使用指南针指向实际坐标位置，而不仅仅是北

Posted 2023-04-14

【中文标题】使用指南针指向实际坐标位置，而不仅仅是北

【英文标题】：Using Compass to point to actual coordinate location instead of just North

【发布时间】：2011-07-05 22:51:19

【问题描述】：

我已经看到了一些这样的例子，但不确定如何实现它，（例如iPhone Compass GPS Direction）我需要在 (void)startup 中调用 calcBearingWithLatitude 吗？

我要做的就是让指南针从记忆中拉出一个点，然后将该点用作它的“北方”，可以这么说并指向它，不需要距离或类似的东西。

我的实现文件现在看起来像

@implementation TrackerViewController

@synthesize locationManager; 
@synthesize compass; 
@synthesize headingLabel;

- (void)viewWillAppear:(BOOL)animated 
[super viewWillAppear:animated];

if ([CLLocationManager headingAvailable]) 

 else 
    [[[[UIAlertView alloc] initWithTitle:@"Error" 
                                 message:@"Device doesn't support heading updates" 
                                delegate:nil 
                       cancelButtonTitle:@"OK" 
                       otherButtonTitles:nil] autorelease] show];   



- (void)locationManager:(CLLocationManager *)manager didUpdateHeading:(CLHeading *)newHeading 
double heading = [newHeading magneticHeading] * M_PI / 180.0;
self.compass.transform = CGAffineTransformMakeRotation(-heading);
self.headingLabel.text = [NSString stringWithFormat:@"%d°", (int)[newHeading magneticHeading]];
NSLog(@"%d", (int)[newHeading magneticHeading]);



- (void)locationManager:(CLLocationManager *)manager 
   didFailWithError:(NSError *)error 

//  NSLog(@"Error!");

if (error.code == kCLErrorDenied) 
    [[[[UIAlertView alloc] initWithTitle:@"Error" 
                                 message:@"User didn't allow heading updates" 
                                delegate:nil 
                       cancelButtonTitle:@"OK" 
                       otherButtonTitles:nil] autorelease] show];
    [self.locationManager stopUpdatingHeading];



 - (void)viewDidLoad 
 locationManager=[[CLLocationManager alloc] init];
 locationManager.desiredAccuracy = kCLLocationAccuracyBest;
 locationManager.delegate=self;
 //Start the compass updates.
 [locationManager startUpdatingHeading];
 [super viewDidLoad];
 

- (void)didReceiveMemoryWarning 
// Releases the view if it doesn't have a superview.
[super didReceiveMemoryWarning];

// Release any cached data, images, etc that aren't in use.


- (void)dealloc 
self.locationManager = nil;
self.compass = nil;
self.headingLabel = nil;
[super dealloc];


@end

【问题讨论】：

你能为指南针创建一个自定义标题吗？

【参考方案1】：

我会找到从坐标 A 到坐标 B 的方位，然后使用该方位作为罗盘方位从坐标 A 到坐标 B 的偏移量。

这里有两个链接可以找到坐标的方位

Calculating bearing between two CLLocationCoordinate2Ds

http://shawnsbits.com/blog/2011/07/07/calculating-heading-with-corelocation/

如果您希望罗盘方位在您移动时更新，使其始终指向坐标 B，那么您可能需要在获得新方位或位置时重新计算。