Metrics

EVI (Ecological Volume Index)

A proxy for coral biomass — volume in cm³ computed from L × W × H field measurements.

A proxy for coral biomass — the 3D volume of a fragment or colony in cm³. Used alongside health and bleach scores to track growth over time.

Field input: Gardeners record three linear measurements — length (L), width (W), and height (H) — as prescribed for nursery and mother colony monitoring in the methodology.

Computation: EVI is derived in the ReefOS Data API as a cylindrical approximation:

$\text{EVI} = \pi \cdot r^2 \cdot h \quad \text{where} \quad r = \frac{L + W}{4}$

Values are discarded when the L/W/H ratios fall outside [0.1, 10] — a sanity filter for input errors.

Methodology note: The 2025 Methodology Manual prescribes recording L × W × H for mother colonies and growth-monitored fragments. The name "EVI" and the cylindrical formula are operational — they live in the ReefOS Data API (add_evi() in compute_statistics.py) and are stored in the _statistics collection.