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Last two decades have proven that remote sensing represents a key tool to improve our knowledge of volcanic systems but also to monitor active volcanoes. Based on the specific case of Piton de la Fournaise, Reunion Island, the most active French volcanoes, we here illustrate how Synthetic Aperture Radar (SAR) data, providing information even in cloudy conditions, make it possible to map eruptive deposits, to quantify their volumes but also to estimate the volcanoes topography (with metric precision) as well as surface deformation fields (with a precision reaching a few millimeters). [ABSTRACT FROM AUTHOR]

Remote sensing is a particularly suitable tool for monitoring land use but also particularly suited for déforestation monito-ring. By launching the Setinel-1 and Sentinel-2 satellites in the Copernicus program, the community now has free data with important time-revisits allowing the greatest number of people to effectively monitor land cover of a study area. This paper présents a land use monitoring method based on the combination of two approaches computed using Open Source tools (QGIS, Orfeo ToolBox, python). First, we focus on land use monitoring at an annual time scale using Sentinel-1 and Sentinel-2 data, and then, by the use f entienl-1 data, we detect changes in the forest cover due to déforestation at bi-monthly time scale. The results obtained show a very good synergy of thèse approaches allowing the complementary of optical and radar data. In order to make accessible the proposed method, ail the used open source tools are available on this link http ://remotesensing4all.net/index.php/2018/09/11/kit-use-des-donnees-radar-sentinel-1-in-de-latelier-radar-du-FOSS4G-en-2018-2/. [ABSTRACT FROM AUTHOR]

This article gives some explanations on the technique of interferometry of radar images: how to use it, which products are obtained and what are the constraints to use it. Since its beginnings in the late 1980s, this method, thanks to the multiplication of acquisitions of radar images, the consideration of different types of pixels and the variable image geometries, knows constant progress to make its use more automatic and more efficient. Here we present some of these advances, which allows us to better identify current and future uses. [ABSTRACT FROM AUTHOR]

Due to the weather conditions, airborne and spaceborne radar imagery is an essential source of information for updating the topographic information in the Amazon. This article presents an overview of mapping initiatives in the Amazon using radar techniques in planimetry as well as in altimetry. Instrumental and algorithmic tendencies are described. The challenges of research on radar mapping methods and their applications are discussed. [ABSTRACT FROM AUTHOR]

This article presents some illustrations of (fully or partial) polarimetric radar data applications for the monitoring of terrestrial surfaces. The first part is dedicated to fully polarimetric radar data. Firstly, a theoretical reminder presents the specificity of fully polarimetric data. Then illustrations are given for vegetation types cartography as well as spatio-temporal processes of sedimentation in a semi-arid area in Tunisia. The second part focuses on partially polarimetric data, of the type acquired by the Sentinel-1A/1B satellite SAR sensors, which will be widely used in future years due to their significant contribution to land surface observations studies for environmental sciences. [ABSTRACT FROM AUTHOR]

Les surfaces en herbe jouent un rôle important tant en terme économique qu'environnemental. Elles regroupent une grande diversité de végétation herbacée (pérenne ou éphémère) et occupent une partie importante de l'espace agricole français (zones de pâtures, prairies, milieux agro-naturels présents entre deux cultures principales). Dans ce contexte, cette étude vise à quantifier l'apport de l'imagerie satellitaire multi-spectrale (optique et radar) pour la mise en évidence des surfaces en herbe.Pour ce faire, des classifications supervisées orientées objet, basées sur un algorithme Random Forest et un zonage majoritaire en post-traitement sont utilisées. Cette étude émane de l'expérience de surveillance des cultures multi-capteurs (MCM'10) menée en 2010 sur une zone de polyculture située dans le sud-ouest de la France, à proximité de Toulouse. L'étude s'appuie sur des images satellites acquises entre le 14 et le 18 avril 2010, avec, en radar, des images en bandes X, C et L (de polarisation HH), en optique, une image Formosat-2, et des données terrain concomitantes acquises le 14 avril 2010. Les résultats montrent que la combinaison des images acquises en bande L (Alos) et en optique (Formosat-2) améliore les performances de la classification (précision globale = 0,85 ; Kappa = 0,81) par rapport à l'utilisation des seuls capteurs radar ou optique. Par ailleurs, la performance F-score obtenue pour les surfaces en herbe varie entre 0,1 pour Formosat-2 ; 0,34 pour la combinaison Formosat-2/ Alos et 0,52 pour Alos. Ainsi, les résultats montrent que la qualité de la classification des surfaces en herbe augmente avec l'augmentation de la longueur d'onde des images utilisées. [ABSTRACT FROM AUTHOR]