CityGML

It defines ways to describe most of the common 3D features and objects found in cities (such as buildings, roads, rivers, bridges, vegetation and city furniture) and the relationships between them.

It also defines different standard levels of detail (LoDs) for the 3D objects, which allows the representation of objects for different applications and purposes, such as simulations, urban data mining, facility management, and thematic inquiries.

CityGML is implemented as a GML application schema for the Geography Markup Language 3 (GML3), the extendible international standard for spatial data exchange issued by the Open Geospatial Consortium (OGC) and the ISO TC211.

In its most common implementation, which is the one generally used to disseminate and exchange data, CityGML datasets consist of a set of XML files and possibly some accompanying image files that are used as textures.

The structure of a CityGML file is a hierarchy that ultimately reaches down to individual objects and their attributes.