Created Mercator projection to convert between Geo location and planar projection point.

- MapGeo and MapPoint encapsulate geo location and planar projection point into classes.

#story[928]

src/main/java/seng302/models/map/MercatorProjection.java

@@ -0,0 +1,52 @@
+package seng302.models.map;
+
+public class MercatorProjection {
+
+	private double MERCATOR_RANGE = 256;
+	private double pixelsPerLngDegree, pixelsPerLngRadian;
+
+
+	public MercatorProjection() {
+		pixelsPerLngDegree = MERCATOR_RANGE / 360.0;
+		pixelsPerLngRadian = MERCATOR_RANGE / (2 * Math.PI);
+	}
+
+	/**
+	 * A help function keeps the value in bound between -0.9999 and 0.9999.
+	 * @param value in bound value
+	 * @return the value in bound
+	 */
+	private double bound(double value) {
+		return Math.min(Math.max(value, -0.9999), 0.9999);
+	}
+
+	/**
+	 * Projects a Geo Location (lat, lng) on a planar
+	 * @param geo MapGeo (lat, lng) location to be projected
+	 * @return the projection GeoPoint (x, y) on planar
+	 */
+	public MapPoint toMapPoint(MapGeo geo) {
+		MapPoint point = new MapPoint(0, 0);
+		MapPoint origin = new MapPoint(MERCATOR_RANGE / 2.0, MERCATOR_RANGE / 2.0);
+		point.setX(origin.getX() + geo.getLng() * pixelsPerLngDegree);
+
+//		NOTE(appleton): Truncating to 0.9999 effectively limits latitude to
+//      89.189.  This is about a third of a tile past the edge of the world tile.
+		double sinY = bound(Math.sin(Math.toRadians(geo.getLat())));
+		point.setY(origin.getY() + 0.5 * Math.log((1 + sinY) / (1 - sinY)) * (-pixelsPerLngRadian));
+		return point;
+	}
+
+	/**
+	 * Converts the planar projection (x, y) back to Geo Location (lat, lng)
+	 * @param point MapPoint (x, y) to be converted back
+	 * @return the original Geo location converted from the given projection point
+	 */
+	public MapGeo toMapGeo(MapPoint point) {
+		MapPoint origin = new MapPoint(MERCATOR_RANGE / 2.0, MERCATOR_RANGE / 2.0);
+		double lng = (point.getX() - origin.getX()) / pixelsPerLngDegree;
+		double latRadians = (point.getY() - origin.getY()) / (-pixelsPerLngRadian);
+		double lat = Math.toDegrees(2 * Math.atan(Math.exp(latRadians)) - Math.PI / 2.0);
+		return new MapGeo(lat, lng);
+	}
+}