iOS6 中的 MapView 在北纬 75 度时不会显示某些缩放级别

iOS6中MapView在北纬>75度时不显示某些缩放级别

swift
import UIKit
import MapKit
class ViewController: UIViewController, MKMapViewDelegate {
    @IBOutlet weak var mapView: MKMapView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        mapView.delegate = self
        
        // 设置地图的中心和显示区域
        let centerCoordinate = CLLocationCoordinate2D(latitude: 80, longitude: 0)
        let span = MKCoordinateSpan(latitudeDelta: 10, longitudeDelta: 10)
        let region = MKCoordinateRegion(center: centerCoordinate, span: span)
        mapView.setRegion(region, animated: true)
    }
    
    // 标记地图上的某个位置
    func addAnnotation() {
        let annotation = MKPointAnnotation()
        annotation.coordinate = CLLocationCoordinate2D(latitude: 80, longitude: 0)
        annotation.title = "北极"
        mapView.addAnnotation(annotation)
    }
    
    // MARK: - MKMapViewDelegate
    
    func mapView(_ mapView: MKMapView, viewFor annotation: MKAnnotation) -> MKAnnotationView? {
        let pinView = MKPinAnnotationView(annotation: annotation, reuseIdentifier: "pin")
        pinView.animatesDrop = true
        return pinView
    }
}