The growing fleet of Sentinel satellites continuously scans our planet’s lands, seas and skies to understand their state and changes. Operated by the European Space Agency under Copernicus – the EU’s flagship Earth Observation (EO) programme – these satellites generate over 10 terabytes of valuable data daily. The Copernicus Land Monitoring Service (CLMS) provides, amongst other things, EO-based spatial information on bio-geophysical variables such as vegetation productivity, snow- and land cover and land use characteristics. This gives people the chance to see how characteristics change over time. For all the various applications, a survey by the EU-funded ECoLaSS project revealed that many users have higher demands. They need pan-European monitoring of vegetation phenology, forest carbon stocks, and grassland and arable land use intensity. Such information can help determine the impact of Europe’s contributions to international climate change mitigation policies. “Together with ground-based observations, Sentinel-1 and Sentinel-2 can address such evolving needs, thanks to their frequent coverage of the world. They offer fully free and open data,” says Markus Probeck, coordinator of ECoLaSS. “We can now trace how certain land cover changes over whole seasons, or from year to year. This means we can identify them not only from their colour and texture, but also from their temporal ‘fingerprint’.”
Satellite coverage greatly extended
Before the Sentinels, it was difficult to obtain frequent, cloud-free optical satellite image coverage in high spatial resolution. Limited annual coverage of countries meant that all kinds of land cover and use classifications were based on spectral information in ‘mono-temporal’ imagery, depicting just one state in time. “One of our main innovations was to integrate Sentinel-1 radar and Sentinel-2 optical imagery in an automated way. We also applied Big Data analysis and cloud processing techniques to the complete Sentinel-1/-2 time series,” explains Probeck, Copernicus programme manager at GAF, in Germany. “The additional temporal dimension has enabled greater quality, detail and depth of land cover and use classifications in Europe and worldwide,” he adds. This is crucial for observing vegetation development and management practices, at a high spatial resolution of 10 m.
Tomorrow’s Copernicus Land services
The project consortium’s five EO service companies and scientific institutions analysed six major themes: agriculture; forestry; grassland; impervious areas such as settlements and traffic infrastructure; crop phenology, and the new European land cover classification standard CLC+. Demonstrator products were implemented in eight representative sites across Europe and Africa, each 60 000 to 90 000 km2 in size. Of these, some of these have been recommended as most promising for operational rollout under the CLMS portfolio evolution. Probeck concludes: “ECoLaSS pioneered the systematic investigation, and practical demonstration, of the potential of the vast volumes of Sentinel data with their high spatial, radiometric and temporal resolutions. This will foster new land monitoring applications at continental to global scales at unprecedented temporal frequency, and contribute to a growing ‘Copernicus Economy’.”
ECoLaSS, CLC+, Copernicus Land Monitoring Service, CLMS, crop, demonstrator, Earth Observation, grassland, phenology, Sentinel satellites, time series