Is Zarr the new COG?

Cloud-Optimized GeoTIFF (COG) and Zarr have each earned their place in modern geospatial workflows. While often framed in opposition—raster vs. analysis, imagery vs. data cube—they are in fact deeply complementary. In this talk, we’ll unpack how they address similar challenges from different angles, and why they should be considered parts of a shared toolkit rather than competing paradigms.

We’ll highlight where Zarr and COG overlap, where they differ, and how decisions around chunking, compression, tiling strategies, and metadata design affect both formats. We’ll discuss implementation pitfalls, emerging best practices, and the still-unanswered questions that data producers and tool builders face.

More than a comparison, this talk is a call to action: the community lacks clear guidance and consistent support for practitioners working to produce data in either format. We’ll highlight concrete gaps in the tooling landscape, share ideas from our own work on how to improve decision-making and best practices, and invite others to collaborate on building a healthier, more cooperative open geospatial data ecosystem.