GeoZarr SWG Monthly Meeting, 1 April 2026

Meeting Purpose

Review progress, resolve community issues, and align on the GeoZarr roadmap.

Key Takeaways

• CF alignment is GeoZarr's biggest challenge. Two paths are emerging: a conservative NCZarr-style mapping of existing CF structures versus a semantic-first approach that re-evaluates 30-year-old assumptions. This will be a V2+ effort.
• V1 release candidate still targets May. The timeline is contingent on GDAL 3.11, scheduled for May 4, which will provide critical implementation support.
• New semantic layer proposed. A 2-pager on integrating the I-ADOPT ontology will be drafted for the next meeting to address the limitations of CF's monolithic standard names.
• Helsinki meeting is a key opportunity. A joint session with other OGC SWGs/DWGs (OMS, TimeseriesML, MetOcean) is planned to coordinate work on describing observational data.

Topics

Community engagement and process

• Website as central hub. geozarr.org is now the primary source for meeting info, replacing scattered HackMD links.
• OGC Agora integration. A pinned post will be created linking to the website to improve discoverability for OGC members.
• Meeting notes access. A broken link on the website was fixed; notes are now viewable.
• Calendar invite. The outdated HackMD link will be updated.

CF convention alignment

• Problem. How to map CF conventions to Zarr. A recent CF governance panel meeting was inconclusive, leaving two main approaches.
• Approach 1, conservative mapping (NCZarr-style).
  • Proponents: Unidata and the NetCDF community.
  • Method: Straightforward mapping of existing CF structures (e.g., NCZarr for Zarr v2) to Zarr v3.
• Approach 2, semantic-first re-evaluation.
  • Proponent: Patrick.
  • Method: Revisit 30-year-old CF assumptions (e.g., spherical Earth, time precision) to create a more modern, Zarr-native encoding.
  • Goal: Maintain semantic compatibility with CF, not encoding-level backwards compatibility.
  • Status: A draft convention will be shared on GitHub before the next meeting.

Advanced semantics (I-ADOPT)

• Problem. CF's monolithic "standard names" are a closed shop and don't provide the rich, atomized semantics needed for terrestrial monitoring data (e.g., water quality, soil).
• Proposed solution. Integrate the I-ADOPT ontology to disaggregate observable properties into distinct, resolvable concepts (property, object of interest, matrix, procedure).
• Action. Kathi will draft a 2-pager on how to integrate I-ADOPT into the GeoZarr model for the next meeting.

V1 release and implementation readiness

• V1 release candidate target: May 2026.
• Key dependency: GDAL 3.11, which includes GeoZarr support.
  • Scheduled release: May 4, 2026.
  • Decision: The May 6 meeting will evaluate whether the GDAL release is stable enough to proceed with the V1 RC timeline.
• Multiscales convention enhancement.
  • Problem: Implementations needed to parse the shard codec to find read chunk sizes, which is inefficient.
  • Solution: Max will open a PR this week with a proof-of-concept to add read tile size information directly to the Multiscales convention.

Governance and OGC coordination

• OGC IP clause. Max will meet with Scott and Greg to resolve the IP clause's interaction with the GitHub repo structure.
• Co-chair invitation. Max invited an OGC member to co-chair to ensure meeting continuity.
• Voting process. Chris outlined OGC voting rules, including charter members, quorum (e.g., 1/3 of voters), and proxy assignments.
• Helsinki meeting (June 2026).
  • Goal: Coordinate a joint session with other SWGs/DWGs (OMS, TimeseriesML, MetOcean) to avoid scheduling conflicts and present a unified approach to observational data.
  • Action: Max will request a GeoZarr session using the forms posted by Scott Simmons.

Next Steps / Action Items

• Max
  • Create a pinned post on OGC Agora linking to geozarr.org (with the meeting-minutes link).
  • Fix the SWG meeting-minutes link on geozarr.org.
  • Update the HackMD link in the recurring calendar invite.
  • Schedule the meeting with Scott and Greg on the OGC IP clause.
  • Assign Wietze as reviewer on the implementation-criteria PR.
  • Open a PR to add a "Notes" section to the implementation criteria; tag Manuel.
  • Confirm the R library details action item and update notes.
  • Open a PR and POC enhancing the Multiscales convention with read tile size info; share on GitHub and Agora.
  • Request a GeoZarr session for the Helsinki meeting.
• Kathi
  • Draft a 1 to 2-page proposal on integrating CF / I-ADOPT semantics into GeoZarr for the next meeting.
  • Coordinate with Max on the joint Helsinki session; share the list of groups and contacts.
• Patrick
  • Share the draft CF-aligned, n-dimensional coordinate-system GeoZarr convention on GitHub before the next meeting.
• Wietze
  • Review the PR on implementation criteria.