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Do the phones have to be open and navigating somewhere,or is it enough for them to just be idle on the home screen?
If it was only phones running Maps, they wouldn't get much data.
Phones running Maps are actively using the GPS, so they provide more precise data. Those sitting idle just get tower location, which helps fill in some vague flow information but doesn't do much for specific street or momentary speed.
Why can't the phones determine their proximity to each other and report it to Maps, which would then presumably figure out that they're too close to represent separate vehicles?
Because GPS in built-up areas has super low precision and position estimates jump by tens of meters. A cart of phones is going to be almost indistinguishable from a pack of cars.
"But missosoup don't phones also have accelerometers and gyros?"
Sure, but they're used to feed into a Kalman filter that produces the position estimate. Apps don't generally access high resolution sensor feeds because the positioning service is already doing the best job possible. Even with that, it's hard to distinguish multiple cars accelerating from a green light compared to a bag of mobile phones being carted around.
tl;dr: it's hard. Measures can be taken to filter out these attacks but they'll come at the expense of reducing the accuracy of regular traffic data. Unless these attacks start becoming a real problem, it's probably not worth it.
I'm stunned how fast Google Maps detects traffic jams. I assume all those smartphones are running car navigation and as traffic detection works by trusting the clients I fear there's no chance to avoid this kind of exploit. Nevertheless it would be interesting to know what's the ratio of correct / malicious clients to fool the system. That migt highly depend on whether Google implemented any detection of faulty clien…
I think gps accuracy is something like 3 meters, which is about one car length.
For example, could shops use it to inflate their footfall and make them look busier than they are ?
Can you think of any other areas where this hack could be used for non-ethical purposes ?
Why can't the phones determine their proximity to each other and report it to Maps, which would then presumably figure out that they're too close to represent separate vehicles?
Just a guess: there's little economic incentive to perform this attack, and it would also be pretty expensive to perform regularly. So detecting and preventing it has not been a priority up to now. If people started doing it regularly, I'm sure countermeasures would be put in place.
BTW I wonder if you really need 99 different data Sims cards or rather have a smartphone hotspotting every 5.
I wonder if there are other non-ethical commercial purposes for this. For example, could shops use it to inflate their footfall and make them look busier than they are ? Can you think of any other areas where this hack could be used for non-ethical purposes ?
In a suburb, surely 20 phones would be enough, no? At $30/ month maybe somewhere between 500 and 600 per month?