Sentinel-2 et Landsat-8 font équipe pour suivre la coulée de lave du volcan Kilauea

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Le volcan Kilauea à Hawaï est un des plus actifs au monde. Cela fait déjà plus de trente ans qu'il est entré en éruption, mais il a fait les gros titres récemment car ses coulées ont atteint l'océan Pacifique, agrandissant le territoire hawaïen de deux hectares d'un coup ! Voilà une technique efficace pour lutter contre la hausse du niveau de la mer...

Photo aérienne de la coulée de lave 61G au point d'entrée dans l'océan Pacifique le 19 août 2016. Crédit: U.S. Geological Survey Department of the Interior/USGS U.S. Geological Survey.

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Sentinel-2A and Landsat-8 team up to track Kilauea Volcano's lava flow

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Kilauea Volcano in the largest active volcano in Hawaii and one of the most active on Earth. It has been erupting for over 30 years now but hit the headlines recently because a large lava flow traveled up to the ocean, adding 2 brand new hectares to the Hawaiian Islands.

Aerial view of the 61G lava flow ocean entry on August 19, 2016. Credit: U.S. Geological Survey Department of the Interior/USGS U.S. Geological Survey.

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Sentinel-2A (and Landsat-8) capture a giant ice avalanche in Tibet

After reading my previous post about the Rutog ice avalanche, my distinguished colleagues Antoine R. and Olivier H. challenged me to look for a pre-event image to better highlight the avalanche area. The closest clear-sky image that I could find is a Landsat-8 image that was acquired on June 24 (23 days before the slide).

 

Sequence of two Landsat-8 and Sentinel-2A images. Both images are level 1 product displayed as natural color composites. Click to enlarge.

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Sentinel-2A captures a giant ice avalanche in Tibet

The Nature News website reported yesterday on a massive ice avalanche that happened in Rutog, Tibet, on 17 July 2016. This ice avalanche killed 9 people and may be one the largest ever observed. The ice and rock mixture spread over 6 km from the collapse point up to the Aru Co lake shoreline.

Sentinel-2A image of the Rutog ice avalanche acquired on 21-Jul-2016 (4 days after the event). Click on the image to see at full resolution (1 pixel = 10m).

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Snow and Fire in the Dragon mountains

NASA's blog "Image of the Day" recently featured two beautiful MODIS images of the snow cover in Lesotho. In late July Lesotho experienced its heaviest snowfall in two decades. The snow is not uncommon in Lesotho given that over 80% of the country lies above 1800 m (wikipedia). However the frequency of such snow events has been reducing over the past decades due to the ongoing climate change. As a result the shepherds are less accustomed to the snow conditions so that "a severe storm like the one in July 2016 has greater potential to kill sheep and shepherds" [1]. Continue reading

Mapping the Glacier Bay landslide using Sentinel-1 and Sentinel-2

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)

 

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Mapping flooded areas using Sentinel-1 in Google Earth Engine

Exceptional rainfall in May caused heavy flooding in the Paris region. Newspapers and TVs reported that the Seine flood forced the Louvre staff to move away from rising waters the art pieces that were stored in their cellar. But they did not tell you that about 50 km east of the Louvre museum, the flood of the Grand Morin river in Coulommiers also inundated the cellar of my parents-in-law. I'm really concerned about this cellar because I care about my parents-in-law of course, and also because I have let some of my bottles of wine in their cellar. Continue reading

Sex ratio at LPS16

I did not have the chance to attend the latest ESA's Living Planet Symposium so I was curious to read Olivier's report. The picture in his post shows a crowded room... but what stroke me most is that it looks like 90% of the people in the room are middle-age men. There is no public data on the age or the sex of the participants to the LPS16. But there is a page on the LPS16 website listing all the authors.

A room at LPS16

A room at LPS16

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Série temporelle de chats

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La télédétection satellite optique est un outil formidable pour suivre l'étendue du manteau neigeux en montagne... sauf quand il y a des nuages ! La télédétection radar du manteau neigeux (indifférente aux nuages) n'est pas encore opérationnelle en zone de montagne, notamment en raison du fait que le signal rétro-diffusé par le manteau neigeux varie très fortement avec son contenu en eau liquide. Sur le plancher des vaches, en revanche, de nombreuses personnes observent le manteau neigeux, même sous un ciel couvert. Certains sont même assez gentils pour prendre des photos, les télécharger sur un site web de partage, et les mettre à disposition sous licence publique. Une bonne partie des photos est géolocalisée, soit parce que l'appareil photo est équipé d'une puce GPS, soit parce que le photographe a lui-même ajouté les coordonnées de la prise de vue lors de la publication de son album.
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Kittens time series

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Optical remote sensing is great to map the snow cover extent in mountain regions as long as there is no cloud above the land surface. Radar remote sensing of the snow cover is not operational yet mainly because the backscatter from the snow surface is strongly dependent on the snowpack liquid water content. On the ground, however, thousands of people are observing the snow cover in the mountains, everyday. Some of them take photographs and kindly upload them to photo-sharing websites with a public license. Many of these photos are geotagged, either because the cameras have built-in GPS, or because the users added geographical coordinates when publishing their album.
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