GML (Geography Markup Language)

It is an XML-based language defined by the Open Geospatial Consortium (OGC) to explain geographical features. GML has the ability to integrate not only vector data, but all geographic data. 

GML models contain many basic elements; 

  • Property 
  • Geometry 
  • Coordinate reference system 
  • Topology 
  • Time 
  • Dynamic feature 
  • Coverage (including geographic images) 
  • Measurement unit 
  • Instructions 
  • Observations 
  • Map presentation style rules 

There are also many open source GML implementation schemes; 

  • CityGML 
  • AIXM 
  • GeoSciML

CityGML (City Geography Markup Language)

Nowadays, 3D city models are becoming increasingly popular. In 3D virtual cities, urban furniture, trees-plants, traffic lights-signs, people-animals and vehicles are displayed as 3D models. In this way, all spatial data about the city can be collected. 

In order to collect and store spatial information in the city in an XML-based format, an open data format called CityGML has been developed. With CityGML, data including geometric, topological and semantic information of objects can be visualized, as well as querying and analyzing data. Thanks to semantic information, not only location information of objects but also attribute or thematic information can be obtained. 

Together with CityGML; 


  • 3D Urban Models 
  • Smart City Applications 
  • City and Land Planning 
  • 3D Cadastre Applications 
  • Urban Architecture Design Studies 
  • Real estate valuation 
  • Urban Landscape Studies 
  • Tourist Practices and Urban Activities 
  • Environmental Simulation Applications 
  • Disaster Management and Planning 
  • Pedestrian and Vehicle Navigation 
  • Training Simulations 

can be done. 

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