- (MKAnnotationView *)mapView:(MKMapView *)theMapView viewForAnnotation:(id <MKAnnotation>)annotation {
  // if it's the user location, just return nil.
  if ([annotation isKindOfClass:[MKUserLocation class]]){
    return nil;
  }

  MKAnnotationView *pinView = [map viewForAnnotation:annotation];
  PersonPin *pin = (PersonPin*)annotation;

  if (!pinView || pin.needsDisplay) {
    MKAnnotationView *annotationView =
      [[MKAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:annotationIdentifier];

    UIImage *image;
    image = [UIImage imageNamed:[pin getPinImage]];
    UIImage *resizedImage = [pin sizePinToFitMap:image bounds:self.view.bounds];
    annotationView.image = resizedImage;
    annotationView.canShowCallout = YES;
    annotationView.annotation = annotation;
    annotationView.opaque = NO;
    return annotationView;
  } else {
    pinView.annotation = annotation;
  }
  return pinView;
}