Glossary

Plain definitions for the terms that show up in the Submarius docs and API responses. If something here is wrong or unclear, please open a methodology question.

A

ABI — Advanced Baseline Imager. The instrument on NOAA’s GOES-16 satellite that takes the visible/infrared imagery Submarius processes into hourly water-colour data.

ACOLITE — An open-source atmospheric-correction processor for satellite imagery, originally developed for Sentinel-2 and Landsat, extended to GOES. Submarius uses it to extract ocean-colour signal from raw GOES-16 ABI L1b radiance. https://github.com/acolite/acolite

Adjacency effect — In satellite ocean colour, the bias caused by land or shallow-bottom reflectance bleeding into the signal of an adjacent water pixel. Pushes apparent clarity higher than reality. Submarius downweights affected pixels.

AOT — Aerosol Optical Thickness. Measured by satellite to distinguish atmospheric haze from water-leaving radiance.

B

Bathymetry — The underwater equivalent of topography: depth of the seafloor as a function of position. Submarius uses GEBCO bathymetry to cap visibility estimates (you can’t see past the bottom).

Bite score — Submarius’s 0–10 fish-activity index for a target species at a location and time. See features/bite-score.md.

C

Case-1 / Case-2 — An oceanographic classification of water type. Case-1 is open ocean dominated by phytoplankton; Case-2 is coastal water dominated by suspended sediment, CDOM, and river-borne material. The Lee 2015 Kd→Secchi coefficient differs between them. See methodology/kd490-explained.md.

CDOM — Coloured Dissolved Organic Matter. Tannin-like dissolved organics that absorb blue light and tint water yellow-brown. Common in river-influenced coasts, mangrove systems, and tannic regions like the Carolinas and northern Australia.

Chlorophyll-a — Pigment in phytoplankton; satellite-measurable proxy for phytoplankton biomass. Used by Submarius for water-type classification (high chlorophyll → bloom-influenced → leans Case-2).

CoastWatch — NOAA’s satellite ocean-colour and SST data programme. Distributes the VIIRS-SNPP and multi-mission DINEOF products Submarius consumes.

D

DINEOF — Data Interpolating Empirical Orthogonal Functions. A gap-filling technique used by NOAA to produce continuous Kd490 fields from cloud-affected daily satellite data.

Diver-relevance horizon — Submarius caps clarity output at 122 m (400 ft) because most divers don’t go past that depth. Beyond it, visibility numbers are operationally meaningless.

E

Edge Network — Reverse-proxy CDN edge. Submarius doesn’t currently use one; mentioned occasionally in the docs context.

EnKF — Ensemble Kalman Filter. A state-estimation technique for combining noisy time-series observations with a forward physical model. Submarius’s clarity model uses point-estimate fusion today; EnKF integration is planned.

ERDDAP — Environmental Research Division Data Access Protocol. A NOAA data-server framework that exposes scientific data via uniform HTTP endpoints. Submarius pulls satellite Kd490 from CoastWatch’s ERDDAP instance.

F

FNU — Formazin Nephelometric Unit. A standard turbidity unit. USGS publishes river turbidity in FNU; we don’t currently use it directly in the clarity model but it’s available as an input signal.

Front (cold front) — A weather-system boundary; passage typically suppresses fish activity for 6–24 h, then often produces a 24–36 h rebound.

G

GEBCO — General Bathymetric Chart of the Oceans. Free global bathymetric grid used by Submarius for the depth cap and the bathymetry overlay.

GHRSST — Group for High Resolution Sea Surface Temperature. A NASA/NOAA-coordinated SST data product used by Submarius for the SST overlay.

GIBS — Global Imagery Browse Services. NASA’s tile-server for public satellite imagery; Submarius consumes the GHRSST tiles via GIBS.

GOES-16 — Geostationary Operational Environmental Satellite. A NOAA weather satellite parked over the Americas. Its ABI instrument provides the hourly imagery Submarius processes for sub-daily ocean colour.

H

H3 — Uber’s open-source hexagonal hierarchical spatial indexing system. Submarius uses H3 cells to (a) cache spatial data efficiently and (b) fuzz user spot locations for privacy. https://h3geo.org/

HAB — Harmful Algal Bloom. Submarius integrates NOAA’s Gulf Coast HAB Forecast for active-bloom severity, which both penalises the clarity estimate and surfaces a user-visible warning.

HRRR — High-Resolution Rapid Refresh. A NOAA 3 km surface weather model used by Submarius for the wind-particle overlay (Pro feature).

I

Inverse-variance weighting — The maximum-likelihood combination of independent observations with known variances. The mathematical backbone of Submarius’s multi-satellite Kd490 fusion.

IndexedDB — Browser-native client-side database used by Submarius for offline tile storage, conditions caching, and the mutation queue.

K

Kd490 — Diffuse attenuation coefficient at 490 nanometres. Measured by satellites; converts to Secchi depth via the Lee 2015 model. See methodology/kd490-explained.md.

L

L1b / L2 / L3 — Standard NASA/NOAA satellite-data processing levels. L1b = calibrated radiance; L2 = derived geophysical products at the original sensor resolution; L3 = gridded, time-averaged products.

Lee 2015 — The published mechanistic model for Kd → Secchi that underlies Submarius’s clarity computation. Lee, Z. P. et al. (2015), Remote Sensing of Environment 169, 139–149. R² = 0.96 against 338 in-situ measurements.

M

MapLibre — Open-source vector-map renderer used by Submarius. Fork of Mapbox GL JS.

MPA — Marine Protected Area. Submarius surfaces MPA boundaries from Protected Planet and the NOAA MPA Inventory.

N

NDFD — National Digital Forecast Database. NOAA’s authoritative gridded weather forecast.

NDBC — National Data Buoy Center. Real-time observational data from offshore buoys; Submarius consumes select NDBC stations for ground-truthing.

NODD — NOAA Open Data Dissemination programme. Distributes raw satellite L1b on AWS S3 (e.g. the GOES-16 ABI bucket Submarius processes).

O

OBIS — Ocean Biodiversity Information System. Authoritative species occurrence records used by Submarius for seasonal range modelling.

OCEARCH — Long-running shark-tracking research organisation; publishes the tagged-shark position feed Submarius surfaces in the shark-alerts feature.

OLCI — Ocean and Land Colour Instrument on the Sentinel-3 satellites. Component of the multi-mission DINEOF Kd490 product.

P

Plus Code — Open Location Code. A short alphanumeric code that uniquely identifies any 14×14 m square on Earth. Submarius surfaces Plus Codes alongside lat/lon for SOS and shared spots. https://plus.codes/

PWA — Progressive Web App. A web app installable like a native app, with offline support and push notifications.

R

Resuspension — Wind-driven re-mobilisation of bottom sediment into the water column. Major contributor to nearshore turbidity. Modelled in Submarius via the W²/H scaling from Green & Coco (2014).

S

Secchi disk / Secchi depth (Z_SD) — A 30 cm white disk lowered into water until it disappears from view. The depth at which it disappears is the Secchi depth. The classical standard for water clarity, and the unit Submarius reports.

SNPP — Suomi National Polar-orbiting Partnership. The satellite carrying VIIRS, the primary daily ocean-colour sensor for Submarius.

Solunar — Theory that fish activity peaks during specific lunar position windows (moon overhead, moon underfoot, moonrise, moonset). A component of the bite score; not load-bearing on its own.

SST — Sea Surface Temperature. Used by Submarius across the clarity model, the bite-score, and as a map overlay.

V

Verdict — Submarius’s per-day GO / NO / CAUTION output for the chosen activity at the chosen location. See features/verdict.md.

VIIRS — Visible Infrared Imaging Radiometer Suite. The instrument on Suomi NPP and JPSS satellites that produces the daily ocean-colour data Submarius’s clarity model is anchored to.

Viz / Visibility — Underwater visibility, in metres or feet. Approximated by Secchi depth.

W

WoRMS — World Register of Marine Species. Authoritative marine taxonomy and biology database; cached in Submarius for species data.

W²/H — Wind speed squared over water depth. The empirical scaling parameter for wave-driven sediment resuspension in shallow water.

Z

Z_SD — Secchi disk depth. See Secchi.