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Triangulator (in Swift)

This app demonstrates how to triangulate distance between iBeacons using CoreLocation. I wrote it for a class I teach as part of Twitter's internal training program.

Triangulation is not precise because you only have 4 distances you get when ranging an iBeacon (immmediate, near, far and unknown).


Click on the bottom-left triangle icon (it should turn gray) to configure the iBeacons you have to match their real-life location, and click again on the triangle when you are done.

Next, click on the bottom-right scan icon to start scanning for iBeacons. Once iBeacons are in range, the location marker icon should appear. It's default position is offscreen (at -100, -100).


This works on an iPhone 4S running iOS 7.1, with Estimote iBeacons.


If the app doesn't working, you may need to restart your iOS device. I've noticed with any BLE/iBeacon stuff that seems to be the only thing that works. And then it's all fine until the next time!

CoreLocation vs CoreBluetooth

I am using CoreLocation, which is the only accepted way of interating with iBeacons. CoreBluetooth doesn't give you the background capabilities needed in a distance-aware app.

CoreLocation gives you iBeacon class (proximity UUID), major and minor (think of them as ways to give an iBeacon a unique ID). CoreBluetooth gives you only a deviceUUID. In fact, the information available to CoreLocation and CoreBluetooth is mutually exclusive- they handle the iBeacon advertisements differently.


  • The app is hardcoded to use 3 iBeacons. The triangulation code could handle more of them, but the iBeacon setup would need to be modified to support this.
  • The triangulation code doesn't handle the 0 < n < 3 signal case. When there are only one or two iBeacons present, we should do something different with the UI. The same goes for 0 iBeacons.
  • To make CoreLocation work in iOS 8, you need to add stuff to the plist! See:

Shamelessly Stolen Artwork


  • People who's artwork I stole (see above)
  • Coworkers at Twitter who made helpful suggestions to my coding style
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