Proposal: Projection Attribute Extension for Zarr v3

attributes/geo/proj/README.md

@@ -0,0 +1,28 @@
+# Geo Projection Attribute Extension for Zarr
+
+- **Extension Name**: Geo Projection Attribute Extension
+- **Version**: 0.1.0
+- **Extension Type**: Attribute
+- **Status**: Proposed
+- **Owners**: @emmanuelmathot
+
+## Description
+
+This specification defines a JSON object that encodes datum and coordinate reference system (CRS) information for geospatial data stored under the `proj` key within the `geo` dictionary in the attributes of Zarr groups or arrays.
+
+## External Specification
+
+The complete specification, including detailed documentation, JSON schema, examples, and implementation notes, is maintained in the [EOPF Data Model repository](https://github.com/EOPF-Explorer/data-model/tree/main/attributes/geo/proj).
+
+**Repository**: https://github.com/EOPF-Explorer/data-model  
+**Specification Path**: `attributes/geo/proj/`
+
+## Quick Reference
+
+- **Recommended usage**: Store CRS-encoding JSON object under the `proj` key in the `geo` dictionary of group `attributes`
+- **Inheritance**: Group-level definitions apply to direct child arrays; array-level definitions override group-level
+- **Key fields**: `version`, `code`, `wkt2`, `projjson`, `bbox`, `transform`, `spatial_dimensions`
+
+## License
+
+This attribute extension is licensed under the [MIT License](https://opensource.org/licenses/MIT).