The observer's body
Biometric data from the artist's activity tracker, read alongside the sea. Four time-scale layers applied to a human body: fast (last 2 hours), diurnal (this hour vs past 14 days), slow (daily values over 30 days), baseline (personal mean ± std). The layers accumulate as the system runs.
Today
Daily summary fetched from Garmin Connect — resting heart rate, sleep score, body battery, stress, steps, SpO2, HRV. One value per day per metric.
Fast layer
Heart rate, stress, and body battery at sub-hourly resolution — the last 2 hours of intraday readings. Detects the body's current rhythm: is the pulse climbing right now, is stress releasing, is energy draining?
Diurnal layer
Same hour of day across the past 14 days. Asks: is the body at this hour today unusual compared to this hour recently? A tired afternoon, a restless morning — revealed by comparing like-with-like rather than against daily averages.
Slow layer
Daily values over the past 30 days. Detects multi-week trends: is resting HR gradually rising? Is sleep quality declining? Is body battery consistently low? Accumulates over time — more meaningful as more days are collected.
Baseline
Personal mean and standard deviation computed from all available history. What is normal for this specific body — not population averages. The baseline updates as more data accumulates. A reading is salient when it deviates from this personal norm.