Convert distance on MKMapView to distance for UIView

Question

How do I convert distance (for example 400 meters) on MKMapView to distance for UIView? I want to show MKAnnotationView that depends on current zoom level on MKMapView.

score 10 · Accepted Answer · answered Dec 07 '11 at 08:31

10

First, create a region with 400 meters length:

MKCoordinateRegion myRegion = MKCoordinateRegionMakeWithDistance(mapView.centerCoordinate, 400, 0);

After that use convert region methods for getting real rect:

CGRect myRect = [mapView convertRegion: myRegion toRectToView: nil];
NSLog(@"width for 400m is %f", myRect.size.width);

Hope, this helps.

answered Dec 07 '11 at 08:31

Denis

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if you set the distance as the `latitudinalMeters` attribute for `MKCoordinateRegionMakeWithDistance`, as in your example, you should really read the height not the width of the resulting `CGRect`. See http://developer.apple.com/library/ios/#documentation/MapKit/Reference/MapKitFunctionsReference/Reference/reference.html#//apple_ref/c/func/MKCoordinateRegionMakeWithDistance – Nicu Surdu Nov 01 '12 at 12:39

score 5 · Answer 2 · answered Dec 07 '11 at 08:11

You have several selectors in MKMapView to convert UIView coordinates on the screen to geo coordinates (and geo -> screen as well):

- (CGPoint)convertCoordinate:(CLLocationCoordinate2D)coordinate toPointToView:(UIView *)view
- (CLLocationCoordinate2D)convertPoint:(CGPoint)point toCoordinateFromView:(UIView *)view

I assume 400 meters is a distance between 2 coordinates, so should you have a reference to 2 CLLocationCoordinate2D structures.
Just use - (CGPoint)convertCoordinate:(CLLocationCoordinate2D)coordinate toPointToView:(UIView *)view to get the corresponding CGPoint (= screen coordinates) and you should be then able to calculate the screen distance.

Convert distance on MKMapView to distance for UIView

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