CityJSON

CityJSON is a data exchange format for digital 3D models of cities and landscapes. It aims at being easy-to-use (for reading, processing, and creating datasets), and it was designed with programmers in mind, so that tools and APIs supporting it can be quickly built. The JSON-based encoding of CityJSON implements a subset of the OGC CityGML data model (version 3.0) and includes a JSON-specific extension mechanism. Using JSON instead of GML allows us to compress files by a factor 6 and at the same time to simplify greatly the structure of the files.