The document discusses the history of GPS on mobile devices from iOS 3 to iOS 9. It covers how early versions of iOS had limitations that impacted battery life and background GPS tracking. It also discusses how later versions of iOS and features like background refreshing helped address these issues. The document then talks about techniques for filtering and smoothing GPS data as well as presenting location information to users.

1. History of Mobile GPS
Phillip Connaughton
The Evolution of
Mobile GPS
{MBLT} Dev ‘15
Phillip Connaughton
Principle Engineer @Runkeeper
@pconno3

2. History of Mobile GPS
Phillip Connaughton
Overview
• History of GPS on iOS
• Runkeeper filtering algorithms
• GPS bugs and gotcha’s
• Conserving battery life

3. History of Mobile GPS
Phillip Connaughton
Runkeeper and GPS
1. Collect finite points during the activity
2. Broader location data post activity
Used for realtime feedback (distance,
pace, calories, etc.)
Used for show the general area a
user ran in, location based
messaging and music

4. History of Mobile GPS
Phillip Connaughton
iOS 3
• Couldn’t operate in the background
• Keeping in foreground demolished
battery life
• Introduction of ‘Silent Audio Trick’
http://service.o2.co.uk/IQ/srvs/cgi-bin/webcgi.exe?
New,KB=Companion,question=ref(user):str(Mobile),CASE=19044

5. History of Mobile GPS
Phillip Connaughton
iOS 4 & 5
authorizationStatus()
significantLocationChangeMonitoringAvailable()
headingAvailable
startMonitoringForRegion(_:)
Introduced Region and Heading API’s

6. History of Mobile GPS
Phillip Connaughton
• Deferred updates
• Conserve battery life with
Hi-fidelity points
iOS 6
https://developer.apple.com/library/ios/documentation/CoreLocation/Reference/CoreLocationConstantsRef/index.html#//apple_ref/c/data/kCLLocationAccuracyBest
https://www.siliconbeachtraining.co.uk/blog/ios-7-new-features
- (void)locationManager:(CLLocationManager *)manager
didUpdateLocations:(NSArray<CLLocation *> *)locations;
- (void)locationManager:(CLLocationManager *)manager
didUpdateToLocation:(CLLocation *)newLocation
fromLocation:(CLLocation *)oldLocation;
• To enable
• Set accuracy to kCLLocationAccuracyBest
or kCLLocationAccuracyBestForNavigation
• Distance Filter kCLDistanceFilterNone

7. History of Mobile GPS
Phillip Connaughton
iOS 7
• Background Refresh (no longer impact on location
services in iOS 8 and up)

8. History of Mobile GPS
Phillip Connaughton
Background Refresh

9. History of Mobile GPS
Phillip Connaughton
iOS 8
Introduction of Location services Authorization
CLAuthorizationStatusAuthorizedAlways
CLAuthorizationStatusAuthorizedWhenInUse
Necessary for region monitoring and for launching
apps from the background
Great for in the moment location features or tracking

10. History of Mobile GPS
Phillip Connaughton
iOS 9 & watchOS2
[self.locationManager setAllowsBackgroundLocationUpdates:NO];
Nothing too exciting,
changed some permissions
watchOS 2 adds CoreLocation

11. History of Mobile GPS
Phillip Connaughton
Setting up
Location Services
• Setting up location services is really easy
func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation])
{
}
• Location Services is very noisy
self.locationManager.delegate = self //Register your class to receive updates
self.locationManager.desiredAccuracy = kCLLocationAccuracyHundredMeters // How close do we need to be?
self.locationManager.distanceFilter = kCLDistanceFilterNone //We will be informed of any movement
self.locationManager.requestWhenInUseAuthorization() // add NSLocationWhenInUseUsageDescription to
plist to explain location usage
self.locationManager.startUpdatingLocation()

12. History of Mobile GPS
Phillip Connaughton
Filtering Algorithm
• You will not receive points that are as accurate as
you asked. While Location Services start up you will
receive inaccurate points
• Need a large dataset for making real improvements
to filters
• Important to see every point given by the OS so
that you are improving filtering with complete
dataset

13. History of Mobile GPS
Phillip Connaughton
GPS Point
• Horizontal accuracy within radius of
certainty
• Points we throw out
• No cell tower points!
• Age - are they older than the
last point we got?

14. History of Mobile GPS
Phillip Connaughton
• Horizontal accuracy within radius of
certainty
• Points we throw out
• Acceleration, did the person
just jump across the city in a
few seconds?
• Horizontal accuracy < 0
GPS Point
• No cell tower points!
• Age - are they older than the
last point we got?

15. History of Mobile GPS
Phillip Connaughton
GPS Accuracy Level
Fine grained GPS Data • City Level Accuracy

16. History of Mobile GPS
Phillip Connaughton
Reverse Geocoding
let geocoder = CLGeocoder()
geocoder.reverseGeocodeLocation(locations[0]) { (placemarks, error) -> Void in
if (placemarks?.count > 0){
let placemark: CLPlacemark! = placemarks![0]
if(placemark.locality != nil && placemark.administrativeArea != nil){
NSLog(String(format: "Locality: %@, Area: %@", placemark.locality!, placemark.administrativeArea!))
}
}
}
Geocoder geocoder = new Geocoder(context, Locale.getDefault());
try {
List<Address> addresses = geocoder.getFromLocation(latitude, longitude, 1);
if(addresses.size() > 0)
{
Address address = addresses.get(0);
if (address.getAdminArea() != null && address.getLocality() != null)
{
Log.d("Location Example", "Locality:" + address.getLocality() + " Area:" + address.getAdminArea());
}
}
}
catch (IOException e)
{
e.printStackTrace();
}
iOS
Android

17. History of Mobile GPS
Phillip Connaughton
AutoPause
Don’t want runners to have to mess
with phone in armband while
running

18. History of Mobile GPS
Phillip Connaughton
Smoothing with Kalman
Filter
Normal GPS points Filters GPS points

19. History of Mobile GPS
Phillip Connaughton
Android Shuffle

20. History of Mobile GPS
Phillip Connaughton
Android Shuffle

21. History of Mobile GPS
Phillip Connaughton
Android Shuffle

22. History of Mobile GPS
Phillip Connaughton
Android Shuffle
Something wrong with sort?
Collections.sort(points, new Comparator<TripPoint>()
{
@Override
public int compare(TripPoint lhs, TripPoint rhs)
{
return Double.compare(lhs.getTimeAtPoint(), rhs.getTimeAtPoint());
}
});
We were setting the timestamps as
point.setTimeAtPoint(System.currentTimeMillis());
Returns the current time in milliseconds since January 1, 1970 00:00:00.0 UTC.
This method shouldn't be used for measuring timeouts or other elapsed time measurements, as changing the
system time can affect the results. Use nanoTime() for that.
http://developer.android.com/reference/java/lang/System.html#currentTimeMillis()

23. History of Mobile GPS
Phillip Connaughton
Elevation
We haven’t had much luck with
the OS but give it a shot!
http://topocoding.com
https://www.pinterest.com/pin/320459329711121377/
http://www.cliparthut.com

24. History of Mobile GPS
Phillip Connaughton
User Presentation
Thin Line Thicker Line

25. History of Mobile GPS
Phillip Connaughton
Battery Life
Don’t be here! GPS is a killer
Limit network calls

26. History of Mobile GPS
Phillip Connaughton
Conclusion
• iOS and Android continue to make location data
easier and easier to use
• Consider the users perception when displaying
location data to them
• Always be thinking about battery life