This repository is where the specifications and the schemas of CityJSON are kept. All previous versions are kept in tags in the commits.
For all the details, see the official CityJSON website: https://cityjson.org.
CityJSON is a JSON-based encoding for a subset of the OGC CityGML data model (version 3.0.0), which is an open standardised data model and exchange format (in GML) to store digital 3D models of cities and landscapes.
The aim of CityJSON is to offer an alternative to the GML encoding of CityGML, which can be verbose and complex (and thus rather frustrating to work with). CityJSON aims at being easy-to-use, both for reading datasets, and for creating them. It was designed with programmers in mind, so that tools and APIs supporting it can be quickly built, and several software have been created already.
We invite anyone to contribute to the development and improvement of CityJSON, all discussions, issues, and developments are open to everyone.
Ledoux H, Arroyo Ohori K, Kumar K, Dukai B, Labetski A, Vitalis S (2019). CityJSON: A compact and easy-to-use encoding of the CityGML data model. Open Geospatial Data, Software and Standards, 4:4 (DOI) (PDF)