TopoJSON (Topology-Aware JSON)
Open BetaTopoJSON हा GeoJSON चा टोपोलॉजी-जागरूक विस्तार आहे. सामायिक-चाप एन्कोडिंग (बहुभुजांमधील सीमा फक्त एकदाच साठवल्या जातात) आणि निर्देशांकांचे पूर्णांक क्वांटायझेशन वापरते — परिणामी फाईल समतुल्य GeoJSON पेक्षा 60-80% लहान असते. D3.js, Mapshaper आणि Observable साठी प्रमाणित इनपुट; परस्परसंवादी कोरोप्लेथ नकाशे आणि वेब अॅटलाससाठी आदर्श.
मुख्य वैशिष्ट्ये
TopoJSON स्वरूपाबद्दल
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.
TopoJSON फाइल्स कोणता कार्यक्रम उघडतो
खालील कार्यक्रम आणि अनुप्रयोग OSM2CDR मधून निर्यात केलेल्या TopoJSON (Topology-Aware JSON) (.topojson) फाइल्स उघडू, संपादित करू आणि त्यांवर काम करू शकतात:
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.
TopoJSON नकाशे कोण वापरतो
TopoJSON कसे निर्यात करावे
निर्यातीनंतर कसे उघडावे
- 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.
TopoJSON मधील लोकप्रिय नकाशे
TopoJSON (Topology-Aware JSON) नकाशा निर्यात मिळवा
OpenStreetMap मधून व्यावसायिक TopoJSON नकाशे डाउनलोड करा. तत्काळ निर्मिती, कोणतेही क्षेत्र.