The Netherlands in 3D for sound research

The busy roads and railway lines in the Netherlands cause a lot of noise pollution and it is up to sound experts to examine regularly how big that problem is. This helps them determine which residents in the area are entitled to sound insulation for their homes and how effective a noise barrier truly is. There are also many studies into ways to prevent new noise pollution problems caused by an increase in traffic, along new roads, and at residential construction sites.

Sound experts base their studies on prescribed standard calculations carried out on computers, including special 3D models of the buildings, the soil, and the sound sources, which the experts first have to construct themselves. They look at buildings in Google Street View or estimate the height on the spot and process that information manually. This is very time consuming and as such, very expensive. 

When sound consultant Henk de Kluijver came up with the idea of automatically generating a 3D sound model for the whole of the Netherlands, he called in the help of Tom van Tilburg, researcher and developer at Geodan.

"For this project, we worked closely with other parties”, Henk emphasizes. "Various sound specialists at consultancies, environmental services, and municipalities fed us with ideas and gave us constructive feedback on earlier versions, especially the TU Delft and the Netherlands' Kadaster, Land Registry and Mapping Agency. We are faced by the same challenge and we share the ambition to use big data on a national scale to effectively combat noise pollution. We’re happy to continue doing that.”

"The required basic data were already available," says Tom. "The Basic Registration Large-scale Topography (BGT) is a detailed map of the Netherlands that contains every single curb in the country. Objects such as buildings and roads have also been registered, but there is just one hitch: the BGT is flat, 2D. The third dimension comes from the Dutch Current Height Database (AHN), which contains scans of the entire country that were made from airplanes. The result: billions of data points for all trees and buildings."

"Finally, we use the Basic Registry of Addresses and Buildings (BAG), which contains specific data for every building. Together, these 3 sources form the basis for our 3D model for noise research. So, we start out with a lot of data. The trick is to simplify enough to be able make correct calculations whilst also retaining sufficient detail to do justice to the acoustic reality. We kick out the curbs, but we keep tall sound barriers.”

That balance between simplifying and detail can be seen in the result: 3Ddatalab. It looks like a model, with houses that start looking like building blocks. Sloping roofs are flattened and are given the height of the ridge, as is required for noise studies by law. On the other hand, a complex building is not one big block: garages and extensions, for instance, are included separately. Another important simplification is the automatically generated height lines, which indicate the top and bottom of dikes, hills, and sound barriers and make it easier to include the influence that these elements have on sound transfer in the calculations.

The model keeps getting better. Tom: "We’re looking forward to a new version of the AHN. Unfortunately, it only comes out every 7 years, which means that sound experts still have to check whether new buildings have been added, for example. There are plans to refresh the database every 2 years and to add more details, making our model even more efficient.

Houses in the 3D model look like building blocks and height lines indicate the top and bottom of dikes, hills, and sound barriers.