I use this code to show all my annotations on my map:
MKMapRect zoomRect = MKMapRectNull; for (id annotation in mapView.annotat
In my code, I add extra spacing around, so it will automatically adjust the zoom level in order to fit.
[aMapView setVisibleMapRect:zoomRect edgePadding:UIEdgeInsetsMake(-100, -50, -50, -50) animated:YES];