Maps and the Internet

National Mapping On Demand

4101.1 - Visualizing City Models in a Web-Browser. CASE: Piloting 3D-Buildings in the Finnish National Topographic Database

Tuesday, July 4
8:30 AM - 8:50 AM
Location: Delaware A

In recent years, the methods for collecting 3D-information have developed immensely. Also new equipment, such as unmanned aerial vehicles (UAVs), have been introduced that can be used for cost-effective point-cloud data capture via laser-scanning. These advancements have led to a better availability of 3D-information and raised an interest in many countries for bringing 3D-buildings into national topographic databases.

In Finland, these issues are relevant in the context of a pilot project that is related to the development of the Finnish national topographic database. Currently, several Finnish municipalities perform their own data capture and use their own data models that are different from the ones used in the national topographic database. Some of the main goals in the pilot project are to create a common data model for buildings, to collect building information from the selected test areas and to visualize this information in 3D-form in a web-browser environment.

Visualization of 3D-Buildings
Three Finnish municipalities: Espoo, Tampere and Kajaani were selected to be the test areas in the project. The 3D-buildings were modeled from these areas in the CityGML format. In Tampere and Kajaani, the data modeling was done from laser-scanned data. In Espoo, the models were created by transforming the municipality’s 3D-vector data into the CityGML format. The created CityGML models were stored into the PostgreSQL / PostGIS database that contained a 3DCityDB database schema. The data import and export processes were carried out with the 3DCityDB Import/Export tool.

The data was exported from the database into the 3D Tiles data structure. The 3D Tiles is an open specification that is optimized for fast streaming and rendering of 3D spatial datasets. The 3D Tiles uses the GL Transmission Format (glTF) and it contains support for Hierarchical Level of Detail (HLOD) where only the visible and the most important tiles are streamed for the 3D scene. Currently the Open Geospatial Consortium (OGC) is considering making the 3D Tiles specification an OGC community standard.

The web-browser visualization was created with a 3DCityDB-Web-Map-Client application that is a visualization front-end for the 3DCityDB. The 3DCityDB-Web-Map-Client is able to utilize the 3D Tiles structures and it uses the Cesium Virtual Globe and WebGL libraries in the visualization. In addition to the 3D Tiles information, we also used the WCSTerrainProvider extension for the Cesium Virtual Globe for bringing a terrain height model from the WCS interface to the application. The WMS interface was used to retrieve ortophotos from the selected municipalities and also to obtain detailed information on the buildings via GetFeatureInfo queries.

Conclusions
The open-source tools for the processing and visualization of 3D data have improved considerably even during the project’s duration. If the OGC decides to standardize the 3D Tiles specification it will certainly increase the interest and activities related to 3D-based visualization of spatial data in web-browsers. It seems to be finally relevant to explore the methods how the national topographic databases can be expanded to contain also 3D-information. This shift into 3D will undoubtedly increase the use of spatial data and bring new business opportunities in the creation of applications related to smart cities.

Pekka Latvala

Research Scientist
Finnish Geospatial Research Institute, National Land Survey of Finland

Pekka Latvala is a Research Scientist working in the reseach group 'Interoperability and geospatial web services' at the department of Geoinformatics and Cartography in the Finnish Geospatial Research Institute, National Land Survey of Finland.
His area of expertise includes spatial data interoperability and harmonization, open geospatial standards and geospatial web services.

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Jaakko Kähkönen

Senior Research Scientist
Finnish Geospatial Research Institute, National Land Survey of Finland

Interoperability and geospatial web services, Open Source
geospatial sofware and Linux administration since 1996.

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Anssi Krooks

National Land Survey of Finland

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Calvin L. Meyer

Cartographer
U.S. Geological Survey

Calvin Meyer joined the U.S. Geological Survey as a cartographer in the National Geospatial Technical Operations Center at Rolla, Missouri in 1984. Calvin has over 32 years of mapping applications experience. He began support of The National Map services in 2009 with cartographic review of base maps. His current role is to provide delivery and service desk support for The National Map users, where he answers questions and resolve problems. He also serves as chairperson of a Cartographic Governance Board, which defines and enforces rules for cartographic representation within The National Map services and US Topo products.

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