A powerful component of mobile development is being able to have our iOS and Android apps work with and respond to a device’s location. Whether developing natively or using cross-platform tools, there are several methods for obtaining location. Since we are dealing with our user’s privacy, and their device’s battery life, we want to do it right!

1. GEOLOCATION WITH MOBILE APPSAdam Paxton
Connect.tech Atlanta
September 21st, 2017

2. PRESENTATION NOTES
bit.ly/mobilegeotalk

3. OVERVIEW
➤ A little GPS background
➤ Our responsibilities as devs and product owners
➤ What’s available on iOS
➤ And Android
➤ Location considerations cross platform

4. HELLO
➤ Adam Paxton
➤ Freelance Mobile App Developer
polancomedia.com
➤ Location API
condesa.io
Twitter: @adampax
Github: adampax

5. GLOBAL POSITIONING SYSTEM
➤ Satellites!
➤ Run by US Govt
➤ ~ 3 meters accuracy
➤ Trouble with obstructions
➤ inside buildings
➤ In canyons, skyscrapers
➤ Water
➤ Phones contain actual GPS hardware
➤ Power intensive!
➤ Takes time to determine location
(not a gps satellite)

6. ASSISTED GPS

7. ASSISTED GPS
➤ Helps with 3 big problems of GPS…
➤ Power consumption
➤ Response time
➤ Accuracy in buildings, etc
➤ …by using other stuff available on the phone
➤ Wifi signals
➤ Cell towers

8. DEVELOPER RESPONSIBILITIES
➤ Privacy
➤ Accurate reasons for authorization
➤ Battery conservation
➤ Privacy!

9. AUTHORIZATION
➤ Both platforms require the user to
explicitly grant permissions for your app to
use location.
➤ Android
➤ ‘Coarse’ or ‘Fine’ permission in manifest
➤ Runtime permission
➤ iOS
➤ Runtime permission of either
➤ ‘While in Use’
➤ Always
➤ Description of why permission is needed

10. AUTHORIZATION CONT’D
➤ Must handle case when permission is
denied or later removed
➤ ‘Pre-permission’ a popular option
➤ Give users a heads-up message prior to
asking for permission
➤ Recommended to wait to ask until
service is needed

11. IOS GEOLOCATION
➤ Core Location Framework contains
➤ Standard location service
➤ Significant-change location service
➤ Region monitoring
➤ Visits
developer.apple.com/documentation/corelocation

12. STANDARD LOCATION SERVICE
➤ Examples:
➤ Turn by turn navigation
➤ Get weather for current location
➤ Pros: Highest accuracy, Most configuration options
➤ Cons: Drains the battery
➤ Two Approaches:
➤ Onetime location request: requestLocation()
➤ Continually track location: startUpdatingLocation()

13. STANDARD LOCATION SERVICE CONT’D
➤ Return Data:
➤ Coordinates - Latitude/Longitude
➤ Accuracy in meters
➤ Altitude accuracy in meters
➤ Config options:
➤ Distance filter - min distance you move before generating another event
➤ Desired accuracy
➤ Activity type - power saving option to help device know when you’ve stopped
➤ Pause location automatically - power saving option

14. SIGNIFICANT-CHANGE LOCATION SERVICE
➤ Very low precision location tracking service
➤ Pros:
➤ Highly efficient battery usage
➤ Persists through device restart
➤ Cons: Very coarse location tracking, think 500m - 1k
➤ Apple now considers this a niche-usage service
➤ ‘Always’ authorization

15. REGION MONITORING, AKA GEOFENCING
➤ Example: App notifies user of sales when arriving at store location
➤ Pros:
➤ Highly efficient battery usage
➤ Persists through device restart
➤ Only receives location updates when entering/existing relevant regions
➤ Cons:
➤ Max 20 regions supported at one time
➤ Not always firing location event?
➤ Define region with set of coordinates and a radius
➤ ‘Always’ authorization

16. AND BEACONS!
➤ Similar to Region Monitoring, with Bluetooth beacons
➤ Place beacons anywhere, identify by unique ids
➤ Can determine a rough distance or range between device and beacon

17. VISITS LOCATION SERVICE
➤ Examples:
➤ Journaling app listing places visited throughout the day
➤ Music app that prepares gym playlist when user arrives at gym
➤ Pros: Highest level of battery efficiency
➤ Cons:
➤ After the fact info, not for realtime or near realtime location decisions
➤ Up to iOS to determine what constitutes a ‘visit’
➤ Return Data:
➤ Coordinates
➤ Horizontal accuracy in meters
➤ Approximate arrival & departure time, if applicable
➤ ‘Always’ authorization

18. ANDROID GEOLOCATION
➤ Fused Location Provider
➤ As in ‘fuses’ together location data
from GPS, Wifi, etc.
➤ Fewer ‘services’ than iOS, but more
configuration options
➤ requestLocationUpdates()
➤ getLastLocation()
➤ Geofence Provider
➤ Running in an Android Service
developer.android.com/training/location/

19. ➤ Start receiving device location updates, similar to iOS startUpdatingService()
➤ Configuration Options
➤ Interval - preferred rate of receiving updates
➤ May be affected by other apps requesting faster updates
➤ Or by no updates being available
➤ Fastest Interval - set an upper limit on what your app can handle
➤ Priority - Set preference between accuracy and power consumption
➤ Number of updates - Stop receiving locations after x updates
REQUEST LOCATION UPDATES

20. ➤ Number of updates - Stop receiving locations after x updates
➤ Expiration duration - Like the number of updates, but stop after a period of time
➤ Max wait time
➤ Smallest Displacement - Minimum ‘distance’ between location updates
REQUEST LOCATION UPDATES CONT’D

21. ➤ Get the devices last known location
➤ Usually the same as the current location
➤ No waiting, not async
➤ Might be empty!
GET LAST LOCATION

22. GEOFENCES
➤ Similar setup as iOS
➤ Limited to 100 per device
➤ Minimum radius accuracy
➤ 100-150 meters
➤ Or 20-50m with Wifi
➤ Dwell option to set a minimum loitering
time before an entrance alert is sent

23. ANDROID SERVICES AND BACKGROUND LOCATION
➤ Run an android service to periodically request location
➤ Can set regular intervals, or get ‘hot’ or ‘cold’ around specific areas
➤ Combine with boot event receiver to restart after device reboot
➤ Background location service
➤ Re-register geofences

24. CROSS PLATFORM CONSIDERATIONS
➤ Expect different behavior and abilities between platform
➤ Depending on your goals, implementation may be easier on either platform
➤ Teach product owners importance of privacy!
➤ Complement Android location with background services
➤ Consider combining multiple options on iOS, depending on goal

25. THANKS
bit.ly/mobilegeotalk