Question

I am making an application which tracks the user. I have notice when the application goes in the background and then when you open the app it’s shows the wrong current location for the user until about 5 seconds. Is there to fix that because that 5 seconds delay ruins the tracking results ( it’s adds three extra miles for no reason ).

Edit: The issue wasn’t actually a “bug”. I have to set in my Info.plist that I want background pocessing and boom the application tracking is super Accurate. A little tutorial to do that:

1. Go to Info.plist
2. Add an New Row called “Required background modes”
3. Then add again a new row called “App registers for location updates”
4. We are Done 🙂

Answer 1

One thing you can do is check the horizontalAccuracy property on the CLLocation that you’re being returned. If this is above a certain threshold then you could throw away the result and wait for a more accurate one. If it is a number of miles out then I would expect the accuracy figure to be quite large. It’s most likely using a cell site to determine location rather than GPS, and the margin of error would be much greater.

In your CLLocationManagerDelegate‘s locationManager:didUpdateLocations: method you could do the following:

- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations {
  if ([locations count] > 0) {
    CLLocation *lastUpdatedLocation = [locations lastObject];
    CLLocationAccuracy desiredAccuracy = 1000; // 1km accuracy
    if (lastUpdatedLocation.horizontalAccuracy > desiredAccuracy) {
      // This location is inaccurate. Throw it away and wait for the next call to the delegate.
      return;
    } 
    // This is where you do something with your location that's accurate enough.
  }
}