[LXicon]

ground patrol cars or aerial surveillance require a person to operate them. GPS tracking allows for tracking many targets at once and then sifting through the data to find "bad guys".

the added costs of having a person track a target means more care is taken to avoid false positives. the person doing the tracking can also dis-regard irrelevant data that an automated system might erroneously use.

imagine some program that automatically sifted through a source of ubiquitous GPS data which actually did catch 100% of all terrorist attempts in New York in 2010 (the Times Square bombing attempt). what if that system meant 100 false positives were added to the no-fly-list because they drove on street X on date Y followed by street Z within 2 days (or some other such algorithm) when (if) someone asks about these no-fly-list additions they are simply told that the suspects exhibited behavior that was consistent with the Times Square bomber... if you are not a terrorist, you have nothing to hide!

[jackpirate]

GPS tracking allows for tracking many targets at once and then sifting through the data to find "bad guys".

Excellent point. Professional statisticians make these mistakes all the time. It is widely considered the reason that so much published scientific research is false. If professional statisticians make these errors, then how can we expect the average policeman not to?

[tptacek]

The number of people the FBI can surveil with these devices is, while larger than the number of people they can tail in cars, still tiny. That's why I'm OK with it.

The number of people they could surveil with a court order for access to OnStar data is so great that I don't even think they should be able to get court orders for bulk access to OnStar data.

[chc]

Eh, that's true, but at the same time, tiny is relative. For perspective: The low-end cost of commercial GPS tracking devices is about $50 (as determined by searching Amazon). Assuming the FBI can get a bulk deal on a tracker around that price point, it could track every single Muslim in America for less than its annual construction budget.