Glossary
Terms used across the docs and the API. Alphabetical. Cross-referenced where one definition depends on another. Use this page as a quick reference rather than reading it end-to-end.
Authority overlay
A category-specific arrangement where a single authoritative source (e.g. CQC for UK healthcare) is treated as primary, and competing low-confidence sources from POI providers are suppressed. See How POIs are built.
Cell
The small unit of geography a layer aggregates into. Two grids address cells here: H3 cells everywhere, and geohashes on the POI layers.
Cross-validated
A POI is cross-validated when two or more independent sources agree on its name and
location. Cross-validation is the difference between independent_source_count: 1 and
independent_source_count: 2. See How POIs are built.
data_version
The build timestamp of a per-country public-transport dataset (ISO-8601 UTC, e.g.
2026-08-06T14:16:11+00:00), surfaced by /v1/pt/meta. The POI dataset has no such field — its
equivalent signal is last_refreshed on /v1/stats. See Freshness.
ETag
A weak ETag header (W/"...") on cacheable responses. The API does not validate If-None-Match and never
returns 304, so read the token as a "has the snapshot rolled over?" marker. See
Freshness.
Foursquare Open Places
One of the three POI sources. Foursquare's freely-redistributable global places dataset. Strong on commercial venues. See How POIs are built.
Geohash
A rectangular grid cell from the geohash scheme, identified by a base32 string (gcpvj0)
whose length is its precision. Addresses the POI layers only. See
Geohash mode.
H3 cell
A hexagonal grid cell from Uber's H3 spatial indexing library. Cells are identified by a
hex string (89195da498fffff) and exist at multiple resolutions. Used throughout
Data API as the canonical "small unit of geography" for aggregating POIs, polygons, and
transport into queryable cells.
Isochrone
The set of H3 cells reachable from a starting point within a travel-time budget, under a
given travel mode. You compute this yourself by calling the sibling TravelTime Routing
API's h3-fast endpoint with your Routing API credentials, then pass the cell ids it returns
to any /v1/h3/* layer as cells, a list of hex strings. Data API does not provide an
isochrone API.
min_sources
Query-parameter filter on POI-returning endpoints. Values 1, 2, or 3 — tightens the
consensus floor to independent_source_count >= N (the echo-aware count). Higher values
trade recall for precision.
Authoritative-source POIs (TravelTime public transport for transport categories; gov
sources for healthcare, schools, etc. when those ship) pass any min_sources value —
authority is the consensus signal. See How POIs are built.
OpenStreetMap (OSM)
One of the three POI sources. The volunteer-edited geographic database. Strong on community-knowledge categories. See How POIs are built.
Overture
One of the three POI sources, and the source for polygon land cover. The Linux Foundation's federated maps project. See How POIs are built and How green space is built.
POI
Point of interest. A place with a name, location, and category. See How POIs are built.
Polygon
A geographic shape representing an area on the ground (a park, a forest, a recreation ground). Stored as H3-cell aggregates rather than as raw polygon rows. See Green space and polygons.
Precision
Geohash precision — the length of the geohash string, and so how fine the grid is. Two ship:
6 (~1.2 km) and 7 (~150 m).
Resolution
H3 resolution. 9 (~175 m hex) is the one every layer holds; 10 (~65 m hex) is roughly 7×
the cells for the same area. Which resolutions a layer supports varies — GET /v1/h3 lists
them per layer. The geohash grid's equivalent is precision.
Confidence label
A per-POI field (confidence_label) summarising the structural evidence for a place:
register_verified (authoritative register, transport network, or authoritative category),
cross_validated (two or more independent datasets agree), or unverified (one dataset,
or echo-only corroboration). Prefer it over the legacy confidence float, which is a
match-quality heuristic and not monotonic against whether a place is real. See
The confidence label.
Source count
The number (1, 2, or 3) of POI sources that contributed to a single consolidated POI.
source_count is the raw dataset count; independent_source_count discounts Overture
rows that are themselves Foursquare/OSM-derived and is the canonical confidence signal.
See How POIs are built.
Station vs stop
A stop is a single physical boarding location (a bus stop, a platform). A station is a logical grouping of stops the public thinks of as one place. See Public transport.
TravelTime
The umbrella brand. TravelTime ships several API products on a single account. Two of them frame these docs:
- Data API — this product. The geospatial data layer documented here.
- TravelTime Routing API — the sibling product. Routes, time-maps, and the h3-fast endpoint that produces the cells you hand to the Data API. You hold the Routing API credentials yourself; Data API never proxies the Routing call.
TravelTime's national transport-graph data is also the source behind the Data API PT endpoints — it's already inside the per-country dataset; you don't interact with it directly there.
See Public transport for the transport-graph side.
Trip
One timetabled journey along a transport line. A line that runs every 4 minutes for three hours has roughly 45 trips in that window. See Public transport.
/v1
The current API version prefix. Treated as a stable contract — anything documented under
/v1 is committed; breaking changes go to /v2.
Weekday morning
The arrival-time window we use for transport frequency rollups. Roughly the busiest commute hour. The underlying provider doesn't currently support off-peak or rush-hour variants. See Public transport.