我想根据距离和时间获取位置纬度和经度

Question

在我的项目中，我每 5 秒成功获取一次纬度和经度，并且我正在数据库中保存，但我想要每 5 秒和每 30 米距离的位置数据......

这是我在viewController.m中的代码

 //When I click button this method called...
- (IBAction)getLocationDetails:(UIButton *)sender {
[self CurrentLocationIdentifier];
timer = [NSTimer scheduledTimerWithTimeInterval:5.0f
                                         target:self
                                       selector:@selector(CurrentLocationIdentifier)
                                       userInfo:nil
                                        repeats:YES];
}
-(void)CurrentLocationIdentifier {
//---- For getting current gps location
locationManager = [[CLLocationManager alloc]init];
locationManager.delegate = self;
locationManager.distanceFilter = kCLDistanceFilterNone;
locationManager.desiredAccuracy = kCLLocationAccuracyBest;
[locationManager startUpdatingLocation];
}
- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations {
currentLocation = [locations objectAtIndex:0];
self.longitudeString  = @(currentLocation.coordinate.longitude).stringValue;
self.latitudeString = @(currentLocation.coordinate.latitude).stringValue;    
[locationManager stopUpdatingLocation];
manager.delegate = nil;
NSLog(@"New longitude %@", self.longitudeString);
NSLog(@"New latitude %@", self.latitudeString);
dispatch_async(dispatch_get_main_queue(), ^{

CLGeocoder *geocoder = [[CLGeocoder alloc] init] ;
[geocoder reverseGeocodeLocation:currentLocation completionHandler:^(NSArray *placemarks, NSError *error)
 {
     NSString *CountryArea;
     if (!(error))
     {
         CLPlacemark *placemark = [placemarks objectAtIndex:0];
         NSLog(@"nCurrent Location Detected.......n");
//             NSLog(@"placemark : %@",placemark);
         NSString *locatedAt = [[placemark.addressDictionary valueForKey:@"FormattedAddressLines"] componentsJoinedByString:@", "];
         NSString *address = [[NSString alloc]initWithString:locatedAt];
         NSLog(@"Address : %@", address);
         self.addressString = [[NSString alloc]initWithString:address];
[self saveData];
}
     else
     {
         NSLog(@"Geocode failed with error %@", error);
         NSLog(@"nCurrent Location Not Detectedn");
         //return;
         CountryArea = NULL;
     }
}];

});
// Here is the distance calculation...
CLLocation *startLocation = [[CLLocation alloc] initWithLatitude:currentLocation.coordinate.latitude longitude:currentLocation.coordinate.longitude];
CLLocation *endLocation = [[CLLocation alloc] initWithLatitude:currentLocation.coordinate.latitude longitude:currentLocation.coordinate.longitude];
CLLocationDistance distance = [startLocation distanceFromLocation:endLocation];
if (distance == 0) {
    NSLog(@"Distance.... %f", distance);
}

}

- (void)saveData {
NSManagedObject * managedObj = [[NSManagedObject alloc]initWithEntity:self.GPSDatabaseED insertIntoManagedObjectContext:self.ad.managedObjectContext];
[managedObj setValue:self.longitudeString forKey:@"longitude"];
[managedObj setValue:self.latitudeString forKey:@"latitude"];
[managedObj setValue:self.addressString forKey:@"address"];
[managedObj setValue:self.UDIDString forKey:@"udid"];

NSError * errorObj;
[self.ad.managedObjectContext save:&errorObj];

if (errorObj) {
    NSLog(@"Something goes wrong");
}else
{
    NSLog(@"Saved Successfully");
}

}

Answer 1

这是一个可能的解决方案：

您需要找到最小和最大纬度，经度值以创建NSPredicate。

1. 将度数转换为弧度

   -(float)deg2rad:(float)degrees{
         return degrees * M_PI / 180;
   }
   

2. 查找最小和最大纬度，经度值//距离值(以KM为单位((30米(

   float searchDistance = 0.03;
   float minLat = userLocation.coordinate.latitude - (searchDistance / 69);
   float maxLat = userLocation.coordinate.latitude + (searchDistance / 69);
   float minLon = userLocation.coordinate.latitude - searchDistance / fabs(cos([self deg2rad:userLocation.coordinate.latitude])*69);
   float maxLon = userLocation.coordinate.longitude + searchDistance / fabs(cos([self deg2rad:userLocation.coordinate.latitude])*69);
   

3. 创建谓词如下

   NSPredicate *predicate = [NSPredicate predicateWithFormat:@"latitude <= %f AND latitude >= %f AND longitude <= %f AND longitude >= %f", maxLat, minLat, maxLon, minLon];
   

这将在userLocation周围创建一个正方形，可能会对您有所帮助。