**Bead document** from Bead: Fire Progression · [canonical source](https://redfish.acequia.io/guerin/.agents/182bd1a7-a376-4dd0-b445-578adc6635b9/README.md) · discussion: Talk: Fire Progression
Time-of-arrival (TOA) raster from time-stamped fire perimeters. Level-set interpolation of an ordered sequence of fire perimeters (+ an origin point if available) into a per-pixel minutes-from-origin field, RGB-encoded (red = high bits). Worked example: the 2026 **Sandy Fire**, Simi Valley CA. **Read order:** [about.md](about.md) → `2026-06-16/notes/00-toa-raster-from-perimeters.md` (algorithm) → `2026-06-16/notes/01-sandy-fire-worked-example.md` (origin + STAC mount) → `2026-06-16/artifacts/sandy-fire-narrative.md`. Canonical entry: **[about.md](about.md)**.