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About this NOTAM airspace data

How this data is produced

1. Source. NOTAMs are obtained from the NATS UK area briefing service (nats-uk.ead-it.com) for the two UK Flight Information Regions — EGTT (London FIR) and EGPX (Scottish FIR), together covering the whole of the United Kingdom. The briefing window is the selected date, 00:00 to 23:59 UTC. The selection logic replicates the open-source NavPlot program (ahsparrow/navplot2) that produces the daily briefings published at navplot.asselect.uk; if the direct NATS feed is unavailable, those published briefings are used as a fallback.
2. Date filter. Only NOTAMs in force on the selected date are kept — those whose start date is on or before the date and which are either permanent or have an end date on or after the date.
3. Subject filter (by ICAO Q-code). A NOTAM is included only if it is one of:
   • Restrictions of all types except Overflight. Restrictions applicable to unmanned aircraft systems (UAS) only are excluded.
   • Warnings of type: Air Display; Aerobatics; Glider Flying; Missile, Gun or Rocket Firing; Parachute Dropping Area; and Radioactive Materials and Toxic Chemicals.
   • Activation or installation of airspace of type: Control Zone (CTZ), Control Area (CTA), ATS route, Terminal Control Area (TMA) and Aerodrome Traffic Zone (ATZ).
4. Size filter. Only NOTAMs with a notified radius of 30 NM or less are included, with one exception: temporary restricted areas — RA(T) — are always included regardless of radius. Larger NOTAMs (other than RA(T)) are excluded.
5. Geometry conversion. Each included NOTAM is converted to an airspace volume from the geometry described in its text: circles, coordinate polygons and arcs of a circle. Activations of named Danger Areas are resolved to their published coordinates using the national airspace dataset (see Sources). Where a NOTAM's geometry cannot be parsed from its text, an approximate circle may be derived from the ICAO Q-code centre point and radius, and/or from the autorouter NOTAM service. Any NOTAM whose geometry still cannot be determined is omitted and recorded as skipped — it is never silently guessed.

Sources

• NOTAM data — NATS UK area briefing (nats-uk.ead-it.com), FIRs EGTT + EGPX.
• Selection algorithm — NavPlot (ahsparrow/navplot2), the program behind navplot.asselect.uk.
• National / named-airspace geometry — openAIP (Great Britain dataset) and the YAIXM UK airspace data (ahsparrow/airspace).
• Supplementary coordinates — the ICAO Q-code centre/radius and the autorouter NOTAM API.

Abbreviations

• AMSL — Above Mean Sea Level
• ATS — Air Traffic Services
• ATZ — Aerodrome Traffic Zone
• CTA — Control Area
• CTZ — Control Zone
• FIR — Flight Information Region
• FL — Flight Level
• ICAO — International Civil Aviation Organization
• NATS — National Air Traffic Services
• NM — Nautical Mile(s)
• NOTAM — Notice to Airmen
• RA(T) — Restricted Area (Temporary)
• TMA — Terminal Control Area
• UAS — Unmanned Aircraft System
• UTC — Coordinated Universal Time