让ios中MKMapView的定位点不居中的方法

CLLocationCoordinate2D centerCoordanate;
centerCoordanate.latitude = [userLocation coordinate].latitude - 0.0037;
centerCoordanate.longitude = [userLocation coordinate].longitude;
MKCoordinateRegion reg = MKCoordinateRegionMakeWithDistance(centerCoordanate, 1000, 1000);
[_mapView setRegion:reg animated:YES];