Cells covered by each zone, on a given grid

The (zone × grid) intersection — which is a function of geometry and grid alone, not of any release. score_zones.qmd recomputes it per version, so the six releases sharing programarea_2026-03 each paid for the same exactextractr pass; keyed on (zone_set_key, grid_id) it is computed once.

Usage

zone_cells(ply, cellid_tif, key_col)

Arguments

ply

an sf of zone polygons

cellid_tif

path to that grid's cell-id COG

key_col

column of ply holding the zone key

Value

a data frame with zone_key, cell_id, pct_covered (1-100)

Details

Reads the grid's cell-id COG, whose pixel VALUES are cell ids (a lookup image — see grid.R), so the returned ids are in that grid's id-space whatever frame the raster itself uses.

Semantics deliberately match the per-version implementation this replaces, so relocating it cannot move any score: coverage is rounded to whole percent and anything rounding to zero is dropped.