iphone -- 将 MKMapPoint 距离转换为米

Question

假设我有一个由四个 CLLocationCooperative2D 点组成的正方形，这些点的单位为经纬度，我想找到该正方形的面积(以米为单位)。我将 CLLocationCooperative2D 点转换为 MKMapPoints，然后找到 X-Y 空间中的区域。但是，我找到的面积是以 MKMapPoint 为单位的，它不能直接转换为米。如何将 MKMapPoint 空间中的该区域转换回米？

Answer 1

MapKit 函数 MKMetersBetweenMapPoints 使这变得更容易。

例如，如果你想获取当前显示区域的面积:

MKMapPoint mpTopLeft = mapView.visibleMapRect.origin;

MKMapPoint mpTopRight = MKMapPointMake(
    mapView.visibleMapRect.origin.x + mapView.visibleMapRect.size.width, 
    mapView.visibleMapRect.origin.y);

MKMapPoint mpBottomRight = MKMapPointMake(
    mapView.visibleMapRect.origin.x + mapView.visibleMapRect.size.width, 
    mapView.visibleMapRect.origin.y + mapView.visibleMapRect.size.height);

CLLocationDistance hDist = MKMetersBetweenMapPoints(mpTopLeft, mpTopRight);
CLLocationDistance vDist = MKMetersBetweenMapPoints(mpTopRight, mpBottomRight);

double vmrArea = hDist * vDist;

文档指出该函数“考虑了地球的曲率。”