I just came back from Valencia, where I attended the fifth edition of the Recent Advances in Quantitative Remote Sensing Symposium. It is one of my favourites, thanks to an amazing team of organizers led by Jose Sobrino. It is a unique symposium, because it has only one session where you can even see opticians listen to radarists, or passive microwaves experts share ideas with active microwave experts ! Every three years, it is a way to gather quickly a good sense of the advances in each domain of remote sensing, over lands mainly. Next RAQRS will happen in 2020 in Valencia, and no doubt I'll be there, and not only for the delicious coffee breaks or for the giant paella.
Of course, my talk, available here or visible below, was about Sentinel-2 L2A products, including cloud detection and atmospheric correction. This time, I focused on product validation and provided a lot of validation results obtained by our little team at CNES and CESBIO, with special thanks to Camille Desjardins (CNES) and Bastien Rouquié (CESBIO) and Magdalena Main-Knorn (DLR). I also provided a comparison of MAJA and Sen2cor for various criteria that all show the benefits of using multi-temporal information, as done in MAJA. Despite all that, and although these results were perfectly known by ESA, ESA decided to stick with Sen2cor in their production, supposed to be global next year. The slides explain how this decision was made.
Anyway, as you probably know, you can access MAJA products from Theia, or you may also download MAJA's executable (if you have a powerful linux computer).
Following Simon's publication on Saint Barthelemy island after Hurricane Irma, one of our twitter friends, @Pierre_Markuse, posted a comparison of the South Western part of Haiti, before and after Mathew huricane ravaged it last year, on the 4th of October 2016. As you can see, the whole lands turn brown just after the hurricane. I am really not an expert, so I just can imagine it is caused by the wind cutting branches and trunks and by water run-off taking the lower vegetation away. I read that 40% or the forest and 20% of the shrub has been erased. Moreover, the wind and water must have left mud and dust on the remaining leaves, contributing to the brown color.
However, what is amazing is that by end of November, vegetation comes back ! My guess is that mud and dust disappear, shrubs and trees start to grow new leaves and the low vegetation grows back But experts are welcome to explain how it happens exactly, there is a comment section !
I have an additional special own interest in displaying this information : it is a hard test for how our multi-temporal methods included in MAJA to detect clouds, shadows and aerosols can manage such a case. Continue reading
Delta of the Ebro observed by Venμs on August 18, 2017 (Copyright CNES 2017)
The Ebro (Iberus in Latin) flows into the Mediterranean in Catalonia after a journey of more than 900 km from its source in Cantabria. The current morphology of the Delta results from the significant increase in sediment inputs caused in the 15th century by the intensive deforestation of the river catchment: the conquest of the Americas required the construction of boats. It was at this time that the land emerged over the sea, making the delta this wide plain of which only 10% of the land culminates at more than 2 meters. The construction since 1930 of 187 upstream dams reduces the sediment flow (from 28 Mt / year to about 0.1 Mt / year), which partly explains the erosion currently observed in some parts of the delta.
80% of the area of the delta is devoted to crops, mostly rice producing one-third of the country's production. The rest, protected by the Natural Park, consists of lagoons, reed and rush beds, brackish marshes and sandbanks.
The Delta de l'Ebre is included in one of the sites that will be observed by Venμs every two days for two and a half years. It is part of ClimaDat, a long-term climate research network. Different issues will be adressed: land use, phenology, greenhouse gas fluxes (CO2, CH4, N2O), vegetation productivity, role of saline inputs.
Complement: the evolution of the Ebro delta from the 4th century:
Yesterday, MUSCATE facility at CNES produced 1141 Sentinel-2 L2A products in a day, while the previous record was 762. A few glitches had reduced the production on the previous days, and yesterday allowed us to catch up the back log. At the same time we have started producing data acquired in 2016 for several zones outside Europe and Africa. The total number of L2A products in MUSCATE now amounts to 33071. Congrats and thanks to the development and exploitation teams !
Hier, le centre de traitement MUSCATE au CNES a traité 1141 produits de niveau 2A de Sentinel-2, alors que le record précédent était 762. Quelques petits soucis avaient retardé la production ces derniers jours, et c'est hier que nous avons rattrapé le retard, et en même temps lancé la production des données acquises en 2016 sur un grand nombre de zones hors Europe et Afrique. Le nombre total de produits de nievau 2A atteint maintenant 33871. Félicitations et un grand merci aux équipes de développement et d'exploitation !
Hurricane Harvey hit Texas on August 25. The first Sentinel-1 image of Houston since landfall was acquired on Aug 29 at 00:26 UTC. I'm writing this post at 21:09 UTC. As reported by the local news website chron.com "The most severe flooding is around the Highway 90 and Eastgate areas". This is also what we can see on the image comparison below: dark areas are flooded areas:
Click on this link to see in full screen. Or check by yourself in the EO Browser.
Below is a zoom between Dayton and Highway 90 (full screen):
Images are orthorectified VV backscatter in dB (-20 dB is black, 0 dB is white). The backscatter intensity received by Sentinel-1 drops over flooded soil because the emitted electromagnetic waves bounces off the water surface and thus do not return to the antenna (as explained in this post).
Back from a long summer break, I needed to find something else to do than just catching up with emails... Luckily, the organizers of the 2017 International Glaciology Society meeting in Boulder tweeted this animation of the Vavilov Glacier (October Revolution Island, Russian Arctic):
Done ! All Sentinel-2 data acquired above Italy, Switzerland and Austrian Alps, and processed at level 2A, are now available on Theia website! The data format is described here. We would be very thankful if users in Italy or Switzerland could help us spread the news among remote sensing users in both countries.
The level 2A product provides surface reflectances with a good cloud and shadows mask. The processing is done at CNES, within MUSCATE facility, using the MAJA software, developed by CNES, CESBIO and DLR. The production started with data acquired in December 2016, and will go on in near real time.
That's bad luck, just before the long week-end of the 15th of August, ESA Sentinel-2 ground segment failed and ceased production. This explains why Theia ground segment is not producing in real time anymore.
Pas de chance, le segment sol de Sentinel-2 À L'ESA est tombé en panne juste avant le week-end du 15 août. Ceci explique pourquoi la production de Theia ne s'effectue plus en temps réel.
As a consequence of a ground segment contingency occurred at Matera station, the publication of Sentinel-2 products in the data hubs is temporarily interrupted as of today 11 August. The anomaly is under investigation and the data dissemination is expected to resume by mid of next week.
It is a well deserved recognition for the land cover product developed at CESBIO : NASA's earth observatory blog dedicated its "image of the day" blog post for the 15th of August to this product.
This work was done in the framework of Theia, using iota2 free software also developed at CESBIO. Thanks to the information conveyed by time series,iota2 is a fully automatic processor.
Jordi Inglada's team first published in 2015 a land cover map based on LANDSAT 8 data acquired in 2014, with a 30m resolution.This production was followed, in 2017 by a new map, based on Sentinel-2 data, acquired in 2016, at 10m resolution.
=> Sentinel-2 data acquired above Spain and Netherlands are now available on Theia website! Portugal was already available. We also completed the little part of Belgium that was missing. The level 2A product provides surface reflectances with a good cloud and shadows mask. The processing is done at CNES, within MUSCATE facility, using the MAJA software, developed by CNES, CESBIO and DLR.