iOS Compass App : Location coordinates keeps changing. How to stabilitse it? - ios

Question

I have just completed compass app which will show distance between 2 coordinates.
Here is working code :
....
// created a timer to call locationUpdate method : 5sec
[NSTimer scheduledTimerWithTimeInterval:5 target: self selector: #selector(locationUpdate) userInfo: nil repeats: YES];
....
-(void)locationUpdate {
[locationManager startUpdatingLocation];
}
-(void)locationManager:(CLLocationManager *)manager
didUpdateToLocation:(CLLocation *)newLoc
fromLocation:(CLLocation *)oldLoc
{
//To get the current location Latitude & Longitude.
float latitude = locationManager.location.coordinate.latitude;
float longitude = locationManager.location.coordinate.longitude;
startPoint = [[CLLocation alloc] initWithLatitude: latitude longitude: longitude ]; //Current Latitude and Longitude
endPoint = [[CLLocation alloc] initWithLatitude: 12.923670 longitude: 77.573496]; //Target Latitude and Longitude -----------------------------------> Need to come from database.
//To get the distance from the 2 coordinates in feet
CLLocationDistance distInMeter = [startPoint distanceFromLocation:endPoint];
//Lable veiw to update remaining distance.
if(distInMeter > 999.000f) {
self.labelLongLat.text = [NSString stringWithFormat: #"Remainig distance %.2f KM with Lat : %lf LAN %lf", distInMeter / 1000, latitude, longitude ];
}else
self.labelLongLat.text = [NSString stringWithFormat: #"Remainig distance %.2f M Lat : %lf LAN %lf" , distInMeter, latitude,longitude ];
}
My problem is while updating location for each 5sec, the coordinates varies a lot. That will result in Remaining distance calculation. Which is highly unstable!! How can I fix this?
Thanks in Advance,

Answer 1

The delegate method you are using is deprecated. You should use locationManager:didUpdateLocations:
- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
{
CLLocation *currentLocation = [locations lastObject];
endPoint = [[CLLocation alloc] initWithLatitude: 12.923670 longitude: 77.573496]; //Target Latitude and Longitude -----------------------------------> Need to come from database.
//To get the distance from the 2 coordinates in meters
CLLocationDistance distInMeter = [currentLocation distanceFromLocation:endPoint];
//Label view to update remaining distance.
if(distInMeter > 999 ) {
self.labelLongLat.text = [NSString stringWithFormat: #"Remaining distance %.2f Km with Lat : %lf LAN %lf", distInMeter / 1000, currentLocation.coordinate.latitude, currentLocation.coordinate.longitude ];
} else {
self.labelLongLat.text = [NSString stringWithFormat: #"Remaining distance %.2f m Lat : %lf LAN %lf" , distInMeter, currentLocation.coordinate.latitude, currentLocation.coordinate.longitude ];
}
}
The accuracy of your location can be affected by signal quality (tall buildings, indoor location etc). You can examine the horizontalAccuracy property of your location to see how accurate the position is. If the accuracy is low then you can defer updating your label. Beware that you may never get an accurate fix.
One strategy is to wait for an accuracy <20m or after 5 updates -
#property (nonatomic) NSInteger locationUpdates;
- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
{
self.locationUpdates++;
CLLocation *currentLocation = [locations lastObject];
if (currentLocation.horizontalAccuracy < 20.0 || self.locationUpdates>5) {
endPoint = [[CLLocation alloc] initWithLatitude: 12.923670 longitude: 77.573496]; //Target Latitude and Longitude -----------------------------------> Need to come from database.
//To get the distance from the 2 coordinates in meters
CLLocationDistance distInMeter = [currentLocation distanceFromLocation:endPoint];
//Label view to update remaining distance.
if(distInMeter > 999 ) {
self.labelLongLat.text = [NSString stringWithFormat: #"Remaining distance %.2f Km with Lat : %lf LAN %lf", distInMeter / 1000, currentLocation.coordinate.latitude, currentLocation.coordinate.longitude ];
} else {
self.labelLongLat.text = [NSString stringWithFormat: #"Remaining distance %.2f m Lat : %lf LAN %lf" , distInMeter, currentLocation.coordinate.latitude, currentLocation.coordinate.longitude ];
}
}
}