Map View Zoom out with all Annotaion pin...

-(void)zoomToFitMapAnnotations:(MKMapView*)mapView

{

    if([mapView.annotations count] == 0)

        return;

    

    BOOL testing=NO;

    CLLocationCoordinate2D topLeftCoord;

    topLeftCoord.latitude = -90;

    topLeftCoord.longitude = 180;

    

    CLLocationCoordinate2D bottomRightCoord;

    bottomRightCoord.latitude = 90;

    bottomRightCoord.longitude = -180;

    

    if (!testing) {

        

    

    for(VenueAnnotation* annotation in mapView.annotations)

    {

        testing=YES;

        topLeftCoord.longitude = fmin(topLeftCoord.longitude, annotation.coordinate.longitude);

        topLeftCoord.latitude = fmax(topLeftCoord.latitude, annotation.coordinate.latitude);

        

        bottomRightCoord.longitude = fmax(bottomRightCoord.longitude, annotation.coordinate.longitude);

        bottomRightCoord.latitude = fmin(bottomRightCoord.latitude, annotation.coordinate.latitude);

    }

    }

    

    MKCoordinateRegion region;

    region.center.latitude = topLeftCoord.latitude - (topLeftCoord.latitude - bottomRightCoord.latitude) * 0.5;

    region.center.longitude = topLeftCoord.longitude + (bottomRightCoord.longitude - topLeftCoord.longitude) * 0.5;

    region.span.latitudeDelta = fabs(topLeftCoord.latitude - bottomRightCoord.latitude) * 1.1; // Add a little extra space on the sides

    region.span.longitudeDelta = fabs(bottomRightCoord.longitude - topLeftCoord.longitude) * 1.1; // Add a little extra space on the sides

    

    region = [mapView regionThatFits:region];

    [self.mapView setRegion:region animated:YES];

}