我不能让这种算法权利。我试图做一个指南针指向在某个位置，而不是仅仅指向，让我们说，北部。什么是错的。我花了很多时间试图弄清楚这一点，但我无法找到它。任何想法？

   - （无效）locationManager：（CLLocationManager *）经理didUpdateHeading：（CLHeading *）newHeading {

双distanceEast =（location.longitude大于0＆安培;＆安培; otherLocation.longitude℃的）？ 180  -  location.longitude + otherLocation.longitude  -  -180：otherLocation.longitude  -  location.longitude;

    如果（distanceEast℃，）{
        distanceEast + = 360;
    }

    双distanceWest =（location.longitude＆℃，安培;＆安培; otherLocation.longitude大于0）？ -180  -  location.longitude  -  180  -  otherLocation.longitude：location.longitude  -  otherLocation.longitude;

    如果（distanceWest℃，）{
        distanceWest + = 360;
    }

    浮动latitudinalDifference =（otherLocation.latitude  -  location.latitude）;
    浮longitudinalDifference = FMIN（distanceEast，distanceWest）;

    浮ARCTAN = ATAN（longitudinalDifference / latitudinalDifference）;

        浮动oldRadian =（-manager.heading.trueHeading * M_PI /180.0f)+arcTan+M_PI;
        浮动newRadian =（-newHeading.trueHeading * M_PI /180.0f)+arcTan+M_PI;

        CABasicAnimation *动画;
        动画= [CABasicAnimation animationWithKeyPath：@transform.rotation];
        animation.fromValue = [NSNumber的numberWithFloat：oldRadian]。
        animation.toValue = [NSNumber的numberWithFloat：newRadian]。
        animation.duration = 0.5F;
        directionsArrow.layer.anchorPoint = CGPointMake（0.5，0.5）;

        [directionsArrow.layer addAnimation：动画forKey：@rotationCompass];
        directionsArrow.transform = CGAffineTransformMakeRotation（newRadian）;
}
 

解决方案

 双LON = location.longitude  -  otherLocation.longitude;
双Y = SIN（LON）* COS（otherLocation.latitude）;
双X = COS（location.latitude）*罪（otherLocation.latitude） - 罪（location.latitude）* COS（otherLocation.latitude）* COS（LON）;
双角= ATAN2（Y，X）;
 

角度是两个位置之间的方位。

I can't get this algorithm right. I'm trying to make a compass that points at a certain location instead of just pointing to, let's say, north. Something is wrong. I've spent a lot of time trying to figure this out, but i just can't find it. Any ideas?

- (void)locationManager:(CLLocationManager *)manager didUpdateHeading:(CLHeading *)newHeading{

double distanceEast = (location.longitude > 0 && otherLocation.longitude < 0) ? 180 - location.longitude + otherLocation.longitude - -180: otherLocation.longitude - location.longitude;

    if (distanceEast < 0) {
        distanceEast += 360;
    }

    double distanceWest = (location.longitude < 0 && otherLocation.longitude > 0) ? -180 - location.longitude - 180 - otherLocation.longitude : location.longitude - otherLocation.longitude;

    if (distanceWest < 0) {
        distanceWest += 360;
    }

    float latitudinalDifference = (otherLocation.latitude - location.latitude);
    float longitudinalDifference = fmin(distanceEast,distanceWest);

    float arcTan = atan(longitudinalDifference / latitudinalDifference);

        float oldRadian = (-manager.heading.trueHeading *M_PI /180.0f)+arcTan+M_PI;
        float newRadian = (-newHeading.trueHeading *M_PI /180.0f)+arcTan+M_PI;

        CABasicAnimation *animation;
        animation=[CABasicAnimation animationWithKeyPath:@"transform.rotation"];
        animation.fromValue = [NSNumber numberWithFloat:oldRadian];
        animation.toValue = [NSNumber numberWithFloat:newRadian];
        animation.duration = 0.5f;
        directionsArrow.layer.anchorPoint = CGPointMake(0.5, 0.5);

        [directionsArrow.layer addAnimation:animation forKey:@"rotationCompass"];
        directionsArrow.transform = CGAffineTransformMakeRotation(newRadian);
}

double lon = location.longitude - otherLocation.longitude;
double y = sin(lon) * cos(otherLocation.latitude);
double x = cos(location.latitude) * sin(otherLocation.latitude) - sin(location.latitude) * cos(otherLocation.latitude) * cos(lon);
double angle = atan2(y, x);

angle is the bearing between the two locations.