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An LAPD helicopter claimed to have ID'ed protesters from above and threatened to "come to your house"
(www.motherjones.com)
This is a most excellent place for technology news and articles.
It will always be a matter of "for how long?". Location from integrated acceleration is what we call a stiff problem. Meaning that any error is compounded as you continue to integrate (slight over simplification, but good enough for the point). There will never be a sensor that has zero error, so it's just a question of how much integration you can do before the errors make the results unusable.