Mapping of the effects of drought in cities using satellite data

The World from Space start-up provides a bird's-eye view of the world. Every couple of days, it makes accessible and interprets satellite images of the Earth's surface. Government officials as well as citizens can easily find out which areas in their cities are threatened by droughts or what is the current state of urban vegetation and quality of air. Moreover, photos captured from outer space can be put to great use in agriculture and forestry. Roman Bohovic, the founder of this start-up company and graduate of FIT BUT, wants to support protection of the environment by spreading relevant up-to-date information.

Satellite images from the European Copernicus programme, which uses several satellites for monitoring of the Earth's surface, are available to everybody, free of charge and in full resolution. However, the interpretation of the data is a tough nut to crack. "You have to know your way around this type of images and be able to work with them. Correct understanding of the processes occurring on the Earth's surface and the ability to distinguish possible errors from natural phenomena requires knowledge from the areas of informatics, cartography and geography. On top of that, we are working with big data. Literally. We are receiving terabytes of data from the satellites every day which we have to process and analyse," explains Roman Bohovic, the founder of World from Space.

In the start-up company focusing on the interpretation of satellite images, Bohovic makes use of the knowledge he gained throughout his university studies of informatics at the Faculty of Information Technology of BUT and geography at the Faculty of Science at Masaryk University. He co-founded the start-up with his friend, Jan Labohý, when he realised that nobody in the Czech Republic was offering a job position he would really be interested in. "I have always been interested in protection of the environment and I like combining natural sciences with technology. I saw a great opportunity in the use of freely available satellite images. I wondered how to make the data available so that it can be used in practice by both the general public and private enterprises," said the young researcher about the beginnings of World from Space, his company seated in Brno in the South Moravian Innovation Centre.

At first glance, satellite images look a lot like aerial photographs. However, the territory captured in such image is much larger and the data is more up-to-date since the satellites send images approximately every four days. Dispatching aircraft to take picture this often would be too expensive. "Imagine an ordinary photograph of land surface, only these images are not made in three RGB layers, as we know from our computer screens. Instead, these images consist of 13 colour bands, including the infrared band. We then select the specific layers relevant for our monitoring - for example the vegetation, humidity or temperature indexes," Bohovic explains.

These three quantities are the ones that the analysts decided to make available to the public via their web application, which was tailor-made for the city of Pilsen. People can see how much urban greenery there is as well as what are the hottest areas in the city. "Heat maps of the city processed based on our data clearly show that large industrial parks and areas with no green spaces are overheating more than any other areas in the city. The situation is not as critical in streets at least partially lined with trees," said Bohovic noting that the temperature differences measured in one city ranged up to 10 degree Celsius during the summer heat waves. Prague and Brno have started to use the monitoring of their territories based on satellite data as well.

"The climate change is real and we are trying to show both citizens and municipal self-governments that our satellite data can be used to propose effective measures that would help areas threatened by droughts and excessive heat. Temperature is going to rise in the future and we need to start preparing for it right now," warned Bohovic. The start-up company offers to cities not only an analysis of the current situation but also proposals for adequate strategic solutions.

The difference in the city surface humidity between two summer days - the first measured after a heatwave lasting several days, the second after a heavy rainfall | Author: World from Space Archive

The Copernicus satellites provide more than just up-to-date satellite images. They have been gathering data about the Earth's surface for four years and thus enable the analysts to monitor the development of individual territories and perform year-by-year comparisons. "Last year, there has been a lot of press concerning droughts at the end of summer. However, it is often difficult to say precisely how severe a particular dry spell is. We can compare and quantify data on a year-by-year basis for example from the perspective of a farmer or urban architect. We can see that the dry spell occurring at the end of last summer was by far the most severe over the four-year period for which we have our data. We can also see that there is a relatively high number of droughts over different periods of the year. This year, we observed a marked agronomic drought at the beginning of the spring, which most of the people did not notice due to lower temperatures. However, it had strong impacts on agriculture production," explained Bohovic.

Farmers may benefit from satellite data and use it to plan their harvests and crops. The analysts from World from Space offer reference material for "smart farming", which include not only monitoring of the current condition of fields and vegetation, but also analyses of the development of drought combined with current condition of the crops in the fields. Satellite images can also be used in forestry. "We can monitor the scope of dead and withered trees as well as the course of the bark beetle crisis," added Bohovic.

Satellite images are useful for urban architects and city planners in preparation of land-use plans. "If a city plans an investment, it should know the current situation at the given place. However, cities often use older data or only the general data layers. This problem also concerns green spaces. Sometimes, there are simply no trees to see in the streets. However, we can see from the satellite images that there actually is enough urban greenery in the given area - mainly the trees and lawns on private properties and in the inner courtyards. Therefore, the microclimate of the street is quite good despite the fact that the city does not have many trees in the area. In situations like this, it is beneficial to invest and extend green areas in different parts of the city," noted Bohovic.

Currently, the experts from the start-up company are developing an automated web application that would serve in the Czech Republic as a widely available reference material helping people to adapt to the climate change. Even small municipalities, which administer small territories and expert custom-made analyses are too expensive for them, could use it. But the founder, Roman Bohovic, plans to go even further: "In co-operation with FIT BUT, we are preparing a project in which we want to test an AI algorithm for analysis of the satellite data. Thus, the evaluation of such data could be much more effective and more deeply automated. At the same time, since we have been incubated by the European Space Agency, we want to focus on projects extending beyond the borders of the Czech Republic."