Merge pull request #22 from pavloDeshko/base

utils changes

Author: elliotstokes

lib/geomUtils.js

@@ -11,6 +11,20 @@ if (!Number.prototype.toRad) {
 
 }
 
+if (!Number.prototype.toDeg) {
+	Number.prototype.toDeg = function() {
+		return this * 180/ Math.PI;
+	};
+
+}
+
+if(!Number.prototype.roundTo){
+    Number.prototype.roundTo = function(place){
+      var exp = Math.pow(10,place);
+      return Math.round(this * exp) / exp;
+    };
+}
+
 var greatCircleRadius = {
 	miles: 3956,
 	km: 6367
@@ -20,11 +34,12 @@ var greatCircleRadius = {
  * Calculates the distance between the two points using the haversine method.
  * @param {number} lat1 The latitude of the first point.
  * @param {number} lon1 The longtitude of the first point.
- * @param {number} lat2 The latitude of the first point.
- * @param {number} lon2 The longtitude of the first point.
- * @returns {number} The distance in miles between the two points.
+ * @param {number} lat2 The latitude of the second point.
+ * @param {number} lon2 The longtitude of the second point.
+ * @param {boolean} [inMiles=False] Specifies if result should be in miles.
+ * @returns {number} The distance in kilometers (or miles) between the two points.
 **/
-exports.calculateDistance = function(lat1, lon1, lat2, lon2) {
+exports.calculateDistance = function(lat1, lon1, lat2, lon2, inMiles) {
 	var dLat = (lat2 - lat1).toRad(),
 		dLon = (lon2 - lon1).toRad();
 
@@ -34,26 +49,47 @@ exports.calculateDistance = function(lat1, lon1, lat2, lon2) {
 	var a = Math.sin(dLat / 2) * Math.sin(dLat / 2) +
 		Math.sin(dLon / 2) * Math.sin(dLon / 2) * Math.cos(lat1) * Math.cos(lat2);
 	var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
-	return greatCircleRadius.km * c;
+	return (inMiles ? greatCircleRadius.miles : greatCircleRadius.km) * c;
 };
 
 /**
- * Calcuates the midpoint between the two points passed in.
+ * Calculates the midpoint between the two points passed in.
  * @param {number} lat1 The latitude of the first point.
  * @param {number} lon1 The longtitude of the first point.
- * @param {number} lat2 The latitude of the first point.
- * @param {number} lon2 The longtitude of the first point.
+ * @param {number} lat2 The latitude of the second point.
+ * @param {number} lon2 The longtitude of the second point.
+ * @returns {Array<number>} An array of lat and lon values of the midpoint, rounded to 8th dec place.
  */
 exports.calculateMidpoint = function(lat1, lon1, lat2, lon2) {
-	var dLat = (lat2 - lat1).toRad(),
-		dLon = (lon2 - lon1).toRad();
-
-	lat1 = lat1.toRad();
+    var dLon = (lon2 - lon1).toRad();
+  
+    lat1 = lat1.toRad();
 	lat2 = lat2.toRad();
-
-	var Bx = Math.cos(lat2) * Math.cos(dLon);
+  
+    var Bx = Math.cos(lat2) * Math.cos(dLon);
 	var By = Math.cos(lat2) * Math.sin(dLon);
-	var lat3 = Math.atan2(Math.sin(lat1) + Math.sin(lat2),
-		Math.sqrt((Math.cos(lat1) + Bx) * (Math.cos(lat1) + Bx) + By * By));
-	var lon3 = lon1 + Math.atan2(By, Math.cos(lat1) + Bx);
+
+	var lat3 = (Math.atan2(Math.sin(lat1) + Math.sin(lat2),
+		Math.sqrt((Math.cos(lat1) + Bx) * (Math.cos(lat1) + Bx) + By * By))).toDeg();
+	var lon3 = lon1 + Math.atan2(By, Math.cos(lat1) + Bx).toDeg();
+	return [lat3.roundTo(8),lon3.roundTo(8)]; //rounding also solves f-point precision issues
 };
+
+/*
+Calculates bearing from the first point to the second point passed in.
+ * @param {number} lat1 The latitude of the first point.
+ * @param {number} lon1 The longtitude of the first point.
+ * @param {number} lat2 The latitude of the second point.
+ * @param {number} lon2 The longtitude of the second point.
+ * @returns {number} Initial compass (0 ... 360) bearing in decimal degrees.
+*/
+exports.calculateBearing = function(lat1, lon1, lat2, lon2){
+  var dLon = (lon2-lon1).toRad();
+  
+  lat1 = lat1.toRad();
+  lat2 = lat2.toRad();
+  
+  var bearing = Math.atan2(Math.sin(dLon)*Math.cos(lat2), Math.cos(lat1)*Math.sin(lat2) - 
+                          Math.sin(lat1)*Math.cos(lat2)*Math.cos(dLon));
+  return ((bearing.toDeg() + 360) % 360).roundTo(9); // converts from 180 .. -180 range
+}

tests/utils-tests.js

@@ -11,13 +11,31 @@ module.exports = {
     },
 
     "Should calculate the distance between two points": function(test) {
-        var distance = geomUtils.calculateDistance(4.367, 5.6745, -40.4556, 39.34345);
-        test.equal(distance, 6045.97811789512);
+        var distanceInKm = geomUtils.calculateDistance(4.367, 5.6745, -40.4556, 39.34345);
+        var distanceInMiles = geomUtils.calculateDistance(4.367, 5.6745, -40.4556, 39.34345, true);
+        
+        test.equal(distanceInKm, 6045.97811789512);
+        test.equal(distanceInMiles, distanceInKm/1.609453993933266 ); 
         test.done();
     },
 
     "Should calculate the midpoint between two points" : function(test) {
-        geomUtils.calculateMidpoint(4.367, 5.6745, -40.4556, 39.34345);
+        var midpoint = geomUtils.calculateMidpoint(4.367, 5.6745, -40.4556, 39.34345);
+        test.deepEqual(midpoint, [-18.78213486, 20.18113593]);
+        test.done();
+    },
+    
+    "Should calculate bearing from one point to other" : function(test){
+        var bearingWest = geomUtils.calculateBearing(0, 40, 0, 50);
+        test.equal(bearingWest, 90);
+      
+        var bearingNorth= geomUtils.calculateBearing(-50, -40, 50, -40);
+        test.equal(bearingNorth, 0);
+      
+        var bearing  = geomUtils.calculateBearing(4.367, 5.6745, -40.4556, 39.34345);
+        test.equal(bearing, 148.750703805);
+        
         test.done();
     }
 };
+