显示特定位置的 iPhone 罗盘

Question

我是 objective-c 的新手，所以如果我的问题太垃圾，我想道歉。

我正在编写一个指南针，但它正在运行(感谢教程)。给出了实际位置(经度和纬度)。我的指南针内的箭头是否可以向我显示特定位置(经度 2 和纬度 2)的方向？我读到我必须考虑 iphone 的磁性和真实航向。

Answer 1

- (void)locationManager:(CLLocationManager *)manager didUpdateHeading:(CLHeading *)newHeading {
    double heading = newHeading.trueHeading; //in degree relative to true north
    double bearing = ... //get current bearing in degree relative to true north
                         //with the JS library mentioned below it would be something like
                         //bearing = userLoc.bearingTo(destionation);

    //just two lines, the the sake of the example
    double rotationInDegree = (bearing - heading);  //the important line
    rotationInDegree = fmod((rotationInDegree + 360), 360);  //just to be on the safe side :-)
    compassViewPerhapsAsImage.transform=CGAffineTransformMakeRotation(DegreesToRadians(rotationInDegree));
}

计算方位的好链接:

• http://www.movable-type.co.uk/scripts/latlong.html带有说明和 Javascript 示例，但非常容易转换! :-)
• https://github.com/tadelv/CLLocation-Bearing作为 Objective C 项目