What is this challenge about?
In this challenge, the participants have to find out how many fields in a certain area have been ploughed - based on the satellite images presented to them. The images come from Sentinel-2 satellites.
To master this challenge, you have to combine different data from the available graphics. This will enable you to interpret the satellite images correctly.
Sentinel-2, consisting of Sentinel-2A and Sentinel-2B, are a pair of optical earth observation satellites and are part of the Copernicus programme, an earth observation initiative of the European Union. Their main task is to take high-resolution images to monitor the environment and document changes on Earth. For example, they are used to analyse climate change or to collect data on natural resources, waters, forests, etc. They are also used to better understand various natural disasters (floods, forest fires).
Do you want to try it too?
This is the map with the fields you want to analyse. Find out how many of the coloured fields have been ploughed.
You can download and print out the map, the satellite images and the graphics here:
Infobox
First of all, the participants must recognise the landscape boundaries on the maps. This is essential in order to interpret the maps correctly and identify the fields.
The next step is to look at the graph of relative reflectance (the other graph with the wavelengths is not really needed for this task). Here you can see how much light (Y-axis) the different land surfaces reflect depending on the bandwidth (X-axis). The higher the line is on the Y-axis, the more light is reflected and the brighter this land surface appears on the image.
In the spectral bands B4 and B11 you can see that soil has the highest reflection rate, i.e. at B4 and B11 ploughed fields will appear brighter than all other surfaces. The ploughed fields are therefore relatively easy to recognise on these images.
Therefore, there are 24 ploughed fields.
Want to know how the contestants from the show mastered this challenge?
Then watch episode no. 5! (will be published on the 2nd of February)
What is the scientific background to this challenge?
Sentinel-2:
The Sentinel-2 satellites are specifically designed to provide high-resolution images of the Earth's surface. They play a key role in areas such as land use and agriculture, environmental monitoring, forest monitoring, climate change and disaster management. Both Sentinel-2 satellites are identical. The data and analysis from Sentinel are freely available to everyone as part of the Copernicus programme.
Why do we use satellite images and not ‘normal’ photos from above?
Satellites use special sensors that are able to measure electromagnetic radiation in different wavelength ranges (spectral ranges) that go beyond the light visible to humans. Humans can only see a small part of the electromagnetic spectrum, namely visible light (approx. 400-700 nm). However, the electromagnetic spectrum is much broader. In the spectral range in which the human eye perceives nothing, all objects nevertheless reflect electromagnetic radiation, i.e. different materials/surfaces appear darker or lighter in different frequency ranges.
The satellite's sensors measure raw data (spectral data), which is stored in a digital format. This raw data is then processed using mathematical models. Sometimes different spectral bands are combined (e.g. Normalised Difference Vegetation Index - NDVI for vegetation) to make certain features or changes in the landscape visible.
This processed data is converted into images that can be interpreted by humans. For example, areas of vegetation can be visualised in shades of green and areas of water in shades of blue, even if this information comes from areas of the spectrum that we cannot see directly.
A few impressions from the fifth episode
Author: Diane Bertel
Editor: Lucie Zeches (FNR)
