[iOS][Background][CLLocationManager]Bad map accuracy - ios

Question

I am working on an application which aims to display on a map the position of the iPhone during an activity (adding annotations and drawing line between them).
To do this, I use a Location Manager which get new positions and notify the MapDisplayViewController. When using with the simulator I got good results as you can see here http://www.youtube.com/watch?v=ESLIYSU_Mqw but with an iPhone I got weird result such 200 meters wrong.
I also use a MKMapView to display the device position. with these settings (next code block) I got that http://grab.by/mgUU.
If I show the user location I got different results, it is normal ?
- (void)setupMap {
self.mapView.delegate = self;
[self.mapView setUserTrackingMode:MKUserTrackingModeFollow animated:YES];
[self.mapView setUserInteractionEnabled:NO];
[self.mapView setShowsUserLocation:NO];
[self.mapView setZoomEnabled:NO];
[self.waitingView start];
}
Here screenshots with a real device:
background: http://grab.by/mgN2
no background: http://grab.by/mgNc
edit: the difference come froms I used for these 2 cases, 2 different ways of getting current location of the device are used:
the handle from the mapView when the app is active
the handle from the Location Manager when the app is in background
Does it a good idea to mix both locations system ?
I also test this solution CLLocationManager and accuracy issues - any experiences? but I got the same result.
Thanks ;)
Setup of Location Manager:
- (void)setup {
self.locationManager = [CLLocationManager new];
self.locationManager.delegate = self;
self.locationManager.desiredAccuracy = kCLLocationAccuracyBest;
self.isUpdatingLocation = NO;
}
Notification: when adding location in background:
- (void)doUpdateWithLocation:(CLLocation *)location {
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
[self beginBackgroundUpdateTask];
NSLog(#"%s do update in background %#", __PRETTY_FUNCTION__, location);
if (self.userLocationFound == NO && self.isUpdatingLocation == YES) {
self.startCoordinate = CLLocationCoordinate2DMake(location.coordinate.latitude, location.coordinate.longitude);
self.userLocationFound = YES;
}
else if (self.isUpdatingLocation) {
static int distance;
ABGPSPosition *position = [[ABGPSPosition alloc] init];
position.startPoint = MKMapPointForCoordinate(self.startCoordinate);
position.endPoint = MKMapPointForCoordinate(location.coordinate);
//INFO: Get the distance between this new point and the previous point.
CLLocationDistance metersApart = MKMetersBetweenMapPoints(position.startPoint, position.endPoint);
if (metersApart > MINIMUM_DELTA_METERS) {
MKMapPoint points[2] = {position.startPoint, position.endPoint};
distance += metersApart;
NSLog(#"%s - %d", __PRETTY_FUNCTION__, distance);
NSInteger count = [self.measurementArray count];
[self willChange:NSKeyValueChangeInsertion
valuesAtIndexes:[NSIndexSet indexSetWithIndex:count] forKey: #"measurementArray"];
[self.measurementArray insertObject:location atIndex:count];
[self didChange:NSKeyValueChangeInsertion
valuesAtIndexes:[NSIndexSet indexSetWithIndex:count] forKey: #"measurementArray"];
self.startCoordinate = CLLocationCoordinate2DMake(location.coordinate.latitude, location.coordinate.longitude);
}
}
[self endBackgroundUpdateTask];
});
}
MapDisplayViewController get the new location:
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
if ([keyPath isEqualToString:keyPathMeasurementArray]) {
if ([change[NSKeyValueChangeKindKey] intValue] == NSKeyValueChangeInsertion) {
NSIndexSet *insertedIndexSet = change[NSKeyValueChangeIndexesKey];
[insertedIndexSet enumerateIndexesUsingBlock:^(NSUInteger idx, BOOL *stop) {
CLLocation *location = self.locationManager.measurementArray[idx];
MKUserLocation *userLocation = [[MKUserLocation alloc] init];
[userLocation setCoordinate:location.coordinate];
NSLog(#"%s - didUpdateUserLocation", __PRETTY_FUNCTION__);
[self.locationBackgroundList addObject:userLocation];
NSLog(#"%s | %#", __PRETTY_FUNCTION__, self.locationBackgroundList);
}];
}
}
else {
[super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
}
}
MapDisplayViewController adding Annotation the new map view:
- (void)handleAddLocations {
NSLog(#"%s | %#", __PRETTY_FUNCTION__, self.locationBackgroundList);
if ([self.locationBackgroundList count] > 0) {
for (MKUserLocation *backgroundUserLocation in self.locationBackgroundList) {
{
LocAnnotation* annotation = [[LocAnnotation alloc] initWithCoordinate:backgroundUserLocation.coordinate];
NSLog(#"%s %#", __PRETTY_FUNCTION__, [backgroundUserLocation description]);
[self.mapView addAnnotation:annotation];
}
[self mapView:self.mapView didUpdateUserLocation:backgroundUserLocation];
}
NSString *message = [NSString stringWithFormat:#"%s | Annotation number: %d", __PRETTY_FUNCTION__, [self.locationBackgroundList count]];
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"Debug" message:message delegate:self cancelButtonTitle:#"Cancel" otherButtonTitles:#"OK", nil];
[alert show];
[self.locationBackgroundList removeAllObjects];
self.locationBackgroundList = [[NSMutableArray alloc] init];
}
}

Answer 1

Fixed you have to use only one way to locate your device with the CLLocationManager or the MapView. ;)