2.4. Development history

2.4.1. Version 1 - 2003 - 2007

The development of the 3D City Database was always closely related to the development of the CityGML standard [KoGr2003]. It was started back in 2003 by Dr. Kolbe and Prof. Plümer at the Institute for Cartography and Geoinformation at University of Bonn. In the period from November 2003 to December 2005 the official virtual 3D city model of Berlin, commissioned by The Berlin Senate and Berlin Partner GmbH, was developed within a pilot project funded by the European Union [PGKS2005]. Since then, the model has been playing a central role in the three-dimensional spatial data infrastructure of Berlin and opened up a multitude of applications for the public and private sector alike. As an example the virtual city model is successfully used for presentation of the business location, its urban development combined with application related information to politicians, investors, and the public in order to support civic participation, provide access to decision-making content, assist in policy-formulation, and control implementation processes [DKLS2006]. 3DCityDB was key in demonstrating the real world usage of CityGML to the Open Geospatial Consortium on the one hand, and the practical usability and versatility of CityGML to the city of Berlin on the other hand. This first develop­ment phase was carried out by University of Bonn in collaboration with the company lat/lon GmbH. Oracle Spatial was the only supported SDBMS in that phase and the next (3DCityDB Versions 0.2 up to 1.3).

2.4.2. Version 2 - 2006 - 2014

Within the framework Europäische Fonds für regionale Entwicklung (EFRE II) the project Geodatenmanagement in der Berliner Verwaltung – Amtliches 3D-Stadtmodell für Berlin allowed for upgrading the official 3D city model based on the former CityGML specification draft 0.4.0 in the year 2007. The developments were carried out by the Institute for Geodesy und Geoinformation Science (IGG) of the Berlin University of Technology (where Kolbe became full professor for Geoinformation Science in 2006) on behalf of the Berliner Senatsverwaltung für Wirtschaft, Arbeit und Frauen and the Berlin Partner GmbH (former Wirtschaftsförderung Berlin International). The relational database model (3DCityDB versions 1.4 up to 1.8) was implemented and evaluated in cooperation with 3DGeo GmbH (later bought by Autodesk GmbH) in Potsdam. A special database interface for LandXPlorer was provided by 3DGeo / Autodesk. Later on, a first version of the Java based CityGML Importer/Exporter was developed [SNKK2009].

In August 2008, CityGML 1.0.0 became an adopted standard of the Open Geospatial Consortium (OGC). In the follow-up project Digitaler Gestaltplan Potsdam starting in 2010 the 3DCityDB version 2 (cf. [KKNS2009] and [NaSt2008]) was developed which brought support for all CityGML 1.0.0 feature types. The KML/COLLADA exporter was added as well as a ‘Matching’ plugin. This project was carried out by IGG of TU Berlin on behalf of and in collaboration with the company virtualcitySYSTEMS (VCS) in Berlin. In 2012 the developer team at TU Berlin received the Oracle Spatial Excellence Award for Education and Research from Oracle USA for our work on 3DCityDB. Also in 2012 3DCityDB was ported to PostgreSQL/PostGIS by Felix Kunde, a master student from the University of Potsdam, who did his master thesis in collaboration with IGG [Kund2013].

In August 2012, CityGML 2.0.0 became an adopted standard of the Open Geospatial Consor­tium (OGC). In September 2012, Prof. Kolbe moved from IGG, TU Berlin to the Chair of Geoinformatics at Technische Universität München (TUM). The companies virtualcity­SYSTEMS GmbH in Berlin and M.O.S.S. Computer Grafik Systeme GmbH in Taufkirchen (near Munich) have also been using the 3D City Database in their commercial projects for a number of years. In this context, the Chair of Geoinformatics at TUM and the companies virtualcitySYSTEMS and M.O.S.S. signed an official collaboration agreement on the joint further development of 3DCityDB and its tools.

2.4.3. Version 3 - 2013 - 2018

The work on the new major release version 3.0.0 began in 2013 when Dr. Nagel finished his PhD and joined the company VCS. In Version 3.3.0 the new 3D web client was being added. The webclient was developed by Zhihang Yao with contributions from Kanishk Chaturvedi and Son Nguyen. In 2015 Zhihang Yao and Kanishk Chaturvedi were awarded the first price in the ‘Best Students Contribution’ of the ‘Web3D city modeling competition’ under the annual ACM SIGGRAPH Web3D Conference for the 3DCityDB-Web-Map-Client.

2.4.4. Version 4 - since 2015

The work on version 4.0.0 – especially the support of CityGML ADEs – began in 2015 in the course of the PhD work of Zhihang Yao. One part of his PhD thesis is focusing on the model transformation of CityGML ADEs onto spatial relational databases using pattern matching and graph transformation rules. Support of CityGML ADEs in the Importer/Exporter required a substantial rewriting of the citygml4j Java library, the Importer/Exporter and WFS source code performed by Dr. Nagel starting from 2016. Felix Kunde worked, among others, on performance improvements and restructuring of the PL/(pg)SQL scripts. Son Nguyen added support for mobile devices in the 3DCityDB-Web-Map-Client in 2017. Docker support was added by Bruno Willenborg in 2018. Starting from 2017 all partners worked on updating diverse functionalities, scripts, documentation, and on testing.

2.4.5. Acknowledgements

The 3D City Database project team is grateful and appreciative for the financial assistance and support we received from partners that contributed to the development of version 4.0 and the work on the ADE support.

Government Technology Agency of Singapore

The Government Technology Agency of Singapore (GovTech Singapore) has been developing a 3D city standard for Singapore based on CityGML, to establish a common 3D representation of the city-state. GovTech wanted to extend the representation to include other city features through the ADE approach, and had worked with virtualcitySYSTEMS GmbH to start the development of the ADE support on 3DCityDB. The intent is to open source the 3DCityDB ADE support to the international community, so as to encourage wider adoption and implementation of the CityGML standard and ADEs.

CADFEM International GmbH

Founded in 1985, CADFEM is one of the pioneers of numerical simulation based on the Finite Element Method and one of the largest European suppliers of Computer-Aided Engineering. Through the Leonard Obermeyer Center of the Technical University Munich, CADFEM supports the research on digital methods for the design, creation and maintenance of the built environment and the work on the 3D City Database. Bridging the gap between simulation systems and 3D GIS / BIM is a key requirement for enabling multi-physics Urban Simulations and for building Digital Twins of the urban space. The CityGML ADE mechanism supports this in two ways: 1) city features can be enriched with data that is relevant for simulations, and 2) simulation results can be brought back into the city model, turning it into a dynamic knowledge base. CADFEM is supporting the 3D City Database project to leverage the adoption and usage of CityGML ADEs in the field of Urban Simulations.

Climate-KIC of the EIT

Climate-KIC is a so-called ‘Knowledge and Innovation Community’ about Climate Change and Mitigation. It is one of three Knowledge and Innovation Communities (KICs) created in 2010 by the European Institute of Innovation and Technology (EIT). The EIT is an EU body whose mission is to create sustainable growth. Most 3DCityDB developments at TU Munich were done in the context of the projects Energy Atlas Berlin, Modeling City Systems (MCS), Smart Sustainable Districts (SSD), and Smart District Data Infrastructure (SDDI), all financially supported by Climate-KIC.

2.4.6. List of changes between software versions Notable changes between 4.0 and 3.3

New features and functionalities:

  • Importer/Exporter 4.2: Reworked Plugin API to support non-GUI plugins.
  • Importer/Exporter 4.2: Property projections can now also be defined for abstract feature types.
  • Importer/Exporter 4.1: Added support for using SQL and XML queries for CityGML exports to be able express more flexible and complex filter conditions
  • Importer/Exporter 4.1: Added support for importing CityGML data from (G)ZIP files and exporting CityGML content to (G)ZIP files
  • Importer/Exporter 4.1: OSM Nominatim is now used as default geocoder for the map window. Google Map API services can still be used for the map window and for KML/COLLADA exports but require an API key.
  • Management and storage of arbitrary CityGML ADEs with the 3DCityDB, the Importer/Exporter ADE Manager Plugin and the 3DCityDB WFS
  • New 3DCityDB Docker images to support continuous integration workflows
  • New metadata tables ADE, SCHEMA, SCHEMA_REFERENCING and SCHEMA_TO_OBJECTCLASS for registering CityGML ADEs
  • New prefilled metadata table AGGREGATION_INFO that supports the automatic generation of DELETE and ENVELOPE scripts
  • New function to create entries in USER_SDO_GEOM_METADATA view (Oracle)
  • Function objectclass_id_to_table_name now has a counterpart: table_name_to_objectclass_ids returning an array of objectclass ids (CITYDB_OBJCLASS package in Oracle, part of a data schema in PostgreSQL)
  • New database procedures to enable/disable foreign key constraints to speed up bulk write operations (CITYDB_CONSTRAINT package in Oracle, part of the citydb_pkg schema in PostgreSQL)
  • New SQL script to create additional data schemas in one database (PostgreSQL)
  • New shell and SQL scripts to grant read-only or full read-write access to another schema.
  • Importer/Exporter can connect to different database schemas with the same user
  • Enabling XSL transformations on CityGML imports and exports as well as WFS responses
  • New database operation panel to change the spatial reference system used in the database (incl. optional coordinate transformation)
  • New LoD filter for CityGML exports
  • 3DCityDB WFS allows for exporting into the CityJSON format

Improved and updated features and functionalities:

  • Moved interactive prompts from SQL to batch/shell scripts for better setup automation
  • Added OBJECTCLASS_ID column to all feature tables to distinguish objects from CityGML ADEs. Also extended OBJECTCLASS table by more feature-specific details and inserted new entries for feature properties such as geometry, generic attributes etc.
  • Improved performance on stored procedures by reducing amount of dynamic SQL. Therefore, schema_name parameter has been removed from DELETE and ENVELOPE scripts. Under PostgreSQL these scripts (as well as the INDEX_TABLE) are now part of a data schema such as citydb.
  • DELETE and ENVELOPE are now generated automatically in order to deal with schema changes introduced by ADEs. Therefore, the function prefix has been shortened to del_ and env_ not hit the character limit under Oracle,
  • The CITYDB_DELETE_BY_LINEAGE package has been removed. The only function left is del_cityobjects_by_lineage which is now part of the DELETE package
  • Database migration scripts for version 2.1.0 or version 3.3.0 to version 4.0.0
  • Switching from Ant to Gradle as the new build system for the Importer/Exporter tools
  • Allow import of CityGML files with flat hierarchies between city objects
  • Added support for importing gml:MultiGeometry objects containing only polygons
  • Added support for exporting to glTF v2.0
  • 3DCityDB WFS now supports CORS and provides a KVP over HTTP GET endpoint for every operation simplifying the integration with GIS and ETL software such as FME