Processing and methodology
The workflow begins with reviewed source data and a selected marine area. It builds canonical water support, processes independent feature families, validates candidate products, then optionally promotes an audited release. Workflow operations describe command effects; scientific contracts define the output obligations.
Spatial support and units
- H3 R8 model-area cells have nonzero water overlap. R6 is the exact parent union of those R8 cells, including possible hierarchy-only parents. Full H3 geometry, water-clipped geometry, and model-area support have different meanings.
- Geographic source data and projected measurements retain declared CRS and vertical datum. Planar meter/area calculations reject geographic or non-meter projected axes.
- Bathymetry uses an explicit positive-down depth convention where configured. A source elevation value must not be silently treated as depth.
- Different products use different neighborhoods: direct pixel-to-H3 assignment, water-connected graph paths, configured metric distances, or source inventory overlays. A common H3 key does not make their support identical.
How representative products are made
| Product | Processing choice | Consequence |
|---|---|---|
| Bathymetry R8/R6 | Valid native marine raster pixel centers are assigned directly to each requested H3 resolution for all statistics, counts and depth bands. | A hierarchy-only R6 parent with no direct sample stays null. Native pixel spacing is not improved by H3 reporting. |
| Native-raster slope | Land/nodata are masked before finite differences; interior central differences need valid neighbors, edges use one-sided differences. | Coastal or nodata-adjacent slope support can be absent; the method is not a geodesic derivative. |
| H3 terrain curvature | A quadratic fit uses the H3 center and water-connected neighbors in a metric CRS, requiring a full-rank design. | Curvature and aspect can be undefined on flat or insufficient support; retain method-versioned signs and QC. |
| Shoreline character | Mapped segments are classified only when source labels support the class; fractions divide by classified length. | Unclassified length changes coverage and does not mean no shoreline. Overlapping classes need not sum to one. |
| Geometric fetch | R8 straight-line rays follow 16 bearings up to a configured limit. | A ray reaching the limit is censored, and fetch is not wind or wave exposure. |
| Substrate | Modeled dbSEABED rock presence and CoDA sediment texture are kept separate. | A point sample cannot establish areal coverage; unsupported fractions remain null. |
| Habitat evidence | Source footprints and survey opportunity are carried separately from mapped positives. | A positive-only map does not establish surveyed absence; R6 aggregation recomputes evidence by child water area. |
These are summaries of implemented methods, not substitutes for the seafloor guide, coastal guide, and family source notes. They state method versions and caveats in greater detail.
Missingness, provenance, and publication
Unknown, unavailable, disconnected, unmapped, not applicable, and observed zero remain distinct. A null value must be read with its coverage/QC or status field and denominator. Source vintage, acquisition/build timestamps, configuration and code identity, manifests, and checksums support reproducibility. Candidate products are isolated; a completed schema-3 release is addressable by an immutable release ID. The public API resolves exact product/resolution artifacts and validates checksums.