Blog post

New imperviousness map for Sweden – now you can assess imperviousness with one click

Sep 21, 2022

by Helena Åström, helena@scalgo.com

Today we release a completely new imperviousness map of Sweden. The map is produced using Machine Learning, making it possible to identify land cover with high accuracy from aerial images. The map is developed especially for surface water planning, where evaluations of impervious areas and the effect of changes in imperviousness are important considerations.

SCALGO started developing a new method for efficiently producing land cover maps back in 2019. The first imperviousness map of Denmark was released in 2020 in 20 cm resolution.

Since then, we have been working hard to improve the Machine Learning method further to make even more accurate maps and to make the method scalable to other countries.

And today we are proud to announce that the first high resolution imperviousness map of Sweden has been released to all SCALGO Live users.

Machine Learning – the way forward for detailed land cover mapping

The machine learning method was initially developed together with Aarhus University with input from Danish water utilities and consultants.

We started off with training the model based on data from Danish utilities and consultancies”, explains Jonas Tranberg, Machine Learning specialist at SCALGO. “Initially we identified land cover types based on both orthophotos and LIDAR data, but since the start of the development, we have managed to create a method that only uses aerial images.”

And this has some advantages. Aerial images are updated more frequently than LIDAR data. For example, in Sweden most urban areas are photographed every 2-4 years, whereas LIDAR data is collected irregularly, with some areas relying on data from 2010-2011. This means that LIDAR data cannot follow the fast development especially in urban areas.

If we use aerial images, we can make sure that land cover data is as up-to-date as possible, so this is definitely the way forward”, says Jonas.

A better basis for blue-green urban development

The new imperviousness map for Sweden has a 25 cm resolution and divides the country into 4 categories:

  • buildings
  • other impervious areas
  • pervious areas
  • water

This new map will be useful for everyone working with water and especially in urban development projects”, says Hampus Åkerblom, Market Manager for Sweden. “Impervious surfaces increase fast runoff and flooding in cities, so it is important to understand the impacts of hard surfaces when we, for example, design local retention solutions.”

The imperviousness map is now an integrated part of SCALGO Live. For example, the Watershed tool describes imperviousness with just one click. And don't forget to check out the new Length/Area histogram describing imperviousness along flow paths!

Figure 1. The new imperviousness map is integrated with the Watershed tool

The map is also integrated with the Infiltration and Land use tools released in June last year.

I’m really happy that we finally have a high-resolution imperviousness map in Sweden”, Hampus continues proudly, ”Previously we had to rely solely on the land cover map by Naturvårdsverket which is in 10 m resolution, so this new map will definitely contribute to more precise assessments."

How to work with the new imperviousness map

Here’s some inspiration on how you can start using the map in your work.

1) Describe existing conditions

The new map serves as a good starting point when evaluating imperviousness of existing areas.

There can be situations where an area has changed since aerial images where last taken. In such cases you can use land cover editing tools to quickly update an area and to get a precise description of existing land cover.

Figure 2. Quickly update the imperviousness map in areas where land cover has changed.

2) Create new urban areas

Do you work with urban development? Now you can quickly create a new imperviousness map of your project area to describe how imperviousness is expected to change.

Figure 3. Use the land cover editing tools to make changes in the new imperviousness map - you can build entire new urban areas.

3) Download data

Do you want to use the new imperviousness in other GIS analyses or in hydrodynamic models? Just download the data and integrate it with your other models.

Get started. It’s easy.

The new map is now available for everyone using SCALGO Live in Sweden.

If you have any questions related to the data or don’t have SCALGO Live yet, contact Hampus Åkerblom at hampus@scalgo.com.