TopoJSON (Topology-Aware JSON)
Open BetaTopoJSON is een topologiebewuste uitbreiding van GeoJSON. Het gebruikt gedeelde-boog-codering (grenzen tussen polygonen worden slechts één keer opgeslagen) en geheeltallige kwantisering van coördinaten — het resulterende bestand is 60-80% kleiner dan een gelijkwaardige GeoJSON. Standaardinvoer voor D3.js, Mapshaper en Observable; ideaal voor interactieve choropletenkaarten en webatlassen.
Belangrijkste functies
Over het TopoJSON-formaat
TopoJSON was invented by Mike Bostock, the author of D3.js, to solve a simple problem: in GeoJSON neighboring polygons store their shared border twice. TopoJSON moves all the lines into a common array of arcs that the objects then refer to. On top of that, coordinates are rounded to an integer grid and written as increments — the file gets sharply lighter.
The format is taken for web graphics and analytics: choropleths in D3, interactive atlases, boundary maps in Observable, lightweight layers for offline applications. The second motive is simplification: during generalization the shared borders move together, and no gaps appear between neighboring districts.
The output is a single document: every layer becomes a separate object inside it — roads, buildings, water and so on — and object attributes are preserved. Coordinates are in WGS84, up to 100,000 objects per layer. The topology is built by our own code, with no external dependencies.
The price of compactness is the rounding of coordinates. The grid step depends on the size of the area: for a district it is on the order of a meter, for a country hundreds of meters. For a web map that is invisible; for precise measurements take GeoJSON or GeoPackage.
Welk programma opent TopoJSON-bestanden
De volgende programma's en toepassingen kunnen TopoJSON (Topology-Aware JSON)-bestanden (.topojson) die uit OSM2CDR zijn geëxporteerd openen, bewerken en verwerken:
Format specifications
- Open standard
- 2D only
- Lossless (no quality loss)
- Stores feature attributes
- Output: 1 file
- TopoJSON (open spec). Topologically encoded GeoJSON: shared borders stored once, file size 30-80% smaller. Used by D3.js.
Wie gebruikt TopoJSON-kaarten
TopoJSON exporteren
Openen na de export
- D3.js — include topojson-client and unpack the layer you need: topojson.feature(topology, topology.objects.buildings), then the usual d3.geoPath.
- Mapshaper — drag the file onto mapshaper.org: objects and attributes are visible, and simplification and export to SHP or GeoJSON are right there.
- QGIS — opens .topojson as an ordinary vector layer through GDAL; handy for checking the geometry with your own eyes.
- Converting to GeoJSON — topo2geo buildings=buildings.geojson < map.topojson from the topojson-client package, or ogr2ogr.
- Leaflet and MapLibre — they do not understand the format directly: unpack it into GeoJSON on the client with the topojson-client library and feed it on as usual.
Populaire kaarten in TopoJSON
Ontvang TopoJSON (Topology-Aware JSON)-kaartexports
Download professionele TopoJSON-kaarten van OpenStreetMap. Directe generatie, elk gebied.