MKMapView how to know rotation angle?

Question

In iOS 7, an MKMapView can be rotated by the user (like in the Maps app).

I have overlays and to determine whether I can display them, I need to compute the zoom scale. In iOS 6, I used to do:

MKZoomScale zoomScale = self.mapView.bounds.size.width / self.mapView.visibleMapRect.size.width;

The problem is that the result of this computation changes when the user rotates the map, where as the actual zoom scale should be the same (the size of the overlays tiles is the same, it's just rotated).

So my problem is the following: how to compute the real zoom scale that does not change when the user rotates the map ? If I had the rotation angle, I could correct the "bias" but I could not find any property in MKMapView to have this angle.

A workaround would be to disable map rotation, but I want to keep this feature.

Thanks in advance.

nevan king nevan king · Accepted Answer · 2013-10-11T15:22:21

Instead of using a computed zoom scale, you can use the new MKMapCamera altitude property. It won't change as the map rotates and I think it stays the same even if the user changes the map's pitch angle.

MKMapCamera *camera = self.mapView.camera;
CLLocationDistance altitude = camera.altitude;
if (altitude < 3000 && altitude > 1000) {
    // do something
}

If you still need to know the rotation angle, you can get that from the map camera too:

CLLocationDirection mapAngle = camera.heading;

MKMapView how to know rotation angle?

1 Answers