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Very cool. They are using Time Difference of Arrival analysis[1], the fact that most devices have two or more antennas, and clever software to get 10-80 cm accuracy at a good enough frequency to be used as a positional reference in a quadcopter, see the paper[2] for more info

Existing indoor positioning systems such as Bluetooth LE beacons and WiFi triangulation[3] only use the RSSI value and trigonometry to figure out the position. This method is slow (5Hz or so) and the resolution of the RSSI is bad unless you sample it directly, eg with SDR (which incidentally, is what my dissertation is about!)

[1] https://en.wikipedia.org/wiki/Multilateration#Principle

[2] https://www.usenix.org/system/files/conference/nsdi16/nsdi16...

[3] https://www.qualcomm.com/products/izat (unfortunately there are no public 'specs' I can find...)

Point of note: Multilateration (link [1] above) is the real name for the process that ordinary people casually call "triangulation" when they're talking about wifi location. It's not actually triangulation (which determines location based on the angle) but it's based on circles (or spheres, I guess - based on the distance).

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