Adding distance display to the info windows.

htdocs/map.js

@@ -353,6 +353,23 @@ $(function(){
                 '">' + callsign + '</a>';
     };
 
+    var distanceKm = function(p1, p2) {
+        // Earth radius in km
+        var R = 6371.0;
+        // Convert degrees to radians
+        var rlat1 = p1.lat() * (Math.PI/180);
+        var rlat2 = p2.lat() * (Math.PI/180);
+        // Compute difference in radians
+        var difflat = rlat2-rlat1;
+        var difflon = (p2.lng()-p1.lng()) * (Math.PI/180);
+        // Compute distance
+        d = 2 * R * Math.asin(Math.sqrt(
+            Math.sin(difflat/2) * Math.sin(difflat/2) +
+            Math.cos(rlat1) * Math.cos(rlat2) * Math.sin(difflon/2) * Math.sin(difflon/2)
+        ));
+        return Math.round(d);
+    }
+
     var infowindow;
     var showLocatorInfoWindow = function(locator, pos) {
         var infowindow = getInfoWindow();
@@ -364,8 +381,10 @@ $(function(){
         }).sort(function(a, b){
             return b.lastseen - a.lastseen;
         });
+        var distance = receiverMarker?
+            " (at " + distanceKm(receiverMarker.position, pos) + "km)" : "";
         infowindow.setContent(
-            '<h3>Locator: ' + locator + '</h3>' +
+            '<h3>Locator: ' + locator + distance + '</h3>' +
             '<div>Active Callsigns:</div>' +
             '<ul>' +
                 inLocator.map(function(i){