 1.0 / flattening;
		double b = (1.0 - flattening) * semiMajor;

		return new Ellipsoid(semiMajor, b, flattening, inverseF);
	}

	/**
	 * Get semi-major axis.
	 * 
	 * @return semi-major axis (in meters).
	 */
	public double getSemiMajorAxis() {
		return mSemiMajorAxis;
	}

	/**
	 * Get semi-minor axis.
	 * 
	 * @return semi-minor axis (in meters).
	 */
	public double getSemiMinorAxis() {
		return mSemiMinorAxis;
	}

	/**
	 * Get flattening
	 * 
	 * @return
	 */
	public double getFlattening() {
		return mFlattening;
	}

	/**
	 * Get inverse flattening.
	 * 
	 * @return
	 */
	public double getInverseFlattening() {
		return mInverseFlattening;
	}
}