3D city models and their multiple objectives

3D city models can be used in mapping applications, city planning, virtual events and as a starting point for various other applications. At Aalto University, research on the subject has focused on ways to use city models in the capital region and on the application of new 3D mapping technologies to city modeling.

Large three-dimensional (3D) models of urban environments are already familiar – you can explore one in a video game, for example – but they can also be used for information services, research, and the business activities of communities. cities. 3D modeling of cities has become a common task in producing geographic data for cities. The Built Environment Measurement and Modeling Research Institute (MeMo) at Aalto University in Finland studies city models and produces the data used in their creation.

The MeMo research group produces data for city models through a variety of measurement and 3D modeling methods. In particular, it uses methods based on photogrammetry or laser scanning, in particular aerial imaging by drone, terrestrial laser scanning or mobile mapping based on SLAM, explains Arttu Julin, doctoral student in the group.

Three-dimensional city modeling and open data have both made significant progress in Finland, to the point where researchers can use entire datasets, saving them from starting at the mapping stage.

“The current research focuses instead on increasing the level of detail of 3D city models in areas of interest, for example to support urban development. To get more detail in a smaller area, we can use the laser scanning or drone-based measurements These methods are also a regular part of our research, ”adds postdoctoral researcher Juho-Pekka Virtanen.

Build smart data models

MeMo researchers are currently participating in two projects related to the use of 3D city models in the capital region: Helsingin älykäs tietomalli 2025 (Helsinki Smart Digital Twin 2025) in collaboration with the city of Helsinki, and the KAOS Project (Development of knowledge capital in 3D city modeling) financed by the European Social Fund.

“The Helsinki Smart Digital Twin 2025 project focuses in particular on the use and development of 3D city models of the capital. Its goal is to discover new and more efficient ways of using city models in different processes and business life. The project aims to increase knowledge and develop expertise and the economic base between the city of Helsinki, its citizens and its businesses, ”according to Julin and Virtanen.

As part of the project, mapping campaigns are undertaken for research purposes. Research questions focus on increasing the level of model detail in a given area and integrating building interiors into the 3D city model. As these types of data sets are not directly and freely available, they have to be produced within the scope of the project, for example by SLAM laser scanning. The project is carried out in close collaboration with the 3D team of the city of Helsinki.

The KAOS project aims to increase expertise related to city models in the cities of Espoo and Helsinki and in companies. Instead of research, the project focuses on communications, events and mutual development among stakeholders. Virtanen claims that the areas that still need to be strengthened are the technical basis for city modeling, the use of whole 3D city models that supports whole organization processes, and the use of city models. 3D as shareable data resources.

Models of three-dimensional cities around the world

The Finnish capital region is by no means the only area from which the city model data was collected. In Helsinki and Espoo, city information modeling is based on CityGML, the format established for producing city information models. The creation of similar information models has been prolific especially in Europe, with models created for cities like Rotterdam, Berlin and Vienna; Switzerland even has a national project aiming to model the whole country.

“In addition to the semantic CityGML information models, there are many photorealistic and visually impressive 3D city models, such as the separate 3D mesh model of the city of Helsinki. Realistic city models – detail-oriented and visually appealing appearances – and their production have also been part of our key areas of research here at Aalto. It is evident that the “photorealistic” and “semantic” approaches come close to each other. An example would be the strong tendency to develop and build digital twins of cities based on games. technology, ”notes Arttu Julin.

“The 3D modeling of the city in the capital region is done at the international level. This means that many of the questions we study in our research projects are also interesting and timely abroad. Many European cities are currently grappling with similar issues, ”comments Virtanen.

Giving meaning to urban environments with the help of apps

The research group developed the Palvelututka application (Radar Service, only available in Finnish) as an example available for free, based on service data from Helsinki City APIs and 3D models of the city itself. “The main idea of ​​Palvelututka is to combine open datasets already available in a single browser-based application. Here, the 3D model serves as a platform to present information from different sources, providing a three-dimensional environment for interpret that. information, ”Julin says of the app.

The app can be particularly useful when reconstructing a multi-level urban environment, such as Kalasatama in Helsinki. According to Virtanen, the 3D model offers a much easier and more visual way of presenting information related to an environment, as navigating these types of places is often difficult with two-dimensional maps alone. the Source code of Palvelututka was also made available free of charge.

City model data for research, commerce and more

Data from the city model can also be used in a variety of ways to support research. Julin says that city modeling offers countless approaches for the study of geoinformatics, geography and architecture, among others, as it provides many ways to visualize urban environments and a basis for different analyzes. and simulations.

In addition to presenting information, a city model can also be used for analysis. A city information model that combines other types of information with the physical appearance of places can be particularly useful. useful for computer analysis. In our publication “Near real-time semantic view analysis of 3D city models in a web browser“We present an analysis in which geographic data was added to a city information model in order to assess views in a city – the amount of vegetation or water that can be seen from a window of a city. building, for example. This type of analysis based on a The city model could be used when studying real estate economics or urban experiments, for example. Of course, carrying out such studies would also be research. geoinformatics per se ”, explains Virtanen.

The city models have found commercial users, especially among companies that deal with urban environments. Models of cities can be attractive in many other areas as well, as they offer the ability to present information alongside navigation and provide a starting point for various simulations, which means they can help plan deliveries or events. News agencies, other media companies, and the entertainment and game development industries also used city models. Over the past year, the models have also been a part of various virtual events.

Citizens can also benefit from services built on models of cities. “For example, the Helsinki Energy and Climate Atlas gives anyone the opportunity to experience the solar power generation potential of their home, ”says Virtanen.

The original version of this article was published on the website of Aalto University, Finland.