void OnGUI()
        {
            c1a = GUILayout.TextField(c1a);
            c1o = GUILayout.TextField(c1o);
            c2a = GUILayout.TextField(c2a);
            c2o = GUILayout.TextField(c2o);

            try {
                var c1 = new Geolocation(
                    latitude: float.Parse(c1a),
                    longitude: float.Parse(c1o));
                var c2 = new Geolocation(
                    latitude: float.Parse(c2a),
                    longitude: float.Parse(c2o));
                GUILayout.Label(c1.Distance(c2).ToString());
            } catch (FormatException) {
                GUILayout.Label("FormatException");
            }
        }