Updating user location using iPhone GPS without internet - iphone

Question

I need to get user location and fetch latitude and longitude of even when there is no internet available.
Right now i have implemented CoreLocation methods:-
-(void)updatestart
{
// Current location
_locationManager = [[CLLocationManager alloc]init];
_locationManager.desiredAccuracy = kCLLocationAccuracyBest;
_locationManager.delegate = self;
[_locationManager startUpdatingLocation];
}
- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error
{
NSLog(#"didFailWithError: %#", error);
UIAlertView *errorAlert = [[UIAlertView alloc]
initWithTitle:#"Error" message:#"Failed to Get Your Location" delegate:nil cancelButtonTitle:#"OK" otherButtonTitles:nil];
[errorAlert show];
}
- (void)locationManager:(CLLocationManager *)manager
didUpdateToLocation:(CLLocation *)newLocation
fromLocation:(CLLocation *)oldLocation{
[_locationManager stopUpdatingLocation];
NSLog(#"%f",_locationManager.location.coordinate.latitude);
NSLog(#"%f",_locationManager.location.coordinate.longitude);
}
and i am getting the location updates but this only works if we have internet connection.
I guess using iPhone GPS we can fetch the location even without internet.
Any idea of how to implement that??
Thanks in advance.

Answer 1

GPS doesn't need data exchange using internet, but it has basically 2 disadvantages:
it takes a long time to get position if you haven't used it recently (this is
due to satellite search)
it doesn't work inside buildings or where streets are too small
between buildings (this happens a lot in Italy)
Another way that it doesn't need data exchange is location based on cell tower, but of course your device should have cellular chip installed.
From your code I see three things that should be fixed as soon as possible.
Sometimes the first location is cached and it doesn't represent the
actual location
It will be better to stop the location manager when you receive a
valid coordinate, that means: not cached, with an horizontal accuracy >=0 and with an horizontal accuracy that match your requirements,
The delegate methods to get location is deprecated (depending on your
deployment target). Here is a little snippet for the first two
points:
-(void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations{
CLLocation * newLocation = [locations lastObject];
if (newLocation.horizontalAccuracy < 0) {
return;
}
NSTimeInterval interval = [newLocation.timestamp timeIntervalSinceNow];
if (abs(interval)>20) {
return;
}
}