L'Antarctique sort à peine de sa torpeur hivernale que déjà deux évènements majeurs viennent de se produire sous l’œil de Sentinel-1.
Le 12 juillet dernier, une crevasse géante à fendu la barrière de glace Larsen C , mais il a fallu attendre que la banquise desserre son étau en septembre pour que l'iceberg A68 commence à dériver. Ce glaçon couvre une superficie de 5800 km² (les deux tiers de la Corse).
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).
Le Monde.fr a publié un reportage frappant "Au Brésil, avec les policiers qui luttent contre la déforestation de l’Amazonie". Le journaliste et photographe Bruno Kelly a suivi les agents de l’institut pour l’environnement et les ressources naturelles renouvelables (Ibama) dans les environs d'Apui, une petite localité isolée au sud de l'état d'Amazonas. Il écrit que "le chef de la police reconnaît que contrôler avec 1 300 agents une zone de la taille de l’Europe occidentale est une tâche pour le moins difficile".
The animation below shows the evolution of Thwaites glacier eastern ice shelf in West Antarctica, from July 2016 to May 2017. I made it with 45 quicklooks of Sentinel-1 radar images processed by the Alaska Satellite Facility and available via the vertex data portal. All images were acquired in interferometric wide swath mode (polarization HH, only ascending passes, path: 65, frame: 914) and projected to ground range.
As you probably know, PEPS is the French Collaborative ground segment for Copernicus Sentinel program. And, first of all, it is a mirror site that distributes all the Sentinel data in near real time. These last weeks, real time was not available for Sentinel-2, as the data format and structure of Sentinel-2 products had deeply changed, and the software needed adaptation. PEPS team created a new collection, named "Sentinel-2 Single Tiles", coded "S2ST" to separate the old format from the new one. Now that the new version has been installed and validated, the PEPS mirror site is once again up to date.
The giant ice avalanche that occurred in Tibet on 17 July 2016 and killed 9 people  urged scientists to scrutinize every available data to understand what caused such a glacier collapse. In doing so, they witnessed in near real time the ongoing collapse of a second glacier.
Short after working with Simon on the script for the article about the mapping of flooded areas, I wanted to be sure that our short script was realistic. I had some time to loose at the airport, so, after finding a wifi connection, I looked for pictures of the flooded areas of the north of France. I found some impressive pictures of the damages like the hippodrome of Mesnil Le Roy and surrounding places, but the most stunning one was surely this aerial view of Chambord.
Francis the 1st was the king of France during the first part of the XVI century. After winning the battle of Marignano, he decided to build a castle to its own glory. The castle is actually located 5 km south of the Loire river in between the cities of Blois and Orleans. The small Cosson river also crosses the park as can been seen on the aerial view. The Cosson overflowed at the end of May 2016 causing damages to the castle estimated in between 0.5 and 1 million euros.
After doing some slight adjustment to the original script, I exported the result from Earth Engine as a Geotiff file and encapsultated it into a KMZ file to load into Google Earth. Some people had already prepared a 3D model of the castle, so it was quite easy to create this 3D view.
Well, I'm really sorry for King Francis, but it seems our first guess of mapping flooded areas was not bad at all.
Dave Petley wrote a nice article in the AGU's Landslide blog about a massive landslide in Glacier Bay, Alaska. This huge avalanche of debris was spotted by a local pilot Paul Swanstrom on June 28. When Paul was above it, "dust was still flying". Later, based on earthquake records in Alaska, the experts figured out that it probably happened at 8:21 am on the same day.
Photo of the the Glacier Bay landslide in Alaska by Paul Swanstrom - MountainFlyingService (click on the image to see the Facebook photo album)