ios - MKMapView オブザーバー

Question

この方法で 60 の MKMapViews にオブザーバーを追加しています。

[mapView2.userLocation addObserver:self
                                    forKeyPath:@"location"
                                       options:(NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld)

                                       context:NULL];

...

-(void)observeValueForKeyPath:(NSString *)keyPath  
                 ofObject:(id)object  
                   change:(NSDictionary *)change  
                  context:(void *)context {  

if ([self.mapView isUserLocationVisible]) { 

    static dispatch_once_t once;
    dispatch_once(&once, ^ { 
        // Code to run once

    MKCoordinateRegion mapRegion;   
    mapRegion.center = mapView.userLocation.coordinate;
    mapRegion.span.latitudeDelta = 0.01;
    mapRegion.span.longitudeDelta = 0.01;

    [mapView setRegion:mapRegion animated: YES];
    // and of course you can use here old and new location values

        });


    for (MKMapView *map in mapViewArray)
    {

        if ([map isUserLocationVisible]) { 


                // Code to run once

                MKCoordinateRegion mapRegion; 

            CLLocationCoordinate2D coordinate = [[map.annotations lastObject] coordinate];


                mapRegion.center = coordinate;
                mapRegion.span.latitudeDelta = 0.01;
                mapRegion.span.longitudeDelta = 0.01;

                [map setRegion:mapRegion animated: YES];
                // and of course you can use here old and new location values




        }
}}
}

それ以来、多くのメモリが消費されていることがわかります。これは多くのメモリを消費しますか？viewDidUnload でオブザーバーを削除するにはどうすればよいですか?