func locationManager(_ manager: CLLocationManager, didChangeAuthorization status: CLAuthorizationStatus) {
        if status == .notDetermined || status == .denied || status == .authorizedWhenInUse {
            // present an alert indicating location authorization required
            // and offer to take the user to Settings for the app via
            // UIApplication -openUrl: and UIApplicationOpenSettingsURLString
            DispatchQueue.main.async(execute: {
                let alert = UIAlertController(title: "Error!", message: "GPS access is restricted. In order to use tracking, please enable GPS in the Settigs app under Privacy, Location Services.", preferredStyle: UIAlertControllerStyle.alert)
                alert.addAction(UIAlertAction(title: "Go to Settings now", style: UIAlertActionStyle.default, handler: { (alert: UIAlertAction!) in
                    print("")
                    UIApplication.shared.openURL(NSURL(string:UIApplicationOpenSettingsURLString)! as URL)
                }))
                // self.presentViewController(alert, animated: true, completion: nil)
                self.present(alert, animated: true, completion: nil)
            })
            manager.requestAlwaysAuthorization()
            manager.requestWhenInUseAuthorization()

        }
//        manager.startUpdatingHeading()
        manager.startMonitoringSignificantLocationChanges()

    }