Обновление MKMapView при обновлении местоположения пользователя или с использованием значений по умолчанию

I'm trying to refresh my map view and load new data from the server when the device acquires the user location. Here's what I'm doing:

- (void)viewDidLoad {
    CGRect bounds = self.view.bounds;
    mapView = [[MKMapView alloc] initWithFrame:bounds];
    mapView.showsUserLocation=YES;
    mapView.delegate=self;
    [self.view insertSubview:mapView atIndex:0];
    [self refreshMap];
}

- (void)mapView:(MKMapView *)theMapView didUpdateUserLocation:(MKUserLocation *)userLocation
{
    //this is to avoid frequent updates, I just need one position and don't need to continuously track the user's location
    if (userLocation.location.horizontalAccuracy > self.myUserLocation.location.horizontalAccuracy) {
        self.myUserLocation = userLocation;
        CLLocationCoordinate2D centerCoord = { userLocation.location.coordinate.latitude, userLocation.location.coordinate.longitude };
        [theMapView setCenterCoordinate:centerCoord zoomLevel:10 animated:YES];
        [self refreshMap];
    }
}

- (void)refreshMap {
    [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES];
    [self.mapView removeAnnotations:self.mapView.annotations];
    //default position
    NSString *lat = @"45.464161";
    NSString *lon = @"9.190336";
    if (self.myUserLocation != nil) {
        lat = [[NSNumber numberWithDouble:myUserLocation.coordinate.latitude] stringValue];
        lon = [[NSNumber numberWithDouble:myUserLocation.coordinate.longitude] stringValue];
    }
    NSString *url = [[NSString alloc] initWithFormat:@"http://myserver/geo_search.json?lat=%@&lon=%@", lat, lon];

    NSURLRequest *theRequest=[NSURLRequest requestWithURL:[NSURL URLWithString:url]
cachePolicy:NSURLRequestUseProtocolCachePolicy
timeoutInterval:60.0];
    [[NSURLConnection alloc] initWithRequest:theRequest delegate:self];
    [url release];
    [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO];
}

I also have a - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data, to create and add the annotations.

Here's what happens: sometimes I get the location after a while, so I already loaded data close to the default location. Затем я получаю местоположение, и он должен удалить старые аннотации и добавить новые, вместо этого я продолжаю видеть старые аннотации, а новые все равно добавляются (скажем, я получаю 10 аннотаций каждый раз, поэтому означает, что у меня на карте 20, а должно быть 10).

Что я делаю не так?