Your cell phone company knows everywhere you go, twenty-four hours a day, every day. How concrete is this fact for you?

It's very concrete for Malte Spitz, a German politician and privacy advocate. He used German privacy law — which, like the law of many European countries, gives individuals a right to see what private companies know about them — to force his cell phone carrier to reveal what it knew about him. The result? 35,831 different facts about his cell phone use over the course of six months. As the German newspaper website Zeit Online reports:

This profile reveals when Spitz walked down the street, when he took a train, when he was in an airplane. It shows where he was in the cities he visited. It shows when he worked and when he slept, when he could be reached by phone and when was unavailable. It shows when he preferred to talk on his phone and when he preferred to send a text message. It shows which beer gardens he liked to visit in his free time. All in all, it reveals an entire life.

To show just how extensive this data is, Spitz chose to make it all available to the public; Zeit Online used it to prepare a remarkable interactive map, which animates Spitz's movements, moment by moment, over the course of half a year. It's correlated with information Spitz willingly posted on the web, and, according to him and the newspaper, is remarkably, eerily accurate. Try it out.

A report in the New York Times on Saturday described the data release, which it called "astounding", and put it in a U.S. context, quoting EFF's Kevin Bankston. The Times tried to find out whether U.S. mobile phone carriers have similar data about their subscribers, but it said "[t]he major American cellphone providers declined to explain what exactly they collect and what they use it for."

EFF has been following this issue for years and has worked extensively to limit government access to location data about individuals; government agents have increasingly sought to use this information, using questionable legal arguments to get carriers to turn it over. Still, it's remarkable to see an actual location data set about a real person. (According to the Times, German carriers have, for legal reasons, now stopped routinely storing this data. However, like all mobile phone carriers, they still have the technical ability to collect it at any time.)

Malte Spitz explains why he worked to obtain this information: to help educate the public about some of what's at stake in the German and worldwide debates about telecommunications data retention. All around the world, including the United States, proposed laws would force carriers to retain enormous quantities of personal information. As Spitz and Zeit Online have shown, these troves of information can give a detailed picture of each person's private life.