3D city models: "This is a domain I would like to continue to promote and advance in the future"

There is no question that studying at HFT Stuttgart is worthwhile for students. One whose success story took a steep upward curve is Maxim Rossknecht. His master's thesis on the 3D city model in the Finnish capital Helsinki was well received by experts. And so, it's no surprise that he won the student competition of the 3D City Models Working Group for his research at the end of last year. We spoke with Maxim Rossknecht about his master's thesis, the overall view of the energy-efficient building environment, and what other cities and municipalities can learn from Helsinki with regard to 3D city models.

Mr. Rossknecht, at the end of last year you won the student competition of the 3D City Models Working Group for your master's thesis. How does that feel?

Maxim Rossknecht: It's quite an honor to not only be recognized for your work by being graded, but also to be recognized for your work by a committee in exactly this topic area. 

You also presented the topic to about 170 participants at a workshop on 3D city models. What were the reactions of the plenum to your findings? 

Maxim Rossknecht: It was a nice opportunity to present my work to an audience interested in the same topic area. I was contacted after the presentation and invited to an exchange to discuss if and how similar analyses can be transferred to a city in Germany. 

Let's go into a little more detail about your work. What are the key points of the work and, above all, the results? 

Maxim Rossknecht: The city of Helsinki has set itself the goal of being carbon-neutral by 2035. Since heating buildings there causes more than half of the emissions, a lot needs to be done in this domain to achieve the goal. In my work, I used the 3D city model of Helsinki to simulate the heating demand of buildings and calculate the resulting CO2 emissions. Considering various factors such as climate change, CO2-efficient district heating, and energy retrofits, I considered different scenarios of how the heating demand of Helsinki's building stock could change by 2050. What I found most interesting was that climate change would decrease heating demand by 4% per decade, but in turn increase the need for building cooling in the summer. If 1% of the building stock were to be energy retrofitted each year between 2020 and 2035, the resulting CO2 emissions could be reduced by about 10%. In order to achieve the target of an 80% reduction compared to 1990 CO2 emissions, the City of Helsinki has another set screw in addition to energy retrofits. In Helsinki, over 90% of the buildings are connected to the district heating network. In the future, this will use less coal and more renewable energy. Thus, CO2 emissions for heating buildings can also be drastically reduced. In my work, I have also considered this scenario and concluded that with a one percent renovation rate and the more CO2-efficient district heating network, emissions could be reduced by about 79% compared to 1990. If we increase the renovation rate to 3% in this scenario, we are talking about an 82% reduction. Thus, the city's goal could also be achieved. 

With the energy-efficient building environment, you have chosen a topic that must receive increasing attention in cities and municipalities. Unfortunately, there is a lack of an overall view in quite a few cities. With your work here, aren't you also providing some impetus for other cities to do the same in Helsinki? 

Maxim Rossknecht: I hope that I have been able to demonstrate the benefits of 3D city models in this domain with my work and that other cities will also try to use all available resources to get closer to climate neutrality. 

Helsinki is one of the European showcase cities in terms of digital urban development. In your view, what are those responsible in the Finnish capital doing right to apply spatial data in a meaningful and, above all, stronger way in its entirety? 

Maxim Rossknecht: Helsinki makes a lot of spatial data publicly available, which I as a geoinformatics expert often search for in vain. Be it 3D city models and associated building information, terrain models or orthophotos, i.e. aerial photographs. Often, this data is also available in other cities in Germany, but is not freely available to the general public.

And what can local cities learn from this?

Maxim Rossknecht: In principle, such an analysis can also be applied to cities here in Germany. The necessary information certainly exists in many cities, but, as described earlier, it is often not available to the general public. In Germany, this can again vary from state to state. Personally, I see some southern states lagging far behind. 

Science and research are key drivers in transferring theoretical models into practice. People like to talk about transfer here. What does this transfer look like in the specific case of Helsinki? 

Maxim Rossknecht: I didn't reinvent the wheel in my work. I collected available data, processed it, applied simulation algorithms to it, evaluated the results and prepared them in an appealing way for presentation. From my point of view, one of the keys is the presentation of the results. Especially with complex issues, data must be presented in a simple and understandable way, and this is exactly where a 3D city model provides a great basis once again. So, I could use it not only for the analysis, but also for the presentation of the results.
 

Speaking of drivers. In what way did your colleagues at HFT Stuttgart support you in your work?

Maxim Rossknecht: The colleagues at HFT Stuttgart supported me during the work not only with their tools, but also with their know-how. Of course, there were questions and ambiguities that had to be clarified, especially at the beginning of the work. But I could always turn to Prof. Coors and his staff, who were usually there for me within a very short time. This is still true today. The contact after my graduation from HFT Stuttgart is still there and people help each other with problems. 

Finally, a look ahead. You have made the leap from HFT Stuttgart to Fraunhofer IGD as a research assistant. What are your current and upcoming tasks as well as goals? 

Maxim Rossknecht: I have now been at the Fraunhofer Institute for Computer Graphics Research, or IGD for short, in the Department of Geoinformation Management for over a year. Among other things, I continue to work there on and with 3D city models and their visualization. I would like to continue to make this domain known and advance it in the future.