A direction
is not a
position.

Watch what the error readout does as you add nodes. One node: there is no error number, because there is no fix, only a direction. Two nodes: a fix appears but it skews wildly as you drag along certain angles. Four well-spread nodes: the fix locks to a few metres and barely flinches.

That is the entire argument in one motion. The phased-array tile contributes a bearing and nothing more. Everything that makes a bearing dangerous, the distance, the point, the dot on a map an officer can dispatch to, comes from separation between nodes and from correlation across them. A surveillance camera network already ships both. It is a grid of fixed, surveyed, time-synchronised points that already pool their observations into one dashboard. Adding receive-only DF tiles inherits that topology for free.

Notice the second readout: geometry quality. When all nodes sit on one side of the emitter, the bearings cross at a shallow angle and the fix smears into a long ellipse, even with low per-bearing noise. Spread the nodes around the target and the same noise collapses to a tight point. This is why coverage density, not sensor sensitivity, is the real escalation. A city does not need better antennas. It needs more poles, and it already has them.

The naive version of device tracking reads a MAC address off a probing phone. Modern handsets defeat that by rotating the MAC to a random value, so the obvious identifier melts between reads. Press Rotate MAC above: Key B's address changes, and a system that keyed on the address loses the trail.

But the address is the logical layer. The physical layer does not rotate. Every radio has manufacturing imperfections, oscillator drift, clock skew, power-amplifier nonlinearity, that bias its emissions in a way that is stable for the life of the hardware. Take enough reads and those imperfections form a fingerprint that survives the MAC change. Press Take another read and watch the fingerprint bars reconverge while the address keeps lying.

Now press Join the graphs. A stable device key, repeatedly co-located with a stable plate key at the same poles at the same times, joins the two. The car was never the point. The car was the introduction. After the join, the device follows the person: out of the car, into the building, onto the bus, to the meeting, home. The plate is forensic. The fingerprint is biographical.

The same asymmetry runs through the constitutional posture, not just the spectrum rules. A camera network's standing defence is the public-exposure logic: a plate faces the street, a car on a road has a reduced expectation of privacy, the system only logs what any bystander could see. That argument is built for plates.

It fits a passively-collected fingerprint of a device in your pocket far worse. The signal is not knowingly exposed the way a plate bolted to a bumper is. And aggregated location drawn from a personal device, accumulated across nodes into a pattern of life, is precisely the category that courts have already flagged as different in kind from a single observation. The fingerprint-plate join does not extend the old defence. It walks the system into the territory the old defence was built to stay out of.