Reachable area (isochrone)
isochroneRead-onlyIdempotent
Calculate the area reachable from a point within a given time budget for walk, cycle, or drive modes. Enter coordinates or a place name to receive a polygon of accessible streets.
Instructions
Isochrone: the area reachable from a point within minutes, by mode.
Give the point as lat/lon, or as `where` — a {"lat", "lon"} dict, a
GERS id, or a free-text place name — but not both (and not neither);
either way returns {"error": "bad_request"} naming the choice. A
`where` given as an id/name adds a compact "resolved": {"name", "id",
"lat", "lon", "matched_by"} to the answer; absent for lat/lon or a
{lat,lon} where.
Builds a street graph from Overture's transportation theme and runs
Dijkstra out to the time budget. Each mode
excludes its own set of unusable road classes (e.g.
drive excludes footway/path/steps; cycle and drive exclude
motorway/trunk... drive itself allows motorways) and respects one-way
restrictions for cycle/drive (walk ignores them). speed_m_s overrides
the mode's default speed model (walk 1.4 m/s, cycle 4.2 m/s, drive
per-edge from Overture's speed_limits or a class-based default table)
with a single constant. Returns {"polygon": <GeoJSON Polygon>, "stats":
{reachable_nodes, max_radius_m, area_km2}, ...}. The polygon traces the
boundary of reached nodes' occupied grid cells (falling back to a
convex hull for very small reachable sets); reachable_nodes/
max_radius_m are always exact, only the drawn polygon shape
approximates, and is decimated/simplified to fit the token budget.
radius_m optionally overrides the auto-derived graph extraction radius
(capped per mode: 5km walk, 15km cycle, 60km drive); passing something
larger than the cap returns a structured error instead of silently
truncating. An unrecognized mode string returns a structured
{"error": "unsupported_mode"}. minutes must be > 0 and radius_m (if
given) must be >= 0, else returns {"error": "bad_request"}.
Input Schema
TableJSON Schema
| Name | Required | Description | Default |
|---|---|---|---|
| lat | No | ||
| lon | No | ||
| mode | No | Travel mode. Default: stored preference, else walk. | |
| where | No | ||
| minutes | No | ||
| radius_m | No | ||
| speed_m_s | No |
Output Schema
TableJSON Schema
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||