Archive Methodology & Data Pipeline
Technical explanation of how TFR Archive captures, normalizes, classifies, and permanently preserves temporary flight restrictions across United States national airspace.
- 15-Minute Polling Cadence: Many TFRs exist for only several hours; a 15-minute polling interval captures short-lived stadium, VIP, and hazard restrictions.
- Deterministic Rule-Based Classification: Uses statutory citations (14 CFR) and audited regex patterns rather than generative LLMs for reproducible classification.
- Full Version Diffs: Every revision published by the FAA creates a new immutable version record with a geometric and text diff.
- Canonical Storage: Hosted on MySQL InnoDB utf8mb4 with normalized airspace cylinders and polygons.
1. Why 15-Minute Polling
Standard daily web scraping is insufficient for temporary flight restrictions. Many stadium TFRs exist for only five hours during a game. Hazard firefighting TFRs can be issued, expanded, and cancelled within a single afternoon. By polling official FAA endpoints every 15 minutes, the capture pipeline records short-lived restrictions and amendments before they disappear.
2. Versioning and Change Detection
Every poll computes a cryptographic SHA-256 hash of the incoming TFR detail document. If a hash changes, the pipeline creates a new immutable version record (v2, v3, etc.) and computes a diff highlighting radial expansions, altitude modifications, time extensions, or cancellation notices.
3. Deterministic Classification
To guarantee reproducible and audit-safe classifications, TFR Archive uses code-based classification rules living in pipeline/classify.py.
Legal basis is derived strictly from Title 14 CFR citations (91.137, 91.141, 91.143, 91.145, 99.7). Every classification records an evidence phrase and confidence score.
4. Geospatial Resolution
Center coordinates and radii are converted into closed 64-point polygons. Point-in-polygon and haversine algorithms resolve each restriction to its containing state, county, nearest city, and all affected public and private airports inside the boundary or within 10 nautical miles.