Document reference implementation

[maxrjones]

Summary

Formally document eopf-geozarr as the reference implementation for GeoZarr conventions, providing implementation notes, conformance claims, and guidance for other implementers.

Background

The charter (Section 4) states that "reference implementations that fully use GeoZarr should be documented at the same time the candidate Standard goes to vote."

eopf data-model (v0.8.0) implements all three conventions and can serve as the reference implementation. This needs to be formally documented.

Acceptance Criteria

• Reference implementation status declared
• Conformance claims documented per class
• Implementation notes for each convention
• Known limitations documented
• Test coverage reported
• API stability commitment
• Link from main spec to reference impl

Documentation Structure

1. Conformance Statement

## eopf data model Conformance Statement

**Version:** 0.8.0
**GeoZarr Version:** 1.0 (draft)

| Conformance Class | Status | Notes |
|-------------------|--------|-------|
| GeoZarr Core | Conformant | |
| geo-proj | Conformant | Supports EPSG, WKT2, PROJJSON |
| spatial | Conformant | Affine transforms only |
| multiscales | Conformant | Power-of-2 downsampling |

2. Implementation Notes

geo-proj Implementation

• How CRS is stored and retrieved
• PROJJSON generation from pyproj
• Inheritance implementation details

spatial Implementation

• Affine transform handling via rasterio/Affine
• Dimension ordering conventions
• Grid registration handling

multiscales Implementation

• Downsampling algorithm (averaging)
• Level naming convention
• Transformation calculation

3. Known Limitations

4. For Implementers

Guidance for others implementing GeoZarr:

• Required dependencies
• Key design decisions and rationale
• Common pitfalls
• Test cases to verify conformance

Files to Create/Update

• geozarr-spec/implementations.md - Registry of implementations

Implementation Registry

Create a registry of known implementations. Per the Zarr Conventions Framework, reaching Candidate maturity requires 3+ implementations, and Stable requires 6+.

Implementation	Language	Maintainer	geo-proj	spatial	multiscales
eopf-geozarr	Python	ESA/Spacebel	Full	Full	Full
zarr-cm	Python	GeoZarr SWG	Full	Full	Full
geozarr-examples	Python	GeoZarr SWG	Full	Full	Full
rioxarray	Python	Corteva	In progress	In progress	None
GDAL	C++	OSGeo	Planned	Planned	Planned
OpenLayers	JavaScript	OpenLayers	Read	Read	Read
TiTiler	Python	Development Seed	Read	Read	Read

Current implementation count: 6 (3 full, 1 in progress, 2 read-only)
Target for Candidate: 3+ ✓
Target for Stable: 6+

Tracking

Emmanuel Mathot will track implementation status of Spatial, Proj, and Multiscales conventions and report at SWG meetings.

Dependencies

• Define conformance classes structure #108 (Conformance classes must be defined)
• Test suite for conformance verification

Notes

• Coordinate with eopf data model maintainers
• Consider creating a conformance badge/logo
• Plan for updating as implementation evolves