Well nowadays you individually track by using mac addresses and other network information from the devices within range. Cisco has some creepy real time maps of your location with each person walking around and all their previous visits etc
You could for example flag a location (house) and get a list of all of the comings and goings over the last x months, then look them up by identity. You could also flag when an individual was in proximity to another, or when someone turned on, off or switched phones.
I’m sure it amounted to illegal surveillance and would be inadmissible if any of it was done without a warrant, but it would be beautiful for parallel construction. (How is that even constitutional???)
It apparently relied on some kind of infrastructure deployment that consisted of “traffic cameras” and “satellites” ( I’m certain not of the spacecraft type) that I assume were just small receivers mounted on street lights, since the streetlights were almost completely replaced at the same time as the cameras were put in, by the same out of state contractor.
I was there to change out a bad SSD and do a RAM upgrade on one of the servers. I don’t imagine the technology has become less invasive.
If you have a phone or carry active Bluetooth devices, assume you are 100 percent tracked 100 percent of the time.
If you care, slip it into a faraday bag instead of turning it off or going into airplane mode and you won’t be flagged nearly as likely. People rarely use airplane mode or turn off their phones in situations where it doesn’t provide a useful clue about activity.
There is a huge overlap between surveillance platforms and behavior analysis / data brokers.