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Since the rise of the smartphone location tracking has become ubiquitous and is an increasingly controversial and misunderstood technology. This talk will discuss the latest approaches in location tracking across the major mobile platforms (iOS, Android and Windows Phone) and indoor location solutions such as Apple's iBeacon. It will offer practical tips on balancing accuracy with battery life, handling user privacy preferences and avoiding being creepy. About Richard: Richard is a software developer with eleven years experience at Multimap, BBC, Streetlife, Microsoft, and now Axon Active AG. Richard's expertise is in building large-scale web platforms, geo services and, most recently, mobile apps. He is based in Edinburgh, where he is most often to be found in cafés escaping the Scottish weather, and is passionate about well-designed products and services of all forms.
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R I C H A R D K E E N
(Enemy of the) State of Mobile Location Tracking
20,000 points over 232 days 15,000 miles travelled at an average of 2.6 mph
M E T H O D S O F L O C AT I O N T R A C K I N G
• On-device sensors (GPS etc.)
• Network provider tracking
• Indoor Wi-Fi scanning
• “Smart” rubbish bins…
W H Y T R A C K D E V I C E L O C AT I O N
• Safety & security
• Logistics
• Friend finders
• Fitness
• Journaling/quantified self
• Anticipatory computing
H O W I S A L O C AT I O N D E T E R M I N E D
Sensor Accuracy SpeedPower
consumptionCaveats
GPS ~40mSlow
(3 seconds+)High
Rarely works indoors
WiFi triangulation ~70m Fast MediumRarely works in
rural areas
Cell triangulation Cell ID 200m-1km Fast Low
R E Q U E S T I N G A S I N G L E L O C AT I O N
• Even single location updates come as an asynchronous stream – not a single final value
• Initial location is often cached and stale
• The user may be moving around as you request their location!
A N AT O M Y O F A L O C AT I O N
• latitude
• longitude
• altitude
• accuracy (horizontal and vertical)
• speed
• bearing
• timestamp
T R A C K I N G C H A L L E N G E S
• Power consumption
• Multitasking/background processing support
• Privacy settings (global & per-app)
• Device reboots
• Airplane mode, Wi-Fi disabled, cellular disabled
• Testing
S TA N D A R D L O C AT I O N S E R V I C E S
• Delivers a constant stream of locations over time
• Supports background multitasking (limited on Windows Phone)
• Power hungry with default settings
• Tracking won’t survive device reboots*
• Consider power impact of your callback code as well
S TA N D A R D L O C AT I O N S E R V I C E S - I M P R O V I N G P O W E R C O N S U M P T I O N
• On iOS & Windows Phone, manage power usage through location manager settings:
• desired accuracy level
• distance or time threshold between notifications – helps to reduce processing overhead
• iPhone 5+ & Google Nexus 5 support deferred updates & sensor batching
S TA N D A R D L O C AT I O N S E R V I C E S - I M P R O V I N G P O W E R C O N S U M P T I O N
iOS desiredAccuracy Power usage Highest power sensor
kCLLocationAccuracyBestForNavigation High GPS+
kCLLocationAccuracyBest High GPS
kCLLocationAccuracyNearestTenMeters High GPS
kCLLocationAccuracyHundredMetersMedium (urban)
High (rural)WiFi (urban) GPS (rural)
kCLLocationAccuracyKilometer Low Cell
kCLLocationAccuracyThreeKilometers Low Cell
Android priorities Accuracy Power usageHighest power sensor
used
PRIORITY_HIGH_ACCURACY Building-level High GPS
PRIORITY_BALANCED_POWER _ACCURACY Block-level Medium WiFi
PRIORITY_LOW_POWER City-level Low Cell
PRIORITY_NO_POWER Varies None Varies
S TA N D A R D L O C AT I O N S E R V I C E S - I M P R O V I N G P O W E R C O N S U M P T I O N
S I G N I F I C A N T C H A N G E N O T I F I C AT I O N S
• Only available on iOS
• Low power overhead, relies on cell tower transitions
• On average notification triggered after a movement of around 500m and more than 5 minutes
• Survives reboots of the device
• Very useful in hybrid strategies
G E O F E N C E S
!
• Geofence is a region defined by a co-ordinate and radius (in this context)
• Can request background notification of entry or exit of the region (& dwelling on Android)
A
B
E X I T A
E N T E R B
G E O F E N C E L I M I TAT I O N S
• Often quite a lag, doesn’t always trigger
• Not available on Windows Phone
• iOS supports up to 20 per app, Android up to 100
• Survives reboots on iOS, not on Android
H Y B R I D S T R AT E G I E S
Your app will have unique tracking needs; the default strategies are rarely the most appropriate
!
Find the ideal balance of quality, power use, granularity and frequency for your app
A N A S I D E : A P P L E M 7 & S I M I L A R
• iPhone 5S shipped with Apple M7 “motion co-processor”
• Does not relate to location data
• Google Nexus 5 and Moto X ship with “hardware sensor batching” – equivalent functionality
• Currently provides step counting & activity detection
T O O L S
• Profiling tools allow you to monitor use of GPS over time
• For iOS use Instruments, untethered capture supported via iPhone settings
• For Android use Qualcomm Trepn plugin for Eclipse
B L U E T O O T H B E A C O N S
• “iBeacon” – Apple specification for Bluetooth 4 location beacons
• Indoor high-accuracy location triggers
• Indoor positioning
• Opt-in via install of app tied to iBeacon namespace
T H A N K S !
@richardkeen
iOS reference: http://bit.ly/19O9PZS
Android reference: http://bit.ly/18mMnSX
Windows Phone reference: http://bit.ly/1aJu6y8
