.GEOJSON

Introduction

GeoJSON is a way of writing map data in JSON: points, lines and areas, each with a set of properties such as a name or a population. It was written by a group of developers in 2008 and standardised as RFC 7946 in 2016. Web maps use it widely, because JavaScript can read it directly.

Software

• QGIS (Windows, macOS, Linux)
• geojson.io, a web editor that draws the file on a map
• ArcGIS Pro (Windows)
• GDAL and its ogr2ogr converter (Windows, macOS, Linux)
• Leaflet, a JavaScript library that shows GeoJSON on web maps

Structure

A GeoJSON file is one JSON object whose type says what it is. Most files are a FeatureCollection holding an array of Feature objects. Each feature has a geometry and a properties object of any values.

A geometry is one of seven types: Point, MultiPoint, LineString, MultiLineString, Polygon, MultiPolygon or GeometryCollection. Its coordinates are arrays of positions, and each position is longitude first, then latitude, then an optional height, in the WGS 84 system used by GPS. A polygon is a list of rings: the outer edge first, then any holes.