L’IGN a mis en ligne un outil formidable pour comparer les photos aériennes des années 1950 avec des prises de vue récentes. Cela permet d’explorer à l’envi l’évolution des paysages, comme par exemple la reforestation des estives dans les Pyrénées (ici le secteur de l’étang de Lers, en 2016 et 1953). Ou bien le retrait […]
Here in southwest France ski lovers did not really enjoy the beginning of the snow season… But how does it compare to the previous years? Using Sentinel-2 and Landsat-8 data, we computed the snow cover duration since September 01 until January 20 for the past three snow seasons in the Alps and Pyrenees.
More exactly: two maps of 934’343’100 pixels! We [1] have processed 6205 Sentinel-2 images and 593 Landsat-8 images to compute the annual snow cover duration in the Alps and the Pyrenees at 20 m resolution for hydrological years 2016-2017 and 2017-2018. The snow cover duration (or snow persistence) is defined as the total number of […]
This is a time-lapse of all clear-sky images captured by Venµs over the Khumbu Icefall near Mount Everest since November 2017 (one year of data, 51 images at 5 m resolution) . Here I used the Level-1C products (i.e. without atmospheric correction) because the Level-2A products are provided at a lower resolution (10 m). Anyway, […]
If you are not afraid to spend too much time while you have urgent things to do, you may have a look to the mosaic of Sentinel-2 monthly syntheses for September over France. You may access to each monthly synthesis using the following links : Or you may also use the viewer below to compare […]
=> We are thinking to distribute a new product that would provide the snow cover duration in the Alps and the Pyrenees over a hydrological year (snow persistence map). Here is a preview of a « beta » version that is only 100 m resolution for now. A few words on the method (see also here): this […]
=> Nous sommes en train de penser à un nouveau produit qui donnerait la durée d’enneigement dans les Alpes et les Pyrénées au cours de la dernière année hydrologique. Voici ci-dessous un aperçu d’une version « beta » (artisanale) qui n’est qu’à 100 m de résolution pour l’instant. Quelques mots sur la méthode (voir aussi ici) : […]
In the Landslide blog Dave Petley has analyzed Planet images of the Pashgor debris flow in Afghanistan (here and here). Here I used two Sentinel-2 images (before and after the event) to show the path of the debris flow from the high mountain area to the Panjshir Valley. Sentinel-2 images have a lower spatial resolution […]
The departmental council of the Alpes de Haute-Provence has put online 6,500 km of hiking trails throughout its territory. These trails are visible on the site www.rando-alpes-haute-provence.fr which works with Geotrek software. To allow hikers to better prepare their outing, it might be useful to add the 20 m resolution snow maps produced by Theia […]