Application: gvSIG desktop » gvSIG geoprocess

/**

 * gvSIG. Desktop Geographic Information System.

 *

 * Copyright (C) 2007-2012 gvSIG Association.

 *

 * This program is free software; you can redistribute it and/or

 * modify it under the terms of the GNU General Public License

 * as published by the Free Software Foundation; either version 2

 * of the License, or (at your option) any later version.

 *

 * This program 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 General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,

 * MA  02110-1301, USA.

 *

 * For any additional information, do not hesitate to contact us

 * at info AT gvsig.com, or visit our website www.gvsig.com.

 */

package org.gvsig.geoprocess.algorithm.buffer;

import org.cresques.cts.IProjection;

import org.gvsig.fmap.mapcontext.MapContext;

/**

 * Abstract distance implementation.

 * 

 * @author gvSIG Team

 * @version $Id$

 */

public abstract class AbstractDistance implements IDistance {

    public static final double EARTH_RADIUS = 6378137d;

    /**

     * For computing with geodetic coordinates:

     * returns the angular measure (in radians)

     * for a distance over the earth along a

     * meridiam.

     * Because this consideration is an approximation,

     * we consideer the eart like an sphere (not an

     * ellipsoid)

     * 

     * @param dist

     *            distance in meters

     * @return arc of meridian whose length is the specified

     *         distance

     */

    private double toSexaAngularMeasure(double dist) {

        /*

         * dist = 6378km(terrestrial radius) -> 2PI

         * passed distance -> incognite

         */

        return Math.toDegrees((2 * Math.PI * dist) / EARTH_RADIUS);

    }

    /**

     * Converts a distance entered by user in the GUI in the same distance

     * in internal units (measure units)

     */

    protected double getInInternalUnits(double userEntryDistance,

        IProjection proj, int distanceUnits, int mapUnits) {

        double[] trans2Meter = MapContext.getDistanceTrans2Meter();

        double distInInternalUnits =

            (userEntryDistance / trans2Meter[mapUnits])

                * trans2Meter[distanceUnits];

        if ((proj != null) && !(proj.isProjected()))

            distInInternalUnits = toSexaAngularMeasure(distInInternalUnits);

        return distInInternalUnits;

    }

}