In 2009, the German newspaper Die Zeit published an animated map of six months in the life of Malte Spitz, a Green Party politician, using his mobile call details records (CDRs). These are the logs of how, when, where and with whom he communicated, collected by his phone supplier for billing purposes.
By matching these records to mentions of Spitz’s political life on websites and blogs, Die Zeit was able to pinpoint the places the politician visited, the routes he took, how long he’d stayed in each location, and the people he’d texted and spoken to on the phone at the time.
Die Zeit and Spitz wanted to reveal how potentially intrusive the retention of CDRs can be in the way that they can track individuals from one cellular antenna tower to the next. Now, nearly a decade later, CDRs are being used to map the movements of millions of people at once.
These new population-scale movement-mapping techniques are based around anonymised aggregations of CDRs...