projmath.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/ProjMath.java,v $
// $RCSfile: ProjMath.java,v $
// $Revision: 1.3.2.2 $
// $Date: 2005/02/11 22:51:27 $
// $Author: dietrick $
// 
// **********************************************************************

package com.bbn.openmap.proj;

import com.bbn.openmap.MoreMath;

/**
 * Math functions used by projection code.
 */
public final class ProjMath {

    /**
     * North pole latitude in radians.
     */
    public final static transient float NORTH_POLE_F = MoreMath.HALF_PI;

    /**
     * South pole latitude in radians.
     */
    public final static transient float SOUTH_POLE_F = -NORTH_POLE_F;

    /**
     * North pole latitude in radians.
     */
    public final static transient double NORTH_POLE_D = MoreMath.HALF_PI_D;

    /**
     * South pole latitude in radians.
     */
    public final static transient double SOUTH_POLE_D = -NORTH_POLE_D;

    /**
     * Dateline longitude in radians.
     */
    public final static transient float DATELINE_F = (float) Math.PI;

    /**
     * Dateline longitude in radians.
     */
    public final static transient double DATELINE_D = Math.PI;

    /**
     * Longitude range in radians.
     */
    public final static transient float LON_RANGE_F = (float) MoreMath.TWO_PI;

    /**
     * Longitude range in radians.
     */
    public final static transient double LON_RANGE_D = MoreMath.TWO_PI_D;

    // cannot construct
    private ProjMath() {}

    /**
     * rounds the quantity away from 0.
     * 
     * @param x in value
     * @return double
     * @see #qint(double)
     */
    public final static double roundAdjust(double x) {
        return qint_old(x);
    }

    /**
     * Rounds the quantity away from 0.
     * 
     * @param x value
     * @return double
     */
    public final static double qint(double x) {
        return qint_new(x);
    }

    final private static double qint_old(double x) {
        return (((int) x) < 0) ? (x - 0.5) : (x + 0.5);
    }

    final private static double qint_new(double x) {
        // -1 or +1 away from zero
        return (x <= 0.0) ? (x - 1.0) : (x + 1.0);
    }

    /**
     * Calculate the shortest arc distance between two lons.
     * 
     * @param lon1 radians
     * @param lon2 radians
     * @return float distance
     */
    public final static float lonDistance(float lon1, float lon2) {
        return (float) Math.min(Math.abs(lon1 - lon2), ((lon1 < 0) ? lon1
                + Math.PI : Math.PI - lon1)
                + ((lon2 < 0) ? lon2 + Math.PI : Math.PI - lon2));
    }

    /**
     * Convert between decimal degrees and scoords.
     * 
     * @param deg degrees
     * @return long scoords
     *  
     */
    public final static long DEG_TO_SC(double deg) {
        return (long) (deg * 3600000);
    }

    /**
     * Convert between decimal degrees and scoords.
     * 
     * @param sc scoords
     * @return double decimal degrees
     */
    public final static double SC_TO_DEG(int sc) {
        return ((double) (sc) / (60.0 * 60.0 * 1000.0));
    }

    /**
     * Convert radians to degrees.
     * 
     * @param rad radians
     * @return double decimal degrees
     */
    public final static double radToDeg(double rad) {
        return (rad * (180.0d / Math.PI));
    }

    /**
     * Convert radians to degrees.
     * 
     * @param rad radians
     * @return float decimal degrees
     */
    public final static float radToDeg(float rad) {
        return (float) radToDeg((double)rad);
    }

    /**
     * Convert degrees to radians.
     * 
     * @param deg degrees
     * @return double radians
     */
    public final static double degToRad(double deg) {
        return (deg * (Math.PI / 180.0d));
    }

    /**
     * Convert degrees to radians.
     * 
     * @param deg degrees
     * @return float radians
     */
    public final static float degToRad(float deg) {
        return (float) degToRad((double)deg);
    }

    /**
     * Generate a hashCode value for a lat/lon pair.
     * 
     * @param lat latitude
     * @param lon longitude
     * @return int hashcode
     *  
     */
    public final static int hashLatLon(float lat, float lon) {
        if (lat == -0f)
            lat = 0f;//handle negative zero (anything else?)
        if (lon == -0f)
            lon = 0f;
        int tmp = Float.floatToIntBits(lat);
        int hash = (tmp << 5) | (tmp >> 27);//rotate the lat bits
        return hash ^ Float.floatToIntBits(lon);//XOR with lon
    }

    /**
     * Converts an array of decimal degrees float lat/lons to float
     * radians in place.
     * 
     * @param degs float[] lat/lons in decimal degrees
     * @return float[] lat/lons in radians
     */
    public final static float[] arrayDegToRad(float[] degs) {
        for (int i = 0; i < degs.length; i++) {
            degs[i] = degToRad(degs[i]);
        }
        return degs;
    }

    /**
     * Converts an array of radian float lat/lons to decimal degrees
     * in place.
     * 
     * @param rads float[] lat/lons in radians
     * @return float[] lat/lons in decimal degrees
     */
    public final static float[] arrayRadToDeg(float[] rads) {
        for (int i = 0; i < rads.length; i++) {
            rads[i] = radToDeg(rads[i]);
        }
        return rads;
    }

    /**
     * Converts an array of decimal degrees double lat/lons to double
     * radians in place.
     * 
     * @param degs double[] lat/lons in decimal degrees
     * @return double[] lat/lons in radians
     */
    public final static double[] arrayDegToRad(double[] degs) {
        for (int i = 0; i < degs.length; i++) {
            degs[i] = degToRad(degs[i]);
        }
        return degs;
    }