MKMapRectMake缩放

MKMapRectMake标记东北和西南显示区域。

我能否设置之后将地图缩放一点？

routeRect = MKMapRectMake(southWestPoint.x, southWestPoint.y, northEastPoint.x - southWestPoint.x, northEastPoint.y - southWestPoint.y);
[self.mapView setVisibleMapRect:routeRect];

应该如何对地图进行缩放？

MKCoordinateRegion region = MKCoordinateRegionForMapRect(routeRect);
MKCoordinateSpan span;
span.latitudeDelta = 0.09;
span.longitudeDelta = 0.09;
region.span = span;
region = [self.mapView regionThatFits:region];
[_mapView setRegion:region animated:YES];