snow-hokkaido data

Daily, cloud-aware snow-cover records for Hokkaido, built from Sentinel-2 L2A on a z18 XYZ-tile cell grid (112 m cells). Code, documentation and the dashboard: https://github.com/dwg7/snow-hokkaido

Layout

• obs/season=YYYY/<JST date>/<datatake_id>.tif obs-lite, one COG per pass: band 1 class (0 not scanned, 1 cloud, 2 shadow, 3 green = clear and no snow, 4 snow), band 2 clear_pct. EPSG:3857, z18 cells, 7168 x 4608 cells (z9 tiles x 454..467, y 183..191). Not every pass covers all of Hokkaido: uncovered cells are 0.
• events/ per municipality and pass: counts of cells by class (Parquet)
• derived/state/ per municipality and date: last-known state counts (Parquet)
• derived/daily/ per municipality and observed day: counts of that day's observation (one observation per cell per day; same columns as events)
• pixel/season=YYYY/latest.tif latest cell ledger (6 bands, uint16); a cache that can be rebuilt from obs
• view/ raster PMTiles for the dashboard (z4-z10; a z10 pixel is a cell) and dates.json

Municipality boundary geometry is not included. Rebuild the cell-to-municipality map yourself (just fetch-n03, just cellmap in the repository).

License and attribution

CC BY 4.0. Please credit:

• Contains modified Copernicus Sentinel data 2026 (Sentinel-2 L2A, via Earth Search by Element 84).
• Municipality codes and aggregation use 「国土数値情報(行政区域データ)」(国土交通省) (https://nlftp.mlit.go.jp/ksj/gml/datalist/KsjTmplt-N03-2026.html) as the basis; the data were processed (assignment to cells, aggregation). This is not a product made by the national government.
• Snow classes are provisional (algorithm version in each file's tags); see the repository's docs/stage1-checks.md for what was and was not verified.