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3D city modelling for effective governance

Dr. Florian Siegert
Managing Director & CEO, 3D RealityMaps GmbH
[email protected]

Real estate marketing, location study, solar cadastre and city planning – these days detailed photorealistic three-dimensional city models offer the basis for a multitude of applications and services for many local authorities. A central and very interesting way of usage is emerging with the promotion of towns or cities for tourists, companies and also investors. Creative and innovative ideas are required to successfully compete on the national and international market.

In the case of tourism, cities can, for example, gain an advantage by informing their potential visitors before beginning their journey. More and more cities therefore, invite to a virtual city tour on the Internet showing their highlights in a 3D city model.

However, considerable financial and human resources are necessary for creating a 3D city model.

Many metropolises have already made this effort and have a digital model of their city. But to also enable smaller town councils in having their own 3D model IT-specialists of the company 3D RealityMaps have, besides the creation of high resolution 3D landscape models, also refined and revolutionised the technology for 3D city modelling. For the first time, photorealistic city models can be created with a single-shot photo flight through a new and completely automatic procedure. 3D RealityMaps promises, that this already reduces costs in the first project phase.

First, a high resolution digital elevation model is derived from the aerial images through a technique called “dense matching”. Therefore, aerial images with a resolution of at least 15 cm and which overlaps by 80 percent along-track and 70 percent across-track are required. Alternatively, an elevation model derived from a LiDAR flight can be used as a basis for the automatic reconstruction of the building geometries. In the next step, a true orthomosaic is created which serves as a ground texture.

With intelligent algorithms, like the analysis of topological relations, triangulation and simplification without losing shape information, an abstracted city model finally comes into being. Like this, entire cities are reconstructed in highest detail in short time. (Figure 1).

Figure 1: A photorealistic 3D city model from Munich fully automatically created from a single-shot photo flight.

The advantage of this automatic building extraction lies especially in the reduction of manual interactions and thereby, makes the production of large-scale city models more budget-friendly. The so created city model is not detailed down to each building. Therefore, the 3D city model is merged with building outlines from the cadastre. Through this the city model can be enriched semantically with technical data.

From the aerial images, 3D RealityMaps extracts views of the building facades. These are also integrated into the model. The result is a high resolution and photorealistic 3D city model which can be exported into the common CityGML format and can be interactively visualised with Google Earth or with the 3D RealityMaps software. For special buildings, like churches and museums, 3D RealityMaps creates CAD models and integrates them into the model.

Figure 2: A photorealistic 3D city model of Kassel town

The completed 3D city model can be enriched with a multitude of useful geodata which is displayed in its spatial context. Tourists thereby, receive extensive information about the town, hotels and sightseeing attractions. The town’s residents again can obtain information about building plans, real estates, public institutions and local passenger traffic.

Not only in combination with city marketing or tourism but also for city and infrastructure planning, real estate marketing or the promotion of economic development, cheap photorealistic 3D city models offer new possibilities.

With a digital representation a local community, for example, can present itself as a new site for a company. New buildings can be simulated or areas for industrial use can be declared. For the suitable visualisation the company has self-developed software in its portfolio. This software based on a hierarchical LOD technology contains tools for 3D processing of the data as well as for the visualisation on the Internet. Additionally, the company on demand offers the user an interface to integrate their own GIS data as well as various analysis tools for city administrations.

Currently, 3D RealityMaps is adapting its 3D streaming software for mobile devices. Photorealistic 3D landscapes can already now be accessed online and offline on smartphones and be used for route planning and navigation (Figure 3). The first App supporting mountaineers in summiting the Zugspitze, the highest mountain in Germany, will be available this summer for Android and iOS. Through this the company aims to make orientation in cites or in outdoor areas as efficient and as safe as possible.

Figure 3: Photorealistic 3D landscape visualisation on a Samsung S3 Smartphone.