title: Draw a circle of 1000m radius around users location in MKMapView
body: <p><em>(Using iOS 5 and Xcode 4.2)</em></p>
  
  <p>I have an MKMapView and want to draw a circle of 1000m radius around the user location.</p>
  
  <p>On the surface it would seem that implementing the <a href="http://developer.apple.com/library/ios/#documentation/MapKit/Reference/MKMapViewDelegate_Protocol/MKMapViewDelegate/MKMapViewDelegate.html#//apple_ref/doc/uid/TP40008204" rel="noreferrer">mapView:viewForAnnotation:</a>  map view delegate method, and adding a custom MKAnnotationView for the users location, would be a perfect solution. It would look something like this:</p>
  
  <pre><code>- (MKAnnotationView *)mapView:(MKMapView *)mapView
              viewForAnnotation:(id &lt;MKAnnotation&gt;)annotation
  {
      // If it's the user location, return my custom MKAnnotationView.
      if ([annotation isKindOfClass:[MKUserLocation class]]) {
          return myCustomAnnotationView;
      } else {
          return nil;
      }
  }
  </code></pre>
  
  <p>However annotations on the map don't scale when you zoom in and out of the map. </p>
  
  <p>So I tried adding an overlay (because overlays scale with the map), using the <a href="http://developer.apple.com/library/IOs/#documentation/MapKit/Reference/MKCircle_class/Reference/Reference.html" rel="noreferrer">MKCircle</a> class and setting its co-ordinates to the latest co-ordinates from my locationManger/map view delegate. However as the <a href="http://developer.apple.com/library/IOs/#documentation/MapKit/Reference/MKCircle_class/Reference/Reference.html" rel="noreferrer">coordinate property</a> of MKCircle is readonly, I'm having to remove the overlay then add a new one each time the user moves. Causing a noticeable flicker as it happens.</p>
  
  <p>Is there any way to make an annotation scale seamlessly as the map view is scaled in and out? Or is there a good way to make an overlay move seamlessly with changes in the users location?</p>
  
  <p>I would be very grateful for your help :)</p>