iOS根据两点经纬度坐标计算指南针方位角

#import <CoreLocation/CoreLocation.h>

+ (double)ca_getCompassAngleFromCoor1:(CLLocationCoordinate2D)coor1 coor2:(CLLocationCoordinate2D)coor2 {
    double long1 = coor1.longitude;
    double lat1 = coor1.latitude;
    double long2 = coor2.longitude;
    double lat2 = coor2.latitude;
         
    double φ1 = [CLLocation toRadius:lat1];
    double φ2 = [CLLocation toRadius:lat2];
    double Δλ = [CLLocation toRadius:(long2 - long1)];
    
    double x = cos(φ1) * sin(φ2) - sin(φ1) * cos(φ2) * cos(Δλ);
    double y = sin(Δλ) * cos(φ2);
    double θ = atan2(y, x);
    
    double bearing = [CLLocation toDegrees:θ];
    return bearing;
}

+ (double)toDegrees:(double)radius {
    return radius * 180.0 / M_PI;
}

+ (double)toRadius:(double)degree {
    return degree * M_PI / 180.0;
}

double bearing = [CLLocation ca_getCompassAngleFromCoor1:(CLLocationCoordinate2DMake(20, 20)) coor2:(CLLocationCoordinate2DMake(20, 140))];
NSLog(@"bearing:%.2f", bearing);
//设置地图方位角...