GLACE mosaics – agent guide

One item per year on a fixed ETRS89-LAEA (EPSG:3035) grid at 40 m. Twelve analysis rasters per year and fourteen PMTiles archives beside them, which are what drawing uses.

The grid is the point

Every year shares one fixed extent, resolution and transform. Two things follow, and both are what this collection exists for:

1. Temporal stacking is free. No reprojection, no alignment, no resampling.
2. Areas are pixel counts. The grid is equal-area, so summing pixels gives an area without a latitude correction. Do not do this on a Web Mercator raster.

Drawing versus reading

Two products, and they are not interchangeable.

PMTiles, {stem}_viz.pmtiles in each year's item directory, are what a map client uses. Each one is an asset of that item with the visual role and a rel: "pmtiles" link on this collection, and each year has its own MapLibre style as a style-{year} asset under styles/; the latest year's also carries the default role. Their pixels are 8-bit display codes under a fixed stretch, and the backscatter and quality-map archives are in decibels while every raster in this catalog is linear. They are renderings. Never read one for a value.

The COGs carry the measurements. The renders block declares the stretch, the ramp and the decibel expression, so a client can colorize them at draw time and get the same picture with the numbers still underneath.

Rendering parameters

Every stretch is fixed across years and was measured on the published display mosaics (2 to 98 % over 2021–2024). The archives bake these; the renders block declares the same numbers with portable colormap names, which any titiler-compatible client accepts verbatim:

Related

The tiles collection is the archive these are derived from: same measurements at 10 m in each square's own UTM zone, one item per (square, year). A mosaic year matches the tile items with the same datetime; reproject before comparing pixels, since the tiles are in UTM and the mosaics in LAEA.