The FlatGeobuf community has started the process to formally adopt the specification as an OGC Community Standard. (A document linked by Bert Temme on Twitter, providing reasoning for the spec to become a standard, is not publicly available anymore.)
FlatGeobuf provides binary encoding for geospatial vector data. It is lossless, streamable, enables random feature access, and is supported by a wide range of geospatial tools and libraries, including QGIS, GDAL, Fiona, and PostGIS.
OGC Community Standards are developed outside the more formal OGC standardisation process, usually by a group of individuals who also implement reference solutions (instead of panels of representatives from large organisations).
PMTiles version 3 introduces a new tile-addressing schema. Instead of using Z,X,Y tile coordinates, the new schema uses tile IDs based on the tile’s position within a series of Hilbert curves:
The TileId 36052 corresponds to the Z,X,Y position of 8,40,87. The calculation of ID uses a pyramid of Hilbert curves starting at TileId=0 for zoom level 0. The next zoom level, a 2x2 square, occupies the next four IDs in the ID space TileId=(1,2,3,4), the next level being the next 16 IDs, and so on.
And to not duplicate tiles that contain virtually no information (for example, tiles just showing water) the RunLength indicates how many times a tile will be repeated within the Hilbert curve, so vast areas of the ocean can be represented with just one tile.
Ocean tiles are not only repetitive, but sparse and often contiguous in Hilbert space. This entry:
Zarr originated in genomics research but has since been adopted by the geospatial community because of its ability to quickly access multi-dimensional data in chunks. Zarr allows accessing a window of its data without having to first download the entire data set and dissect it locally. Think of a thirty-year time series of a grid of ocean-surface temperature data, where you can just retrieve the area around the Canary Islands for the last three years.
Zarr data can be stored in a wide range of storage systems, including object stores, such as AWS S3 or Google Cloud Storage, or in storage accessible via HTTP APIs. This makes Zarr the ideal candidate for cloud-native storage and processing of large, multi-dimensional datasets.
Community standards are a way for the OGC to formally adopt specifications developed outside the OGC standardisation process. A community-standard endorsement signifies that a specification is mature, established, widely used, and implemented into reference software. This is a big step for Zarr 2.0, showing that it is now a de-facto way to access multi-dimensional data sets over the Web.
A community standard usually represents a snapshot of a specification under constant development. The Zarr community already works on advancements to the existing standard, eventually resulting in a new Zarr 3.0 specification and proposed to the OGC as a new community standard. Other work includes an extension to the Zarr 2.0 specification formilising how georefrenced grids should be represented in Zarr.