Your iPhone isn’t following your every move

Some background:

Researchers Pete Warden and Alasdair Allan discovered that iPhones have been storing a file on your phone that records timestamped location data. This file is backed up to your computer when you sync, and it’s been happening since iOS4.

The common claim is that this data tracks your every move. For example, CNN says, Warden and Allan’s app can display “everywhere you’ve been since the tracking started.”

I’m only running an iPhone 3G, not an iPhone 4, so my experience may be atypical, but my iPhone hasn’t been tracking my every move. It looks like it has recorded the location only when I made use of the location services (Maps, Latitude, or FourSquare, for example). It does suggest a possible way to avoid this tracking if you’re really worried: don’t use location aware services.

Here’s how I came to this conclusion…

I downloaded the source code for Warden and Allan’s application ( They intentionally limit their application to only report only aggregated weekly data, and the location data is confined to a coarse grid. Two small tweaks to the source code allowed me to see location data down to the second accuracy, and at a much more accurate spatial resolution. (If you want the details of how to do this, just get in touch.)

I was excited! I wanted to see the paths that I followed around North America… San Francisco, Winnipeg, Montreal, Vancouver, Seattle, and lots more of Vancouver. I was disappointed. I rarely saw a little stream of location markers showing “my every move”. I looked closer at the data; it was sporadic. Days would go by without a timestamped location. Other times, like when I was using Latitude to update my location during a bus trip from Vancouver to Winnipeg, updates happened more often, sometimes multiple times per minute.

Here are shots of two successive time bins:

Where was I between those two events? You’ll never know! I’ll never know!

I can match almost every instance where my every move was logged to a situation where I was headed some place new, and I was using Google Maps.

So, maybe, this location database is not as extreme or as cool as it seemed at first.

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