LESSONS LEARNED IN LOOKOUT

LOCATION SERVICES Jeff Watts, Lookout, Inc.

Locations @ Lookout

•  Collect locations in several scenarios: •  User-initiated •  Signal Flare •  Lock Cam •  More to come…

Lots of ‘em

•  Millions of location requests per day, and

growing

•  Most locate commands result in multiple

locations being obtained and sent from the

device

•  Devices have multiple location

providers (cell, wifi, GPS, etc.), with

varying accuracies and time to get a fix

So what have we learned?

1. Speed counts

•  Faster fixes = happier users

•  Get the first fix you can reasonably use,

refine later

•  Passive location provider is useful for this

•  Network location provider is faster than

GPS, but with lower accuracy

2. Know your accuracy threshold

•  Get there and stop listening

3. Raw cell tower info is rarely useful

•  Caveat: the previous point

•  Very low accuracy (~1 mile)

•  You’ll need another service to translate

CellID info to latitude and longitude

•  But fast! (see point 1)

•  Easy on the battery, too

4. Mind the battery

•  Don’t use GPS if you don’t have to

•  Passive location provider is nice, if you can

get what you need from it

•  Network providers (cell, wifi) are easier on

the battery than GPS

•  Can get pretty good accuracy with assisted

GPS, using network provider (requires GPS

chip on device, though)

5. Better APIs will make your life easier

•  If device has Google Play services, you may

be able to use fused location provider on

Android, which hides most of this

complexity from you

•  Similar API for iOS, available on all devices

6. Be nice to your DB

•  Keep writes fast, index judiciously

according to your app needs

•  Multiple locations sent from a device for

each location request

•  Probably don’t need to keep all of them

•  Figure out how to group related

locations