First, he showed how a person might stalk celebrities. After hours
spent trawling through a search of images for ‘celebrities in taxis in
Manhattan in 2013’, Tockar found several pictures with a licence
plate in view. Cross-referencing these with celebrity blogs and
magazines, he worked out what the start point or destination was,
and matched this against the supposedly anonymous taxi dataset.
He could also see how much celebrities had – or hadn’t – tipped.
‘Now while this information is relatively benign, particularly a year
down the line,’ Tockar wrote, ‘I have revealed information that was
not previously in the public domain.’
Tockar acknowledged that most people might not be too worried
about such analysis, so he decided to dig a little further. He turned
his attention to a strip club in the Hell’s Kitchen neighbourhood,
searching for taxi pick-ups in the early hours. He soon identified a
frequent customer and tracked the person’s journey back to their
home address. It didn’t take long to find them online and – after a
quick search on social media – Tockar knew what the man looked
like, how much his house was worth, and what his relationship status
was. Tockar chose not to publish any of this information, but it
wouldn’t have taken much effort for someone else to come to the
same conclusions. ‘The potential consequences of this analysis
cannot be overstated,’ Tockar noted.
With high-resolution GPS data, it can be extremely easy to
identify people.[46] Our GPS tracks can easily reveal where we live,
what route we take to work, what appointments we have, and who
we meet. As with the New York Taxi data, it doesn’t take much to
spot how such information could be a potential treasure trove for
stalkers, burglars, or blackmailers. In a 2014 survey, 85 per cent of
US domestic violence shelters said they were protecting people from
abusers who’d stalked them via GPS.[47] Consumer GPS data can
even put military operations at risk. During 2017, army staff wearing
commercial fitness trackers inadvertently leaked the exact layout of
bases when they uploaded their running and cycling routes.[48]
Despite these risks, the availability of movement data is also
bringing valuable scientific insights, whether it’s allowing researchers