Location information can be very sensitive. If you drive your car around the United States, it can reveal if you go to a therapist, attend an Alcoholics Anonymous meeting, if you go to church or if you don’t go to church. And when that information about you is combined with the same information about everyone else, the government can gain a detailed portrait of how private citizens interact.

One of the key technologies driving mass location tracking is the innocuous-sounding Automatic License Plate Reader. If you haven’t seen one, it’s probably because you didn’t know what to look for – they’re everywhere. Mounted on roads or on police cars, Automatic License Plate Readers capture images of every passing car and convert the license plate into machine-readable text so that they can be checked against hot lists of cars potentially wanted for wrongdoing.

When Mike Katz-Lacabe asked his local police department for information about the plate reader data they had on him, this is what they got: in addition to the date, time and location, the police department had photographs that captured where he was going and often who he was with. The second photo from the top is a picture of Mike and his two daughters getting out of their car in their own driveway. The government has hundreds of photos like this about Mike going about his daily life. And if you drive a car in the United States, I would bet money that they have photographs like this of you going about your daily life.

https://www.ted.com/talks/catherine_crump_the_small_and_surprisingly_dangerous_detail_the_police_track_about_you