This technology allows the police to cruise through a city at normal speed and photographically gather images of vehicle license plates, along with geolocation data. This is all stored, and can easily be used to create a record of everywhere your car has been. Coupled with cellphone and WiFi data being collected along with its own geodata, and tied to things like tracked credit card activity, emails and the now-ubiquitous public surveillance cameras, it is very, very easy for law enforcement to know where you are, where you have been and have a pretty good idea of what you were doing.