[SlowRobotAhead]

Huh?

The contact tracing is 100% Bluetooth.

You post a beacon periodically, other people post beacons, everyone is listening for that UUID and records and instances of it. This is how the whole thing works.

GPS would be a privacy disaster, if it it did work for this. Random rotates beacons are a privacy issue if you don’t trust your phone mfg, which you should not, but as long as it’s an optional thing is O.K. in the way AppleGoogle are proposing.