For Bonn's city planning officer Helmut Wiesner, "Bonn in 3D," as the project is called, is a "treasure." "In the future, we will accumulate a huge archive," he says. Around 10,000 aerial photos, taken from all four points of the compass with an airplane, form the basis of the model. The model is calculated using so-called 3D mesh technology, which the city purchases from two external service providers. The decisive factor here is that the photos are not taken vertically from above, but at an angle - so that not only the roofs, but also facades are recognizable.

The accuracy is in the decimeter range, which makes the model interesting for purposes other than purely tourism. Three-dimensional line and area measurements are of interest to roofers and builders, according to Wiesner. The intersection function visualizes a fictitious terrain level, which can be used to simulate floods. Not only photos, but also video flights can be saved. The model is not limited to the city of Bonn: The area of the Siebengebirge has also been incorporated.

If it's up to Jochen Wagner, the head of the responsible Office for Land Management and Geoinformation, this is just the beginning: "The model is the basis for a digital twin of our city." In the future, more and more data will flow in. At bus stops, timetables will be stored, and trees will be assigned the information that the last inspector obtained during his tour. Even cold air movements can be stored. Wiesner also wants to use this to estimate developments. "We could simulate how the greenery will grow and look in 30 years," he says. "For future construction projects like urban densification, we'll look ahead to see what impact buildings will have on their surroundings."

So far, the topic of augmented reality is only an idea which Bonn's Chief Digital Officer Friedrich Fuß is working on. All stored data should be available to every citizen at any time, using a cell phone or special glasses that display the info on the spot. He sees this as an opportunity to „de-emotionalize social discussions, for example about construction projects, and make them easier to understand. We can then vividly show how something will really look later on.“

"For all its benefits, this model is actually a waste product," explains Helmut Wiesner. Since 1997, the Office of Land Management and Geoinformation of the City of Bonn has been taking aerial photographs every three years, usually in cooperation with the Bonn public utility company or the state surveying administration. Until now, however, these have only been used in two-dimensional geo-information systems. In 2019, oblique aerial images were now taken for the first time in addition to the usual vertical aerial images. In the future, the aircraft will launch every two years, with the next photos scheduled for 2022.

The cost of each round of digitization is about 90,000 Euro, according to the city. The city does not want to charge money for the model; the photographs would be available to everyone free of charge. "They can do what they want with it," Wiesner said. When it comes to data protection, he says, the city is on the safe side: recordings do not have to be blacked out, as was once the case with the Google Streetview project, because they are not detailed enough. "People are not recognizable at all."

(Original text: Nicolas Ottersbach; Translation: Mareike Graepel)