An illustrative humanitarian logistics desk needs an initial access screen for national capitals. It compares nearby civil airfields and ports to identify places whose route needs direct verification. A straight-line distance cannot establish road travel, port capacity, airfield condition or permission to operate; the output is a question list for the response team, not an operational route plan.
Use the supplied /data/places.geojson, /data/airports.geojson and /data/ports.geojson point layers in EPSG:4326. The fields used are capital, name and country on places; type on airports; and geometry on all three. Return the capital point geometry and the properties name, country, airport_km, port_km and mode in EPSG:4326. The distances are great-circle kilometres to the nearest eligible facility, rounded to one decimal in the delivered result. Eligible airfields have a type of major, mid, major and military or mid and military. The mode labels are illustrative screening categories, not a claim about actual access.
Three stages.
Stage 1 — Air. For every national capital (capital = true), the great-circle distance to the nearest civil mid-size or major airport — type in major, mid, major and military, mid and military — as airport_km.
Stage 2 — Sea. For every capital, the great-circle distance to the nearest port as port_km.
Stage 3 — Mode. Assign each capital a mode by these rules, in this order:
| rule | mode |
|---|---|
airport_km ≤ 75 | air |
otherwise port_km ≤ 75 | sea |
otherwise airport_km ≤ 500 | road |
| otherwise | unreachable |
Return only the capitals whose mode is not `air` — the exceptions the director needs to see — as points carrying name, country, airport_km, port_km (one decimal) and mode. Distances are global, so they are geodesic; no single projected CRS is right from Reykjavík to Funafuti.
These are where the teaching is. Read them twice.
Modelled on the Logistics Cluster, Venezuela Earthquake Response Situation Report #1 (2026, https://logcluster.org/en/documents/venezuela-respuesta-terremotos-reporte-situacional-1-2-julio-2026), which reviews airports, ports and ground access separately and calls for capacity verification. This global capital screen uses illustrative distance cutoffs; it does not reproduce that response or assert any facility is operational.
6 scored, 0 informational
How many capitals are not served by air
31%Capitals returned as points
8%Carries name, country, airport_km, port_km and mode
15%The longest airport leg in the set
15%Sum of the port distances across the set
23%Submitted in EPSG:4326
8%
