didUpdateToLocation called multiple times - iphone

Question

I have an application in which user track his/her route when jogging or cycling, So i need perfect location, so user's routes will be perfect.
But, I have one problem in this,
locManager = [[CLLocationManager alloc] init];
[locManager setDesiredAccuracy:kCLLocationAccuracyBestForNavigation];
[locManager setDelegate:self];
[locManager startUpdatingLocation];
In viewDidLoad. Using this didUpdateToLocation method called multiple times when I just dont move device a little and on map very strange route draw.
I just cant understand why this happen, if I am doing some wrong or missing something.
Thanks.......

Answer 1

I use locationManager.distanceFilter = 500; (or so) // meters
to prevent multiple calls from happening. just remember to call this BEFORE you start updating your location

Answer 2

You can set the distancefilter of the location manager hope this may help you
locationManager=[[CLLocationManager alloc] init];
locationManager.delegate=self;
locationManager.desiredAccuracy=kCLLocationAccuracyNearestTenMeters;
locationManager.distanceFilter=10.0;
[locationManager startUpdatingLocation];

Answer 3

When you first start location services, you'll generally see multiple location updates come whether you're moving or not. If you examine the horizontalAccuracy of the locations as they come in, you'll see that while it's "warming" up it will show a series of locations with greater and greater accuracy (i.e. smaller and smaller horizontalAccuracy values) until it reaches quiescence.
You could disregard those initial locations until horizontalAccuracy falls below a certain value. Or, better, during start up, you could disregard the previous location if (a) the distance between a new location and the old location is less than the horizontalAccuracy of the old location and (b) if the horizontalAccuracy of the new location is less than that of the prior location.
For example, let's assume you're maintaining an array of CLLocation objects, as well as a reference to the last drawn path:
#property (nonatomic, strong) NSMutableArray *locations;
#property (nonatomic, weak) id<MKOverlay> pathOverlay;
Furthermore, let's assume your location update routine is just adding to the array of locations and then indicating that the path should be redrawn:
- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
{
NSLog(#"%s", __FUNCTION__);
CLLocation* location = [locations lastObject];
[self.locations addObject:location];
[self addPathToMapView:self.mapView];
}
Then the addPathToMapView can therefore remove the second from last location if it's less accurate than the last one and if the distance between them is less than the most recent location's accuracy.
- (void)addPathToMapView:(MKMapView *)mapView
{
NSInteger count = [self.locations count];
// let's see if we should remove the penultimate location
if (count > 2)
{
CLLocation *lastLocation = [self.locations lastObject];
CLLocation *previousLocation = self.locations[count - 2];
// if the very last location is more accurate than the previous one
// and if distance between the two of them is less than the accuracy,
// then remove that `previousLocation` (and update our count, appropriately)
if (lastLocation.horizontalAccuracy < previousLocation.horizontalAccuracy &&
[lastLocation distanceFromLocation:previousLocation] < lastLocation.horizontalAccuracy)
{
[self.locations removeObjectAtIndex:(count - 2)];
count--;
}
}
// now let's build our array of coordinates for our MKPolyline
CLLocationCoordinate2D coordinates[count];
NSInteger numberOfCoordinates = 0;
for (CLLocation *location in self.locations)
{
coordinates[numberOfCoordinates++] = location.coordinate;
}
// if there is a path to add to our map, do so
MKPolyline *polyLine = nil;
if (numberOfCoordinates > 1)
{
polyLine = [MKPolyline polylineWithCoordinates:coordinates count:numberOfCoordinates];
[mapView addOverlay:polyLine];
}
// if there was a previous path drawn, remove it
if (self.pathOverlay)
[mapView removeOverlay:self.pathOverlay];
// save the current path
self.pathOverlay = polyLine;
}
Bottom line, just get rid of locations that are less accurate than the next one you have. You could get even more aggressive in the pruning process if you want, but there are tradeoffs there, but hopefully this illustrates the idea.

Answer 4

startUpdatingLocation
Will continuously update a user's location even when the location does not change. You just need to structure your app to handle these continuous updates according to your needs.
Try reading Apple's documentation on this subject. It is confusing at first but try anyway.
http://developer.apple.com/library/ios/#documentation/UserExperience/Conceptual/LocationAwarenessPG/CoreLocation/CoreLocation.html#//apple_ref/doc/uid/TP40009497-CH2-SW1

Answer 5

I think this is what you need.startMonitoringForRegion:desiredAccuracy
for Example see the following github link.

Answer 6

Try this Bread Crumb sample code provided by Apple..
http://developer.apple.com/library/ios/#samplecode/Breadcrumb/Introduction/Intro.html

Answer 7

Add this,
[locManager stopUpdatingLocation];
into your updateUserLocation delegate method.
Review the following code snippet:
-(void)mapView:(MKMapView *)mapView didUpdateUserLocation:(MKUserLocation *)userLocation
{
[_locationManager stopUpdatingLocation];
}

Answer 8

locationManager.startUpdatingLocation() fetch location continuously and didUpdateLocations method calls several times,
Just set the value for locationManager.distanceFilter value before calling locationManager.startUpdatingLocation().
As I set 200 working fine
locationManager.distanceFilter = 200
locationManager.startUpdatingLocation()