Batphone: Acoustic indoor localization
For my thesis work I am developing a set of techniques for determining the location of smartphones while indoors (where GPS is unavailable). I have released an Apple iOS (iPhone, iPod, and iPad) app which demonstrates the technique. It is available for free on the iTunes store.
This work is part of the Empathic Systems project at Northwestern University and is co-authored with Peter A. Dinda (Northwestern), Robert P. Dick (Univ. of Michigan), and Gokhan Memik (Northwestern).
The App
Batphone is a research tool which tests a new method of indoor localization. It uses the microphone to record room ambience. These acoustic room fingerprints are used to recognize previously-tagged rooms when they are revisited. For comparison, it also shows the position retrieved from Location Services, which determines your coordinates using radio signals from GPS satellites, wifi and cellular base stations. Our experiments have shown that Batphone’s new acoustic method is more accurate than the radio method. Try it for yourself and let us know what you think!
Batphone does not send any data to us. The only privacy risk for you is that location queries are sent to Apple; this is true of many apps and it can be disabled.
Known issues
These issues may be fixed in a future software release.
App will crash on iPod touch (2nd or 3rd generation) if a microphone is not plugged-in.
Changelog
Version 1.2, released on July 29, 2011, brought these changes
Tweaked UI
Fixed accuracy bug on iPhone when Wi-Fi was not enabled
These issues were fixed in the version 1.1 release on January 27, 2011
On iPhone 4, app sometimes hangs on the initial "waiting for ten seconds of data..." screen.
Data and Code
The source code for version 1.2 of the app is available here.
Experimental data (recordings) and Matlab code are available here.