Web-optimized Zarr

Web-optimized zarr provides a set of additional recommendations on top of the GeoZarr specification for optimal browser-based analysis and visualization. The specific recommendations are still under development. We anticipate the following to be included as web-optimized Zarr recommendations:

  1. The WOZ MUST be chunked in the spatial and/or temporal dimensions. The WOZ guide will include a reference to a separate document for recommended chunking schemes and compression algorithms for different use-cases, which will be updated as browsers and infrastructures change.
  2. The dimension order for 2-dimensional data MUST be (y, x) (or the equivalent spatial dimension names) for maximum interoperability.
  3. The dimension order for 3-dimensional data MUST be (time, y, x) (or the equivalent spatial dimension names) for maximum interoperability.
  4. The WOZ MUST include multi-scales.
  5. The WOZ may contain full-resolution “archival” versions in other file formats and reduced resolution versions in “native” zarr.

The following criteria may be included after further evaluation:

  1. The multi-scales must align with a well-known TMS.
  2. The WOZ should include sharding to allow clients to request smaller individual chunks or larger shards.
  3. The multi-scales should contain rendering metadata (e.g., min and max values and preferred color mapping representations).

These recommendations will be expanded or updated after additional experimentation.

For a graphical depiction of how WOZ compares to GeoZarr, please see the excalidraw diagram.