How were the 3D models made?

The city information model 

The city information model is based on the city’s map and spatial data, registers, point clouds from laser scanning, aerial photographs and building information models. Although Helsinki’s maps are still partly two-dimensional, they can still be utilised to produce a 3D model of the city.  

The model’s buildings were placed at the right elevation by transferring the buildings’ footprints from the city plan’s base map to the digital terrain model. The buildings were then converted into 3D models by combining the terrain model with a surface model that included the shapes of the buildings’ walls and roofs.

The information model currently includes buildings and the shape of the terrain. Additional objects, such as water bodies, bridges and trees, will be added in the future.

The model is continuously updated.

The reality mesh models

The reality mesh models of Helsinki are based on aerial photographs of the city taken in summer. The model was produced by using an application that converted the photographs into a textured reality mesh. 

The geometry of three-dimensional objects was deduced from the aerial photographs computationally. The accuracy of the model depends on the accuracy of the initial data. Unfortunately reflective, mirrored and moving surfaces are not modelled correctly since these types of surfaces are not accurately depicted in aerial photographs. 

More details on the creation of 3D citymodels can be found in the final report of Kalasatama's Digital Twin project

The 3D history of Helsinki 

The first 3D virtual models of buildings in Helsinki were created back in the 1980s. The impetus for city modelling in Helsinki was the Kamppi-Töölönlahti bay idea competition. The first 3D-modelled buildings were the Sokos-Vaakunahotelli hotel, the main post office, the National Museum and the Central Railway Station.

To support the design work for the Töölönlahti bay and to merge the results of several architecture competitions, the City created a virtual model of the Töölönlahti area in 1999. A year later, the model was presented to the general public as a simulator that enabled free roaming in the City Planning 2000 exhibition. 

Before the turn of the millennium, city modelling was not only time-consuming, but also expensive. The work had to be done manually and the data processing involved was very complex. What’s more, modelling could only be carried out on very expensive, specialised workstations. 

City modelling technologies, namely measuring technology, laser scanning, point cloud processing and oblique aerial photography, as well as computers and the modelling methods themselves, advanced considerably during the first decade of the 21st century. In the 2010s, city modelling has only continued to advance thanks to standardisation, such as data service interfaces and CityGML.

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18.03.2022 07:58