#import <CoreLocation/CoreLocation.h>

CLLocationManager *locManager = [[CLLocationManager alloc] init];

locManager.delegate = self;

[locManager startUpdatingLocation]; 

- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations

{ 

 CLLocation *curLocation = [locations lastObject];
  
  if(curLocation.horizontalAccuracy > 0)
  {
    NSLog(@"当前位置：%.0f,%.0f +/- %.0f meters",curLocation.coordinate.longitude,
       curLocation.coordinate.latitude,
       curLocation.horizontalAccuracy);
  }
  
  if(curLocation.verticalAccuracy > 0)
  {
    NSLog(@"当前海拔高度：%.0f +/- %.0f meters",curLocation.altitude,curLocation.verticalAccuracy);
  }

}

- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error
{ //此方法为定位失败的时候调用。并且由于会在失败以后重新定位，所以必须在末尾停止更新 

 if(error.code == kCLErrorLocationUnknown)
  {
    NSLog(@"Currently unable to retrieve location.");
  }
  else if(error.code == kCLErrorNetwork)
  {
    NSLog(@"Network used to retrieve location is unavailable.");
  }
  else if(error.code == kCLErrorDenied)
  {
    NSLog(@"Permission to retrieve location is denied.");
    [manager stopUpdatingLocation];
  }


} 

extern const CLLocationAccuracy kCLLocationAccuracyBestForNavigation;

extern const CLLocationAccuracy kCLLocationAccuracyBest;

extern const CLLocationAccuracy kCLLocationAccuracyNearestTenMeters;

extern const CLLocationAccuracy kCLLocationAccuracyHundredMeters;

extern const CLLocationAccuracy kCLLocationAccuracyKilometer;

extern const CLLocationAccuracy kCLLocationAccuracyThreeKilometers; 

CLLocationManager *locManager = [[CLLocationManager alloc] init];

locManager.delegate = self;

locManager.desiredAccuracy = kCLLocationAccuracyHundredMeters;//定位精度百米以内

locManager.distanceFilter = 200;//水平或者垂直移动200米调用代理更新位置

[locManager startUpdatingLocation];//启动位置更新 

- (BOOL)locationManagerShouldDisplayHeadingCalibration:(CLLocationManager *)manager
{
  return YES;
}

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

- (void)locationManager:(CLLocationManager *)manager didUpdateHeading:(CLHeading *)newHeading
{
  if(newHeading.headingAccuracy >=0)
  {
    NSString *headingDesc = [NSString stringWithFormat:@"%.0f degrees (true), %.0f degrees (magnetic)",newHeading.trueHeading,newHeading.magneticHeading];
    
    NSLog(@"%@",headingDesc);
  }
}

#import "ViewController.h"

#define kDestLongitude 113.12 //精度
#define kDestLatitude 22.23 //纬度
#define kRad2Deg 57.2957795 // 180/π
#define kDeg2Rad 0.0174532925 // π/180

@interface ViewController ()
@property (strong, nonatomic) IBOutlet UILabel *lblMessage;
@property (strong, nonatomic) IBOutlet UIImageView *imgView;
@property (strong, nonatomic) CLLocationManager *locationManager;
@property (strong, nonatomic) CLLocation *recentLocation;

-(double)headingToLocation:(CLLocationCoordinate2D)desired current:(CLLocationCoordinate2D)current;
@end

@implementation ViewController

- (void)viewDidLoad
{
  [super viewDidLoad];

  self.locationManager = [[CLLocationManager alloc] init];
  self.locationManager.delegate = self;
  self.locationManager.desiredAccuracy = kCLLocationAccuracyThreeKilometers;
  self.locationManager.distanceFilter = 1609; //1英里≈1609米
  [self.locationManager startUpdatingLocation];
  
  if([CLLocationManager headingAvailable])
  {
    self.locationManager.headingFilter = 10; //10°
    [self.locationManager startUpdatingHeading];
  }
}

/*
 * According to Movable Type Scripts
 * http://mathforum.org/library/drmath/view/55417.html
 *
 * Javascript:
 *
 * var y = Math.sin(dLon) * Math.cos(lat2);
 * var x = Math.cos(lat1)*Math.sin(lat2) -
 * Math.sin(lat1)*Math.cos(lat2)*Math.cos(dLon);
 * var brng = Math.atan2(y, x).toDeg();
 */
-(double)headingToLocation:(CLLocationCoordinate2D)desired current:(CLLocationCoordinate2D)current
{
  double lat1 = current.latitude*kDeg2Rad;
  double lat2 = desired.latitude*kDeg2Rad;
  double lon1 = current.longitude;
  double lon2 = desired.longitude;
  double dlon = (lon2-lon1)*kDeg2Rad;
  
  double y = sin(dlon)*cos(lat2);
  double x = cos(lat1)*sin(lat2) - sin(lat1)*cos(lat2)*cos(dlon);
  
  double heading=atan2(y,x);
  heading=heading*kRad2Deg;
  heading=heading+360.0;
  heading=fmod(heading,360.0);
  return heading;
}

//处理航向 
- (void)locationManager:(CLLocationManager *)manager didUpdateHeading:(CLHeading *)newHeading
{
  if(self.recentLocation!=nil && newHeading.headingAccuracy>=0)
  {
    CLLocation *destLocation = [[CLLocation alloc] initWithLatitude:kDestLatitude longitude:kDestLongitude];
    
    double course = [self headingToLocation:destLocation.coordinate current:self.recentLocation.coordinate];
    
    double delta = newHeading.trueHeading - course;
    
    if (abs(delta) <= 10)
    {
      self.imgView.image = [UIImage imageNamed:@"up_arrow.png"];
    }
    else
    {
      if (delta > 180)
      {
        self.imgView.image = [UIImage imageNamed:@"right_arrow.png"];
      }
      else if (delta > 0)
      {
        self.imgView.image = [UIImage imageNamed:@"left_arrow.png"];
      }
      else if (delta > -180)
      {
        self.imgView.image = [UIImage imageNamed:@"right_arrow.png"];
      }
      else
      {
        self.imgView.image = [UIImage imageNamed:@"left_arrow.png"];
      }
    }
    self.imgView.hidden = NO;
  }
  else
  {
    self.imgView.hidden = YES;
  }
}

//处理定位成功
- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
{
  CLLocation *curLocation = [locations lastObject];
  
  if(curLocation.horizontalAccuracy >= 0)
  {
    self.recentLocation = curLocation;
    
    CLLocation *destLocation = [[CLLocation alloc] initWithLatitude:kDestLatitude longitude:kDestLongitude];
    
    CLLocationDistance distance = [destLocation distanceFromLocation:curLocation];
    
    if(distance<500)
    {
      [self.locationManager stopUpdatingLocation];
      [self.locationManager stopUpdatingHeading];
      self.lblMessage.text = @"您已经到达目的地!";
    }
    else
    {
      self.lblMessage.text = [NSString stringWithFormat:@"距离目的地还有%f米",distance];
    }
  }
}

//处理定位失败
- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error
{
  if(error.code == kCLErrorLocationUnknown)
  {
    NSLog(@"Currently unable to retrieve location.");
  }
  else if(error.code == kCLErrorNetwork)
  {
    NSLog(@"Network used to retrieve location is unavailable.");
  }
  else if(error.code == kCLErrorDenied)
  {
    NSLog(@"Permission to retrieve location is denied.");
    [self.locationManager stopUpdatingLocation];
    self.locationManager = nil;
  }
}


- (void)didReceiveMemoryWarning
{
  [super didReceiveMemoryWarning];
  // Dispose of any resources that can be recreated.
}

@end