Question

Im Having MapView In which I added some 5 Annotations in the Areas of Chennai.. I want to Zoom Out the Chennai as soon as the MapView Begins Loading so that Annotations will be Visible Clearly.
In viewDidLoad:

CLLocationCoordinate2D location6;
    location6.latitude=12.9758;
    location6.longitude=80.2205;
    MapAnnotation *ann6=[[MapAnnotation alloc]initWithTitle:@"Chennai-Velacherry" andCoordinate:location6];
    [mapView addAnnotation:ann6];

     CLLocationCoordinate2D centerlocation;
    centerlocation.longitude=13.0810;
    centerlocation.longitude=80.2740;


    [mapView setCenterCoordinate:centerlocation animated:NO];
     [self.view addSubview:mapView];

Answer 1

use this,

        MKCoordinateRegion region = { {0.0, 0.0 }, { 0.0, 0.0 } }; 
        region.center.latitude = [currentPlace.latitude doubleValue];
        region.center.longitude = [currentPlace.longitude doubleValue];
        region.span.longitudeDelta = 0.03f; 
        region.span.latitudeDelta = 0.03f;
        [mapView setRegion:region animated:YES]; 
        [mapView setDelegate:self];
        mapView.zoomEnabled = YES;
        mapView.scrollEnabled = NO;

these will vary your zoom level,

        region.span.longitudeDelta = 0.03f; 
        region.span.latitudeDelta = 0.03f;