1 files changed, 52 insertions, 0 deletions
diff --git a/lib/address.js b/lib/address.js
index 21e14ff6..e7cc053a 100644
--- a/lib/address.js
+++ b/lib/address.js
@@ -289,6 +289,58 @@ function Address (faker) {
     "sampleResults": ["Northwest", "Southeast", "SW", "NE"]
   };
 
+  this.nearbyGPSCoordinate = function(coordinate, radius, isMetric) {
+        function randomFloat(min, max) {
+            return Math.random() * (max-min) + min;
+        }
+        function degreesToRadians(degrees) {
+            return degrees * (Math.PI/180.0);
+        }
+        function radiansToDegrees(radians) {
+            return radians * (180.0/Math.PI);
+        }
+        function kilometersToMiles(miles) {
+            return miles * 0.621371;
+        }
+        function coordinateWithOffset(coordinate, bearing, distance, isMetric) {
+            var R = 6378.137; // Radius of the Earth (http://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html)
+            var d = isMetric ? distance : kilometersToMiles(distance); // Distance in km
+
+            var lat1 = degreesToRadians(coordinate[0]); //Current lat point converted to radians
+            var lon1 = degreesToRadians(coordinate[1]); //Current long point converted to radians
+
+            var lat2 = Math.asin(Math.sin(lat1) * Math.cos(d/R) +
+                Math.cos(lat1) * Math.sin(d/R) * Math.cos(bearing));
+
+            var lon2 = lon1 + Math.atan2(
+                Math.sin(bearing) * Math.sin(d/R) * Math.cos(lat1),
+                Math.cos(d/R) - Math.sin(lat1) * Math.sin(lat2));
+
+            // Keep longitude in range [-180, 180]
+            if (lon2 > degreesToRadians(180)) {
+                lon2 = lon2 - degreesToRadians(360);
+            } else if (lon2 < degreesToRadians(-180)) {
+                lon2 = lon2 + degreesToRadians(360);
+            }
+
+            return [radiansToDegrees(lat2), radiansToDegrees(lon2)];
+        }
+
+        // If there is no coordinate, the best we can do is return a random GPS coordinate.
+        if (coordinate === undefined) {
+            return [this.latitude(), this.longitude()]
+        }
+        radius = radius || 10.0;
+        isMetric = isMetric || false;
+
+        // TODO: implement either a gaussian/uniform distribution of points in cicular region.
+        // Possibly include param to function that allows user to choose between distributions.
+
+        // This approach will likely result in a higher density of points near the center.
+        var randomCoord = coordinateWithOffset(coordinate, degreesToRadians(Math.random() * 360.0), radius, isMetric);
+        return [randomCoord[0].toFixed(4), randomCoord[1].toFixed(4)];
+    }
+
   return this;
 }