用于计算轴承w / Haversine功能的CLL位类别 [英] CLLocation Category for Calculating Bearing w/ Haversine function

问题描述

我正在尝试为CLLocation编写一个类别，以将轴承返回到另一个CLLocation。

I'm trying to write a category for CLLocation to return the bearing to another CLLocation.

我相信我做错了公式（calculous是不是我强大的西装）。返回的方位总是关闭。

I believe I'm doing something wrong with the formula (calculous is not my strong suit). The returned bearing is always off.

我一直在查看这个问题，并尝试应用所接受的更改作为正确答案及其引用的网页：

I've been looking at this question and tried applying the changes that were accepted as a correct answer and the webpage it references:

计算两个CLLocationCoordinate2D之间的方位

http：/ /www.movable-type.co.uk/scripts/latlong.html

感谢您的任何指示。我已经尝试合并其他问题的反馈，但我仍然没有得到一些东西。

Thanks for any pointers. I've tried incorporating the feedback from that other question and I'm still just not getting something.

谢谢

这是我的类别 -

----- CLLocation + Bearing.h

----- CLLocation+Bearing.h

#import <Foundation/Foundation.h>
#import <CoreLocation/CoreLocation.h>


@interface CLLocation (Bearing)

-(double) bearingToLocation:(CLLocation *) destinationLocation;
-(NSString *) compassOrdinalToLocation:(CLLocation *) nwEndPoint;

@end

--------- CLLocation + Bearing.m

---------CLLocation+Bearing.m

#import "CLLocation+Bearing.h"

double DegreesToRadians(double degrees) {return degrees * M_PI / 180;};
double RadiansToDegrees(double radians) {return radians * 180/M_PI;};


@implementation CLLocation (Bearing)

-(double) bearingToLocation:(CLLocation *) destinationLocation {

 double lat1 = DegreesToRadians(self.coordinate.latitude);
 double lon1 = DegreesToRadians(self.coordinate.longitude);

 double lat2 = DegreesToRadians(destinationLocation.coordinate.latitude);
 double lon2 = DegreesToRadians(destinationLocation.coordinate.longitude);

 double dLon = lon2 - lon1;

 double y = sin(dLon) * cos(lat2);
 double x = cos(lat1) * sin(lat2) - sin(lat1) * cos(lat2) * cos(dLon);
 double radiansBearing = atan2(y, x);

 return RadiansToDegrees(radiansBearing);
}

推荐答案

你的代码对我来说似乎不错。该计算没有错。您没有指定结果的距离，但您可以尝试将您的弧度/度数转换器调整为：

Your code seems fine to me. Nothing wrong with the calculous. You don't specify how far off your results are, but you might try tweaking your radian/degrees converters to this:

double DegreesToRadians(double degrees) {return degrees * M_PI / 180.0;};
double RadiansToDegrees(double radians) {return radians * 180.0/M_PI;};

如果您获得负轴承，请添加 2 * M_PI 到radiansBearing的最终结果（如果在转换为度数后执行，则为360）。 atan2将范围 -M_PI 的结果返回到 M_PI （-180到180度），所以你可能想要使用类似下面的代码将其转换为指南针轴承

If you are getting negative bearings, add 2*M_PI to the final result in radiansBearing (or 360 if you do it after converting to degrees). atan2 returns the result in the range -M_PI to M_PI (-180 to 180 degrees), so you might want to convert it to compass bearings, using something like the following code

if(radiansBearing < 0.0)
    radiansBearing += 2*M_PI;

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