org.jxmapviewer.viewer.util.MercatorUtils Maven / Gradle / Ivy

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/*
 * MercatorUtils.java
 *
 * Created on October 7, 2006, 6:02 PM
 *
 * To change this template, choose Tools | Template Manager
 * and open the template in the editor.
 */

package org.jxmapviewer.viewer.util;

/**
 * A utility class of methods that help when 
 * dealing with standard Mercator projections.
 * @author [email protected]
 */
public final class MercatorUtils
{

    /** 
     * Creates a new instance of MercatorUtils 
     */
    private MercatorUtils()
    {
    }

    /**
     * @param longitudeDegrees the longitude in degrees
     * @param radius the world radius in pixels
     * @return the x value
     */
    public static int longToX(double longitudeDegrees, double radius)
    {
        double longitude = Math.toRadians(longitudeDegrees);
        return (int) (radius * longitude);
    }

    /**
     * @param latitudeDegrees the latitude in degrees
     * @param radius the world radius in pixels
     * @return the y value
     */
    public static int latToY(double latitudeDegrees, double radius)
    {
        double latitude = Math.toRadians(latitudeDegrees);
        double y = radius / 2.0 * Math.log((1.0 + Math.sin(latitude)) / (1.0 - Math.sin(latitude)));
        return (int) y;
    }

    /**
     * @param x the x value
     * @param radius the world radius in pixels
     * @return the longitude in degrees
     */
    public static double xToLong(int x, double radius)
    {
        double longRadians = x / radius;
        double longDegrees = Math.toDegrees(longRadians);
        /*
         * The user could have panned around the world a lot of times. Lat long goes from -180 to 180. So every time a
         * user gets to 181 we want to subtract 360 degrees. Every time a user gets to -181 we want to add 360 degrees.
         */
        int rotations = (int) Math.floor((longDegrees + 180) / 360);
        double longitude = longDegrees - (rotations * 360);
        return longitude;
    }

    /**
     * @param y the y value
     * @param radius the world radius in pixels
     * @return the latitude in degrees
     */
    public static double yToLat(int y, double radius)
    {
        double latitude = (Math.PI / 2) - (2 * Math.atan(Math.exp(-1.0 * y / radius)));
        return Math.toDegrees(latitude);
    }
}