Explainer
Unknown Is Not Zero: Reading Airspace Without False Reassurance
Why an empty display must never be read as an empty sky, and how a state can say what it does not know.
Evidence levelE0Concept
In brief
An empty display does not mean an empty sky. It may mean that nothing was there, or that nothing could be seen. A good airspace state separates the two and says which one it is.
The question
When a screen shows no aircraft, what is the viewer entitled to conclude?
Context
Every source sees only part of the airspace. A sensor has places it cannot reach, weather that weakens it and moments when it is offline. If a display shows only what was detected, the silence of a source looks exactly like the silence of the sky, and the reader fills the gap with reassurance.
How we approach it
The platform is designed to carry three answers rather than two: present and observed, absent where a source could have seen it, and unknown where no source could. Unknown is drawn as unknown, never as blank space. Confidence, evidence and source health are kept apart, so a confident track from a degraded source is shown for what it is.
What follows
A state that can say “I do not know” is more useful than one that is always sure. When degradation reduces what is known, the claim weakens first, and the picture must not look more certain than the data behind it. This is a design principle at E0; no result has been measured.
What this does not establish
- That any AIR NEXUS source can reliably detect an aircraft.
- That an airspace shown as empty by any system is safe.
Limitations
- This is an explainer of a design principle, not a report of a tested behaviour.
- It describes how a state is designed to be shown, and says nothing about how well any source detects anything.
- The three-answer model is a simplification; a real state carries more detail than present, absent and unknown.