swift - 计算 MKMapView 中 MKPolygon 的面积

Question

我只是不知道如何计算 MKMapView 上的面积。有谁解决过这个问题吗？

这是我的代码，但它返回的太多了:

func ringArea() -> Double{
    var area: Double = 0

    if templocations.count > 2 {
        var p1,p2:CLLocationCoordinate2D

        for var i = 0; i < templocations.count - 1; i++ {
            var loc = templocations[i] as CLLocation
            p1 = CLLocationCoordinate2D(latitude: loc.coordinate.latitude, longitude: loc.coordinate.longitude)

            loc = templocations[i+1] as CLLocation
            p2 = CLLocationCoordinate2D(latitude: loc.coordinate.latitude, longitude: loc.coordinate.longitude)

            var sinfunc: Float = (2 + sinf(Float(degreeToRadiant(p1.latitude))) + sinf(Float(degreeToRadiant(p2.latitude))))

            area += degreeToRadiant(p2.longitude - p1.longitude) * Double(sinfunc)
        }
        area = area * kEarthRadius * kEarthRadius / 2;
    }
    return area
}

Answer 1

Stefan 在 Swift 5.0 中的回答:

import MapKit
let kEarthRadius = 6378137.0

func radians(degrees: Double) -> Double {
    return degrees * .pi / 180
}

func regionArea(locations: [CLLocationCoordinate2D]) -> Double {

    guard locations.count > 2 else { return 0 }
    var area = 0.0

    for i in 0..<locations.count {
        let p1 = locations[i > 0 ? i - 1 : locations.count - 1]
        let p2 = locations[i]

        area += radians(degrees: p2.longitude - p1.longitude) * (2 + sin(radians(degrees: p1.latitude)) + sin(radians(degrees: p2.latitude)) )
    }
    area = -(area * kEarthRadius * kEarthRadius / 2)
    return max(area, -area) // In order not to worry about is polygon clockwise or counterclockwise defined.
}