A mapping team uses the populated-places layer to label its world basemap and has been told the labels 'miss whole cities'. Before spending on a bigger gazetteer, the team lead wants the claim measured: of the urban footprints that are big enough to matter — a thousand square kilometres and more — how many have no place point inside them at all, and how much built-up area that is. A gap that big is a city with no name on the map.
Return the urban footprints of at least 1,000 km² (area on the ellipsoid, or in an equal-area projection) that contain no populated place, as polygons carrying:
urban_idarea_km2 — the footprint's area, 1 decimalA footprint counts as covered when at least one place point falls inside it. Return the uncovered ones only, in EPSG:4326, largest first.
These are where the teaching is. Read them twice.
Completeness of one layer against another is how a mapping team decides whether its labels, addresses or facility lists are fit for a market before it buys more data.
5 scored, 0 informational
How many large footprints have no place inside
36%Carries urban_id and area_km2
18%Total footprint area of the uncovered set
27%Result is polygons
9%Submitted in EPSG:4326
9%