GeoJSON is an open standard format designed for representing simple geographical features, along with their non-spatial attributes. It is based on the JSON format. The features include points (therefore addresses and locations), line strings (therefore streets, highways and boundaries),

polygon In geometry, a polygon () is a plane figure that is described by a finite number of straight line segments connected to form a closed ''polygonal chain'' (or ''polygonal circuit''). The bounded plane region, the bounding circuit, or the two to ...

s (countries, provinces, tracts of land), and multi-part collections of these types. GeoJSON features need not represent entities of the physical world only; mobile routing and navigation apps, for example, might describe their service coverage using GeoJSON. The GeoJSON format differs from other GIS standards in that it was written and is maintained not by a formal standards organization, but by an Internet working group of developers. A notable offspring of GeoJSON is TopoJSON, an extension of GeoJSON that encodes

geospatial topology Geospatial topology is the study and application of qualitative spatial relationships between geographic features, or between representations of such features in geographic information, such as in geographic information systems (GIS). For examp ...

and that typically provides smaller file sizes.

History

The GeoJSON format working group and discussion were begun in March 2007 and the format specification was finalized in June 2008. In April 2015 the

Internet Engineering Task Force The Internet Engineering Task Force (IETF) is a standards organization for the Internet and is responsible for the technical standards that make up the Internet protocol suite (TCP/IP). It has no formal membership roster or requirements and a ...

has founded the ''Geographic JSON working group'' which released GeoJSON as RFC 7946 in August 2016.

Example

Geometries

Points are , yor , y, z They may be ongitude, latitudeor astings, northings Elevation is an optional third number. They are decimal numbers. For example, London (51.5074° North, 0.1278° West) is 0.1278, 51.5074

TopoJSON

TopoJSON is an extension of GeoJSON that encodes

topology In mathematics, topology (from the Greek words , and ) is concerned with the properties of a geometric object that are preserved under continuous deformations, such as stretching, twisting, crumpling, and bending; that is, without closing ...

. Rather than representing geometries discretely, geometries in TopoJSON files are stitched together from shared line segments called ''arcs''. ''Arcs'' are sequences of points, while line strings and polygons are defined as sequences of arcs. Each arc is defined only once, but can be referenced several times by different shapes, thus reducing redundancy and decreasing the file size. In addition, TopoJSON facilitates applications that use topology, such as topology-preserving shape simplification, automatic map coloring, and

cartogram A cartogram (also called a value-area map or an anamorphic map, the latter common among German-speakers) is a thematic map of a set of features (countries, provinces, etc.), in which their geographic size is altered to be directly proportiona ...

s. A reference implementation of the TopoJSON specification is available as a command-line tool to encode TopoJSON from GeoJSON (or ESRI Shapefiles) and a

client side Client-side refers to operations that are performed by the client in a client–server relationship in a computer network. General concepts Typically, a client is a computer application, such as a web browser, that runs on a user's local comput ...

JavaScript library A JavaScript library is a library of pre-written JavaScript code that allows for easier development of JavaScript-based applications, especially for AJAX and other web-centric technologies. Libraries With the expanded demands for JavaScript, an ea ...

to decode TopoJSON back to GeoJSON again. TopoJSON is also supported by the popular OGR tool as of version 1.11 and PostGIS as of version 2.1.0.

TopoJSON Schema

Given a GIS shape near coordinates

latitude In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north pol ...

0° and

longitude Longitude (, ) is a geographic coordinate that specifies the east– west position of a point on the surface of the Earth, or another celestial body. It is an angular measurement, usually expressed in degrees and denoted by the Greek lette ...

0°, a simple but valid and complete topojson file containing all metadata, ''Polygon'', ''LineString'', ''Point'' elements, ''arcs'' and ''properties'' is defined as follows: Topojson shapes-en

References

Sources

* * *

External links

* {{Official website, https://geojson.org
https://geojsonlint.com

topojson/topojson
JSON GIS vector file formats