length.java

openmap java写的开源数字地图程序. 用applet实现,可以像google map 那样放大缩小地图.

// **********************************************************************
// 
// <copyright>
// 
//  BBN Technologies
//  10 Moulton Street
//  Cambridge, MA 02138
//  [phone]
// 
//  Copyright (C) BBNT Solutions LLC. All rights reserved.
// 
// </copyright>
// **********************************************************************
// 
// $Source: /cvs/distapps/openmap/src/openmap/com/bbn/openmap/proj/Length.java,v $
// $RCSfile: Length.java,v $
// $Revision: 1.5.2.2 $
// $Date: 2005/08/10 22:45:12 $
// $Author: dietrick $
// 
// **********************************************************************

package com.bbn.openmap.proj;

import com.bbn.openmap.Environment;
import com.bbn.openmap.I18n;
import com.bbn.openmap.util.Debug;

/**
 * Length is a convenience class used for a couple of things. It can
 * be used to specifiy unit type, and can be used for conversion from
 * radians to/from whatever units are represented by the implemented
 * class.
 */
public class Length {

    /** Miles, in WGS 84 spherical earth model units. */
    public final static Length MILE = new Length("mile", "miles", Planet.wgs84_earthEquatorialCircumferenceMiles_D);
    /** Feet, in WGS 84 spherical earth model units. */
    public final static Length FEET = new Length("feet", "feet", Planet.wgs84_earthEquatorialCircumferenceMiles_D * 5280.0);
    /** Meters, in WGS 84 Spherical earth model units. */
    public final static Length METER = new Length("meter", "m", Planet.wgs84_earthEquatorialCircumferenceMeters_D);
    /** Kilometers, in WGS 84 Spherical earth model units. */
    public final static Length KM = new Length("kilometer", "km", Planet.wgs84_earthEquatorialCircumferenceKM_D);
    /** Nautical Miles, in WGS 84 Spherical earth model units. */
    public final static Length NM = new Length("nautical mile", "nm", Planet.wgs84_earthEquatorialCircumferenceNMiles_D);
    /** Decimal Degrees, in WGS 84 Spherical earth model units. */
    public final static Length DECIMAL_DEGREE = new Length("decimal degree", "deg", 360.0);
    /** Radians, in terms of a spherical earth. */
    public final static Length RADIAN = new Length("radian", "rad", com.bbn.openmap.MoreMath.TWO_PI_D);
    /** Data Mile, in WGS 84 spherical earth model units. */
    public final static Length DM = new Length("datamile", "dm", Planet.wgs84_earthEquatorialCircumferenceMiles_D * 5280.0 / 6000.0);

    /** Unit/radians */
    protected final double constant;
    protected final String name;
    protected final String abbr;
    protected double unitEquatorCircumference;
    protected I18n i18n = Environment.getI18n();

    /**
     * Create a Length, with a name an the number of it's units that
     * go around the earth at its equator. The name and abbreviation
     * are converted to lower case for consistency.
     */
    public Length(String name, String abbr, double unitEquatorCircumference) {
        this.name = i18n.get(this, abbr + ".name", name).toLowerCase().intern();
        this.unitEquatorCircumference = unitEquatorCircumference;
        this.constant = unitEquatorCircumference / com.bbn.openmap.MoreMath.TWO_PI_D;
        this.abbr = abbr.toLowerCase().intern();
    }

    /**
     * Given a number of units provided by this Length, convert to a
     * number of radians.
     */
    public float toRadians(float numUnits) {
        if (Debug.debugging("length")) {
            Debug.output("Translating " + name + " from radians");
        }

        return numUnits / (float) constant;
    }

    public double toRadians(double numUnits) {
        if (Debug.debugging("length")) {
            Debug.output("Translating " + name + " from radians");
        }

        return numUnits / constant;
    }

    /**
     * Given a number of radians, convert to the number of units
     * represented by this length.
     */
    public float fromRadians(float numRadians) {
        if (Debug.debugging("length")) {
            Debug.output("Translating radians from " + name);
        }

        return numRadians * (float) constant;
    }

    /**
     * Given a number of radians, convert to the number of units
     * represented by this length.
     */
    public double fromRadians(double numRadians) {
        if (Debug.debugging("length")) {
            Debug.output("Translating radians from " + name);
        }

        return numRadians * constant;
    }

    /**
     * Return the name for this length type.
     */
    public String toString() {
        return name;
    }

    /**
     * Return the abbreviation for this length type.
     */
    public String getAbbr() {
        return abbr;
    }

    /**
     * Get a list of the Lengths currently defined as static
     * implementations of this class.
     */
    public static Length[] getAvailable() {
        return new Length[] { METER, KM, FEET, MILE, DM, NM, DECIMAL_DEGREE };
    }

    /**
     * Get the Length object with the given name or abbreviation. If
     * nothing exists with that name, then return null. The lower case
     * version of the name or abbreviation is checked against the
     * available options.
     */
    public static Length get(String name) {
        Length[] choices = getAvailable();

        for (int i = 0; i < choices.length; i++) {
            if (name.toLowerCase().intern() == choices[i].toString()
                    || name.toLowerCase().intern() == choices[i].getAbbr()) {
                return choices[i];
            }
        }
        return null;
    }
}