isochrone

Live: iso.huseyincapan.dev

Click anywhere on the map and see the street network you can actually reach on foot within 15 minutes — coloured by arrival time, with mobility profiles that account for stairs and unpaved paths.

OSM data → PostGIS + pgRouting → Express → Leaflet.

How it works

pgr_drivingDistance walks the street graph from the vertex nearest your click until the time budget runs out, and returns every reachable edge with its arrival time. Those edges are grouped into 10 equal time bands and drawn directly — no hull, so the map shows the streets you can reach rather than a blob implying you can cross the middle of a block.

Edge cost is length / speed in seconds, computed per request from the selected profile, so a profile is a few numbers rather than a schema change:

These factors are estimates, not measurements — see Calibration below.

Ask Claude about it (MCP)

The isochrone-mcp package lets any MCP client answer reachability questions against this API:

claude mcp add isochrone -- npx -y isochrone-mcp

One tool, reachable_area: origin + minutes + profile, optional target ("can I get there in time?"). Returns a prose summary and a map link, not coordinate soup. Details in mcp/.

Dev

Needs Postgres (PostGIS + pgRouting) on 5454 and Redis on 6363:

docker compose up -d db redis

Import a city (needs osm2pgrouting, osmium-tool and libpq on PATH — export PATH="/opt/homebrew/opt/libpq/bin:$PATH" on macOS):

cd overpass/osm-imports && ./import_city.sh germany berlin

Then:

cd isochrone-backend && npm i && npm start   # :3001
cd isochrone-ui && npm i && npm run dev      # :5173, proxies /api

Deploy

cp .env.example .env      # change PGPASSWORD, set SITE_ADDRESS
docker compose up -d --build

Caddy terminates TLS on 80/443 (automatic Let's Encrypt once SITE_ADDRESS is a real hostname), compresses responses, and proxies to the app — which serves the API and the built UI together, so there's no separate web server. The app port is not published; it is reachable only through Caddy. Postgres and Redis bind to 127.0.0.1 so the import script works from the host without exposing them publicly.

CITY selects which schema to query and must match the imported one (import_city.sh greater-london creates schema greater_london).

Getting a city into the deployment

The database starts empty. Rather than running osm2pgrouting on the server — which needs osmium, a 1.6GB intermediate file, and a long import — dump the schema from a machine that already has it and restore:

pg_dump -h 127.0.0.1 -p 5454 -U postgres -d osm_db \
  --schema=berlin -Fc -Z6 -f berlin.dump          # ~105MB, ~10s

# on the target, extensions first — a --schema dump doesn't carry them
psql -h 127.0.0.1 -p 5454 -U postgres -d osm_db -c \
  "CREATE EXTENSION IF NOT EXISTS postgis;
   CREATE EXTENSION IF NOT EXISTS pgrouting;
   CREATE EXTENSION IF NOT EXISTS hstore;"

pg_restore -h 127.0.0.1 -p 5454 -U postgres -d osm_db \
  --no-owner -j4 berlin.dump                       # ~5s

Berlin restores to ~587MB (the source schema is larger only because of dead tuples from the cost UPDATEs). The db image is pinned to the major version the dump came from — a dump will not restore into an older Postgres.

Verifying a deployment

API=https://iso.example.com node scripts/check.mjs

Checks

node scripts/check.mjs     # needs the backend running

Asserts every time band comes back and that reach is non-increasing across walk → stroller → wheelchair.

Warming the cache

scripts/precompute.ts and the RabbitMQ producer.ts/worker.ts pair drive the backend over HTTP rather than reimplementing the routing SQL, so they can't drift out of sync with it. Live queries are ~0.4s, so this is only worth running for a city-wide sweep.

Known gaps

• Graph islands. The vertex nearest a click can sit on a disconnected fragment — 52.515,13.400 reaches 13 nodes. Fix is a one-time pgr_connectedComponents table for the vertex lookup to join against.
• Calibration. The speeds above are guesses. Google's Isochrones API (Preview) supports WALK and returns GeoJSON, so the walk profile could be calibrated against it. It has no stroller/wheelchair mode, so those stay unvalidated.
• Stranded origins render as a tiny blob rather than saying "unreachable with this profile".