How to find the radius of the visible visible area of ​​the MKMapView screen?

Question

I want to know the radius of the visible area on the iphone screen, since I will zoom in and out the visible area, so I want to know the radius of this specific area, how can I do this?

Answer 1

No radius radius required.

You need to use the region parameter from mapView.

Check out apple docs, it's pretty clear from them.

Go through this tutorial. This will help you a lot.

demo for icode blog

in particular, you need to install something like this.

MKCoordinateSpan span = [self coordinateSpanWithMapView:self centerCoordinate:centerCoordinate andZoomLevel:zoomLevel]; MKCoordinateRegion region = MKCoordinateRegionMake(centerCoordinate, span); [self setRegion:region animated:animated]; 

where span can be calculated as

 - (MKCoordinateSpan)coordinateSpanWithMapView:(MKMapView *)mapView centerCoordinate:(CLLocationCoordinate2D)centerCoordinate andZoomLevel:(NSUInteger)zoomLevel { // convert center coordiate to pixel space double centerPixelX = [self longitudeToPixelSpaceX:centerCoordinate.longitude]; double centerPixelY = [self latitudeToPixelSpaceY:centerCoordinate.latitude]; // determine the scale value from the zoom level NSInteger zoomExponent = 20 - zoomLevel; double zoomScale = pow(2, zoomExponent); // scale the map's size in pixel space CGSize mapSizeInPixels = mapView.bounds.size; double scaledMapWidth = mapSizeInPixels.width * zoomScale; double scaledMapHeight = mapSizeInPixels.height * zoomScale; // figure out the position of the top-left pixel double topLeftPixelX = centerPixelX - (scaledMapWidth / 2); double topLeftPixelY = centerPixelY - (scaledMapHeight / 2); // find delta between left and right longitudes CLLocationDegrees minLng = [self pixelSpaceXToLongitude:topLeftPixelX]; CLLocationDegrees maxLng = [self pixelSpaceXToLongitude:topLeftPixelX + scaledMapWidth]; CLLocationDegrees longitudeDelta = maxLng - minLng; // find delta between top and bottom latitudes CLLocationDegrees minLat = [self pixelSpaceYToLatitude:topLeftPixelY]; CLLocationDegrees maxLat = [self pixelSpaceYToLatitude:topLeftPixelY + scaledMapHeight]; CLLocationDegrees latitudeDelta = -1 * (maxLat - minLat); // create and return the lat/lng span MKCoordinateSpan span = MKCoordinateSpanMake(latitudeDelta, longitudeDelta); return span; } 

Greetings :)

Answer 2

Perhaps I do not understand the question, but not so simple:

 - (void)mapView:(MKMapView *)mapView regionDidChangeAnimated:(BOOL)animated { CGFloat latD = mapView.region.span.latitudeDelta; CGFloat lngD = mapView.region.span.longitudeDelta; NSLog(@"This is the latitude delta of the visible map: %f", latD); NSLog(@"This is the longitude delta of the visible map: %f", lngD); } 

Answer 3

I'm stuck in a problem

I drew a shape in the form of a map and even got the center coordinate. It remains to find the radius from the central coordinate.

if anyone can help me.

[This is the shape I drew, the annotation is the center point, you need to find the radius and then draw a circle on it]

https://i.stack.imgur.com/iVUpA.png