From 2a67f04d15bc7137d8dac509b929ba84fd2b99e5 Mon Sep 17 00:00:00 2001
From: Haoming Yin <hyi25@uclive.ac.nz>
Date: Wed, 26 Apr 2017 20:56:58 +1200
Subject: [PATCH] Create GeoUtility to process all geo calculations.

- calculate distance between two geo positions
- calculate the bearing from one geo position to another
- calculate the new geo position by passing original position, bearing and
distance

#story[828]
---
 .../seng302/server/simulator/GeoUtility.java  | 76 +++++++++++++++++++
 1 file changed, 76 insertions(+)
 create mode 100644 src/main/java/seng302/server/simulator/GeoUtility.java

diff --git a/src/main/java/seng302/server/simulator/GeoUtility.java b/src/main/java/seng302/server/simulator/GeoUtility.java
new file mode 100644
index 00000000..a93be4b3
--- /dev/null
+++ b/src/main/java/seng302/server/simulator/GeoUtility.java
@@ -0,0 +1,76 @@
+package seng302.server.simulator;
+
+import javafx.geometry.Pos;
+import seng302.server.simulator.mark.Mark;
+import seng302.server.simulator.mark.Position;
+
+public class GeoUtility {
+
+	private static double EARTH_RADIUS = 6378.137;
+	/**
+	 * Calculates the euclidean distance between two markers on the canvas using xy coordinates
+	 *
+	 * @param p1 first geographical position
+	 * @param p2 second geographical position
+	 * @return the distance in meter between two points in meters
+	 */
+	public static Double calculateMarkerDistance(Position p1, Position p2) {
+
+		double dLat = Math.toRadians(p2.getLat() - p1.getLat());
+		double dLon = Math.toRadians(p2.getLng() - p1.getLng());
+
+		double a = Math.pow(Math.sin(dLat / 2), 2.0)
+				+ Math.cos(Math.toRadians(p1.getLat())) * Math.cos(Math.toRadians(p2.getLat()))
+				* Math.pow(Math.sin(dLon / 2), 2.0);
+
+		double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
+		double d = EARTH_RADIUS * c;
+
+		return d * 1000; // distance from km to meter
+	}
+
+	/**
+	 * Calculates the angle between to angular co-ordinates on a sphere.
+	 *
+	 * @param p1 the first geographical position, start point
+	 * @param p2 the second geographical position, end point
+	 * @return the bearing in degree from p1 to p2, value range (0 ~ 360 deg.).
+	 *      vertical up is 0 deg. horizontal right is 90 deg.
+	 */
+	public static Double getBearing(Position p1, Position p2) {
+
+		double dLon = Math.toRadians(p2.getLng() - p1.getLng());
+
+		double y = Math.sin(dLon) * Math.cos(Math.toRadians(p2.getLat()));
+		double x = Math.cos(Math.toRadians(p1.getLat())) * Math.sin(Math.toRadians(p2.getLat()))
+				- Math.sin(Math.toRadians(p1.getLat())) * Math.cos(Math.toRadians(p2.getLat())) * Math.cos(dLon);
+
+		double bearing = Math.toDegrees(Math.atan2(y, x));
+
+		return (bearing + 360.0) % 360.0;
+	}
+
+	/**
+	 * Given an existing point in lat/lng, distance in (in meter) and bearing
+	 * (in degrees), calculates the new lat/lng.
+	 * @param origin the original position within lat / lng
+	 * @param bearing the bearing in degree, from original position to the new position
+	 * @param distance the distance in meter, from original position to the new position
+	 * @return the new position
+	 */
+	public static Position getGeoCoordinate(Position origin, Double bearing, Double distance) {
+		double b = Math.toRadians(bearing); // bearing to radians
+		double d = distance / 1000.0; // distance to km
+
+		double originLat = Math.toRadians(origin.getLat());
+		double originLng = Math.toRadians(origin.getLng());
+
+		double endLat = Math.asin(Math.sin(originLat) * Math.cos(d / EARTH_RADIUS)
+				+ Math.cos(originLat) * Math.sin(d / EARTH_RADIUS) * Math.cos(b));
+		double endLng = originLng
+				+ Math.atan2(Math.sin(b) * Math.sin(d / EARTH_RADIUS) * Math.cos(originLat),
+				Math.cos(d / EARTH_RADIUS) - Math.sin(originLat) * Math.sin(endLat));
+
+		return new Position(Math.toDegrees(endLat), Math.toDegrees(endLng));
+	}
+}