How to rotate a Direction Arrow to particular location

Question

In my app I have a latitude-longitude of 1 fix location. Now user with iPhone device can move anywhere and even he rotate his device, the arrow (some uiimageview) should poi

Answer 1

-(void)viewDidLoad
{
  locationManager = [[CLLocationManager alloc] init];
  locationManager.delegate = self;
  locationManager.desiredAccuracy = kCLLocationAccuracyBest;
  locationManager.distanceFilter = kCLDistanceFilterNone;
  [locationManager startUpdatingLocation];
  [locationManager startUpdatingHeading];
}
-(void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{
  GeoAngle = [self setLatLonForDistanceAndAngle:newLocation];
}

-(void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
{
   CLLocation *location=[locations lastObject];
   GeoAngle = [self setLatLonForDistanceAndAngle:location];
}
-(float)setLatLonForDistanceAndAngle:(CLLocation *)userlocation
{
   float lat1 = DegreesToRadians(userlocation.coordinate.latitude);
   float lon1 = DegreesToRadians(userlocation.coordinate.longitude);

   float lat2 = DegreesToRadians(Destination lattitude);
   float lon2 = DegreesToRadians(Destination Longitude);

   float dLon = lon2 - lon1;

   float y = sin(dLon) * cos(lat2);
   float x = cos(lat1) * sin(lat2) - sin(lat1) * cos(lat2) * cos(dLon);
   float radiansBearing = atan2(y, x);
   if(radiansBearing < 0.0)
   {
      radiansBearing += 2*M_PI;
   }
   return radiansBearing;
}

-(void)locationManager:(CLLocationManager *)manager didUpdateHeading:(CLHeading *)newHeading
{
   float direction = -newHeading.trueHeading;
   arrow.transform=CGAffineTransformMakeRotation((direction* M_PI / 180)+ GeoAngle);
}