s102-bathymetry

name: s102-bathymetry description: | Expert knowledge of IHO S-102 Bathymetric Surface Product Specification (HDF5-encoded depth/uncertainty grids). Covers BathymetryCoverage groups, Group_F feature codes, depth/uncertainty dataset shapes, NODATA fill value handling (1,000,000f), tiling, georeferencing attributes, CRS conventions (often UTM), and the depth-shading portrayal palette. USE FOR: S-102 datasets, bathymetric grids, depth surfaces, uncertainty grids, HDF5 bathymetry, BathymetryCoverage, CoverageCell layout, depth shading, S102DatasetReader, S102CoverageSource, S102PortrayalCatalogue, PC-driven Lua portrayal, adding S-102 features, reviewing for S-102 spec compliance, RenderS102 tool changes. DO NOT USE FOR: S-104 water levels (use s104-water-level), S-111 currents (use s111-surface-currents), generic HDF5 access (use s100-framework).

S-102 Bathymetric Surface expert

When engaged

• Tasks touching src/EncDotNet.S100.Datasets.S102/**, tests/EncDotNet.S100.Pipelines.Tests/** for S-102 cases, or tools/RenderS102/**
• Changes to CoveragePipeline or ICoverageRenderer<T> that affect S-102
• New depth-shading palettes or coverage portrayal tweaks
• Map projection / CRS handling for S-102 grids

Spec anchors

• Canonical: S-102 Edition 3.0.0 Bathymetric Surface Product Spec
• S-100 Part 8: Coverages
• S-100 Part 10c: HDF5 encoding
• S-102 Annex A: Feature Catalogue
• S-102 Annex B: Portrayal Catalogue

Review checklist

1. HDF5 group/attribute names match the spec exactly (case-sensitive): /BathymetryCoverage/BathymetryCoverage.NN/Group_NNN/values, Group_F feature info, root attributes (eastBoundLongitude, westBoundLongitude, northBoundLatitude, southBoundLatitude, gridOriginLatitude, gridOriginLongitude, gridSpacingLatitudinal, gridSpacingLongitudinal, numPointsLatitudinal, numPointsLongitudinal, etc.).
2. depth and uncertainty are float32 compound dataset members; do not silently widen to float64 in the public API.
3. NODATA fill value is 1,000,000f (not NaN). Honor it via S102CoverageSource.FillValue → CoverageMetadata.NoDataValue and surface it through CoverageColorScheme.NoDataColor so the renderer paints fill cells with the active palette's NODTA token.
4. Grid origin is the node position of the first grid point, not a cell edge; bitmap extents need a half-cell pad.
5. Grid row 0 is the southernmost row; bitmaps draw row 0 at top — flip with rows - 1 - row when rasterising.
6. CRS may be UTM (EPSG:326xx); per-pixel reprojection is required for correct overlay on EPSG:3857. Do not stretch a native-CRS bitmap into a Mercator bbox.
7. Public API changes have xunit tests using SkippableFact for real HDF5 data.

Known pitfalls in this repo

• See /memories/repo/s102-viewer-notes.md for hard-won viewer alignment lessons (UTM reprojection, half-cell padding, fill value, row flip, ProjNet Transform return shape).
• Compound HDF5 datatypes via PureHDF need explicit struct mapping; field order must match the file, not the spec table.
• Multiple BathymetryCoverage.NN instances may exist (tiles); iterate rather than assuming a single coverage.