how to find current zoom level of MKMapView? - iphone

Question

I want to know the current zoom level of MKMapView in iphone programming, how can I do that?
Actually I have one app, that is taking few arguments(Radius from center to corner of MKMapView) are returning the store details in that are, when I am on MKMapView, the radius is very high and it changes when Radius is smaller, so I want to know the zoom level and setup my webservice according to that, How can I get zoom level of current MKMapView visible area?

Answer 1

I created very simple helper subclass for it:
#define MERCATOR_RADIUS 85445659.44705395
#define MAX_GOOGLE_LEVELS 20
#interface MKMapView (ZoomLevel)
- (double)getZoomLevel;
#end
#implementation MKMapView (ZoomLevel)
- (double)getZoomLevel
{
CLLocationDegrees longitudeDelta = self.region.span.longitudeDelta;
CGFloat mapWidthInPixels = self.bounds.size.width;
double zoomScale = longitudeDelta * MERCATOR_RADIUS * M_PI / (180.0 * mapWidthInPixels);
double zoomer = MAX_GOOGLE_LEVELS - log2( zoomScale );
if ( zoomer < 0 ) zoomer = 0;
// zoomer = round(zoomer);
return zoomer;
}
#end

Answer 2

You can use span inside the region property of the MKMapView. It is defined like this:
typedef struct {
CLLocationDegrees latitudeDelta;
CLLocationDegrees longitudeDelta;
} MKCoordinateSpan;
Take a look at the documentation. It is well explained there.

Answer 3

The easiest way to get an Integer of the current zoom level, is by using the MapView function: regionDidChangeAnimated. This function recognizes every change in zoom and will give you the basis for the calculation of the zoom factor.
Just insert this function into your MapView class (works for Swift 3.0):
var mapView: MKMapView! = nil
...
func mapView(_ mapView: MKMapView, regionDidChangeAnimated animated: Bool) {
let zoomWidth = mapView.visibleMapRect.size.width
let zoomFactor = Int(log2(zoomWidth)) - 9
print("...REGION DID CHANGE: ZOOM FACTOR \(zoomFactor)")
}
And you will get a zoomFactor value out of it, where 0 is the most near point you can zoom into the map and every higher value is a far far away zoom... :-)

Answer 4

All the previous answers do not take into consideration current map rotation. MKMapView's longitudeDelta differs for non-rotated map and rotated map.
Here is a great function for straight map zoom calculation: https://stackoverflow.com/a/15020534/4923516
And here is my improvement in Swift, that takes into consideration map rotation and returns current zoom level:
class MyMapView : MKMapView {
func getZoom() -> Double {
// function returns current zoom of the map
var angleCamera = self.camera.heading
if angleCamera > 270 {
angleCamera = 360 - angleCamera
} else if angleCamera > 90 {
angleCamera = fabs(angleCamera - 180)
}
let angleRad = M_PI * angleCamera / 180 // camera heading in radians
let width = Double(self.frame.size.width)
let height = Double(self.frame.size.height)
let heightOffset : Double = 20 // the offset (status bar height) which is taken by MapKit into consideration to calculate visible area height
// calculating Longitude span corresponding to normal (non-rotated) width
let spanStraight = width * self.region.span.longitudeDelta / (width * cos(angleRad) + (height - heightOffset) * sin(angleRad))
return log2(360 * ((width / 256) / spanStraight)) + 1;
}
}
You can download sample project in my repo: https://github.com/d-babych/mapkit-wrap

Answer 5

If it helps you can also use mapView.camera.altitude to get the current altitude of the currently displayed map region.
This is what helped me when I searched how to get the map zoom level.