GoogleMapsProjection.java

import java.awt.Point;

/**
 * Contains the Google Maps map projection logic.
 * 
 * @author Irina Smidt, Simon Sprankel
 * @see http://de.slideshare.net/lodeblomme/google-maps-projection-and-how-to-use-it-for-clustering-presentation
 * @see https://developers.google.com/maps/documentation/javascript/maptypes#MapCoordinates
 */
public class GoogleMapsProjection {

	/**
	 * Converts the given longitude value to the x value of the Google Maps world coordinate.
	 * 
	 * @param lon the longitude value
	 * @return the x value of the corresponding Google Maps world coordinate
	 */
	public static Double lonToXWorld(Double lon) {
		Double tiles = Math.pow(2, 0);
		Double circumference = 256 * tiles;
		Double radius = circumference / (2 * Math.PI);
		Double falseEasting = -1.0 * circumference / 2.0;
		return (radius * Math.toRadians(lon)) - falseEasting;
	}

	/**
	 * Converts the given latitude value to the y value of the Google Maps world coordinate.
	 * 
	 * @param lat the latitude value
	 * @return the y value of the corresponding Google Maps world coordinate
	 */
	public static Double latToYWorld(Double lat) {
		Double tiles = Math.pow(2, 0);
		Double circumference = 256 * tiles;
		Double radius = circumference / (2 * Math.PI);
		Double falseNorthing = circumference / 2.0;
		return ((radius / 2.0 * Math.log((1.0 + Math.sin(Math.toRadians(lat)))
				/ (1.0 - Math.sin(Math.toRadians(lat))))) - falseNorthing)
				* -1;
	}

	/**
	 * Converts the given world coordinates to the pixel coordinates corresponding to the given zoom level.
	 * 
	 * @param xWorld the x value of the world coordinate
	 * @param yWorld the y value of the world coordinate
	 * @param zoomLevel the zoom level
	 * @return the pixel coordinates as a Point
	 */
	public static Point worldToPixel(Double xWorld, Double yWorld, int zoomLevel) {
		int zoom = (int) Math.pow(2, zoomLevel);
		int x = (int) Math.round(xWorld * zoom);
		int y = (int) Math.round(yWorld * zoom);
		return new Point(x, y);
	}

}