Map of Bion in TopoJSON format
A map built from OpenStreetMap data, ready to download
Customize the map
Open this place's area in the constructor and adjust everything to your needs
Open in constructor →Map passport
What this map contains by default
This is how the map is built as-is — every setting can be changed in the constructor.
.topojson
About TopoJSON
Map of Bion in TopoJSON: 1 buildings, 24 km of roads, 4 points of interest, 100% green areas — in the WGS 84 coordinate system, units are meters.
Which layers are in the file
This file for the selected area contains:
- Roads
- Buildings
- Greenery
- Points of interest
Geometry by layer
- Roads — lines (LineString) with OpenStreetMap tags
- Buildings — polygons (Polygon) with OpenStreetMap tags
- Greenery — green-zone polygons with tags
- Points of interest — points (Point) with names and tags
What the file carries
The TopoJSON file for Bion: the whole map comes as a single file, the file is plain text and opens in any editor, layers live inside the file as named entities, OpenStreetMap tags are kept as feature attributes.
File size
The expected size of the TopoJSON file for Bion is about 427 KB; the exact size depends on the chosen layers and area.
Coordinate systems
WGS 84 (EPSG:4326), selectable in the wizard
Units
Meters (projected in the chosen coordinate system)
| Category | GIS |
| File extension | .topojson |
| Tier | Open Beta |
How to use TopoJSON for Bion
- 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.
Programs that open TopoJSON
FAQ: TopoJSON for Bion
How does TopoJSON differ from GeoJSON?
GeoJSON stores each polygon with its own boundaries — neighbours duplicate the shared edge. TopoJSON moves shared edges into a separate arcs array referenced by objects. File size drops 60-80%, and topology survives simplification.
Can I convert TopoJSON back to GeoJSON?
Yes, in one command via topojson-client: topo2geo input.topojson out.geojson. Most GIS apps convert automatically.
Why does D3.js prefer TopoJSON?
D3.js renders thousands of polygons fast — shared edges are drawn once. Topology preservation also lets you simplify the map without creating gaps between regions.
Does TopoJSON support 3D?
No, the spec is limited to 2D coordinates (lon, lat). For 3D, use CityJSON or GeoJSON with altitude.
How are the layers arranged inside the file?
All the layers sit in one document: each becomes a separate object in the objects section — roads, buildings, water and so on. They can be unpacked into GeoJSON one at a time, without touching the rest.
