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Comment by xg15 | Hacker News Reader

Lane specific driving directions?

How many Wifi access points and Bluetooth beacons is Google expecting to find on the highway while moving at 70mph?

This may be Waze beacons which use bluetooth to help position the user when they're going through tunnels, where there is no GPS coverage.

https://support.google.com/waze/partners/answer/9416071?hl=e...

https://www.theverge.com/2019/1/29/18202359/waze-beacons-nyc...

...positioned to give you a 1-dimensional measurement: how far are you along this specific tunnel? Expecting triangulation is, well, overly optimistic. By an order of magnitude, at least (and would require a far denser mesh of beacons, whereas this only needs one beacon every $measure ; or two, for added redundancy).

In other words, it's still useful for navigation like "you are now 2000 meters/yards/cubits into the tunnel, therefore you should be taking either of the two middle lanes", but the trick is, this doesn't require the app to know your current lane.

How about in town, going 20mph?

Most of the android tracing that I've seen logged on location history is wifi multilateration based. Since wifi is on most of the time, it's the quickest way of finding your location (since you're most likely on the road), and you can turn off GPS saving about 25mW or more of power.

But it does mean you need WiFi on negating any power saving you make from disabling GPS anyway.

I would presume they're hoping to find the devices of other nearby users?

But those would be in random cars around you, which are constantly moving. How could those help retrieving your own location on a map?

If there is a car travelling the same direction as you but a bit to the right, then you are not in the rightmost lane.

How would the phone know the wifi signal is coming from your right?

Because we also know about the car going in the other direction, and you came closer to it. Hypothetically.

Or if gps errors are correlated between phones.

Good point. Ok what about this then: Check the relative strength of cars travelling opposite way compared to same way.

I suppose if there are enough cars, and if you have access to the wifi and location data for enough of the phones, it might be possible to determine someone's relative location by triangulating the signal strength from multiple vantage points.

So my phone by itself doesn't know the direction of the signal, but two or more other phones could combine our location data with relative wifi signal strength and potentially get a better idea of where the signal is coming from. (I had forgotten that we were talking about an entity that potentially knows the data from all the devices, not just one endpoint.)

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