Approximate information maximization for bandit games

Entropy maximization and free energy minimization are general physical principles for modeling the dynamics of various physical systems. Notable examples include modeling decision-making within the brain using the free-energy principle, optimizing the accuracy-complexity trade-off when accessing hidden variables with the information bottleneck principle (Tishby et al., 2000), and navigation in random environments using information maximization (Vergassola et al., 2007). Built on this principle, we propose a new class of bandit algorithms that maximize an approximation to the information of a key variable within the system. To this end, we develop an approximated analytical physics-based representation of an entropy to forecast the information gain of each action and greedily choose the one with the largest information gain. This method yields strong performances in classical bandit settings. Motivated by its empirical success, we prove its asymptotic optimality for the two-armed bandit problem with Gaussian rewards. Owing to its ability to encompass the system's properties in a global physical functional, this approach can be efficiently adapted to more complex bandit settings, calling for further investigation of information maximization approaches for multi-armed bandit problems

Spectral coherence applied to vessel tracking

Multi-Chromatic or spectral Analysis (MCA) of SAR images consists in splitting wide band SAR signals into sub-bands to generate several lower resolution images from a single acquisition. This splitting allows performing a spectral analysis of observed scatterers. Spectral coherence is derived by computing the coherence between sub-images issued from a single SAR acquisition. It was shown that in the presence of a random distribution of surface scatterers, spectral coherence is proportional to sub-band intersection of sub-images. This model is fully verified when observing spectral coherence on open seas areas. If the scatterers distribution departs from this distribution, like for manmade structures, spectral coherence may be preserved to a certain degree. We investigated the spectral coherence to perform vessel detection on a sea background by using spotlight images acquired on the Venice Lagoon. Sea background tends to lead to very low spectral coherence while this latter is preserved on the targeted vessels, even for very small ones. A first analysis shows that all vessels observable in intensity images are easily detected in the spectral coherence images which can be used as a complementary information channel to constrain vessel detection.WiMC

Split-Band Interferometric SAR Processing Using TanDEM-X Data

Most recent SAR sensors use wide band signals to achieve metric range resolution. One can also take advantage of wide band to split it into sub-bands and generate several lower-resolution images, centered on slightly different frequencies, from a single acquisition. This process, named Multi Chromatic Analysis (MCA) corresponds to performing a spectral analysis of SAR images. Split-Band SAR interferometry (SBInSAR) is based on spectral analysis performed on each image of an InSAR pair, yielding a stack of sub-band interferograms. Scatterers keeping a coherent behaviour in each subband interferogram show a phase that varies linearly with the carrier frequency, the slope being proportional to the absolute optical path difference. This potentially solves the problems of phase unwrapping on a pixelper-pixel basis. In this paper, we present an SBInSAR processor and its application using TanDEM-X data over the Nyiragongo volcano.Fil: Derauw, Dominique Maurice. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; Argentina. Centre Spatial de Liège; BélgicaFil: Kervyn, François. Royal Museum Of Central Africa; BélgicaFil: d'Oreye, Nicolas. European Centre For Geodynamics And Seismology; Luxemburgo. National Museum of Natural History; LuxemburgoFil: Smets, Benoit. Royal Museum Of Central Africa; Bélgica. European Centre For Geodynamics And Seismology; Luxemburgo. Vrije Unviversiteit Brussel; BélgicaFil: Albino, Fabien. Royal Museum Of Central Africa; BélgicaFil: Barbier, Christian. Centre Spatial de Liège; BélgicaAdvances in the Science and Applications of SAR Interferometry and Sentinel-1 InSAR WorkshopFrascatiItaliaEuropean Space Agenc

The FABSPACE 2.0 Project For Geodata-Driven Innovation

Now that the Galileo and Copernicus satellite programmes are entering their operational phase, innovation possibilities in the field of satellite data driven applications are getting wider. Thanks to these two massive investments in technology, European and worldwide companies are starting to benefit from increasing, regular and cheaper (not to say free of charge) data flows, which could lead to the development of new and innovative applications and services in an incredibly vast range of markets, including non-space markets. The exploitation of satellite data, as well as open data (from public authorities in particular) has the potential to generate a lot of innovative solutions. In this context the FabSpace 2.0 project aims at putting the Universities at the front line for the take-off of Earth Observation based applications in Europe and worldwide. This can be pursued by hosting and animating open places dedicated to space and geodata-driven innovation where young developers from the civil society, experienced developers from industry or academic and research institutes, public administrations as well as civil organizations can meet, work together and co-create new tools and business models. They can create an ecosystem fitting (and developed according to) the particularities of geodata-driven innovation, in particular for the emergence of Space data downstream services. In this innovative environment, innovation is driven by the needs of users through the involvement of civil society in the innovation process and in the definition of new challenges. Moreover the actors making innovation will be anonymous civilians (students and researchers in particular) and will thus be at the same time developers and end-users of the applications they develop. That is why the FabSpace 2.0 project is expected to improve the capacity of Universities to generate more innovations and generate positive socio-economic impacts. All partner universities are centers of excellence in research in the field of geomatics and space based information. They are not only offering a highly-qualified human capital likely to generate innovation, but also providing open access to data generated within previous research works. Thus the FabSpace 2.0 project can be a particularly relevant opportunity for research teams to make a step forward towards Science 2.0

BelSAR : the first Belgian airborne campaign for L-band, full polarimetric bistatic and interferometric SAR acquisitions over an agricultural site in Belgium

The BelSAR airborne campaign was set up to prepare for future bistatic and interferometric SAR missions. The objective was to acquire L-band, full-polarimetric signatures by two airplanes, flying in various bistatic and interferometric geometries. The scientific scope was focused on agriculture and soil humidity, and the region of interest was part of the Belgian BELAIR HESBANIA test site, located close to Gembloux. Five campaigns took place between May and September 2018. Ground devices were deployed and ground measurements were obtained simultaneously to the imaging passes. The results will be exploited in a scientific project to be initiated in 2019.BelSA

Empirical Removal of Tides and Inverse Barometer Effect on DInSAR From Double DInSAR and a Regional Climate Model

Ice shelves-the floating extensions of the Antarctic ice sheet-regulate the Antarctic contribution to sea-level rise by restraining the grounded ice flowing from upstream. Therefore, ice-shelf change (e.g., ice-shelf thinning) results in accelerated ice discharge into the ocean, which has a direct effect on sea level. Studying ice-shelf velocity allows the monitoring of the ice shelves' stability and evolution. Differential synthetic aperture radar interferometry (DInSAR) is a common technique from which highly accurate velocity maps can be inferred at high resolution. Because ice shelves are afloat, small sea-level changes-i.e., ocean tides and varying atmospheric pressure (aka inverse barometer effect) lead to vertical displacements. If not accounted for in the interferometric process, these effects will induce a strong bias in the horizontal velocity estimation. In this article, we present an empirical DInSAR correction technique from geophysical models and double DInSAR, with a study on its variance propagation. The method is developed to be used at large coverage on short timescales, essential for the near-continuous monitoring of rapidly changing areas on polar ice sheets. We used Sentinel-1 SAR acquisitions in interferometric wide and extra -wide swath modes. The vertical interferometric bias is estimated using a regional climate model (MAR) and a tide model (CATS2008). The study area is located on the Roi Baudouin Ice Shelf in Dronning Maud Land, East Antarctica. Results show a major decrease (67 m·a -1 ) in the vertical-induced displacement bias.Fil: Glaude, Quentin. Université Libre de Bruxelles; Bélgica. Université de Liège; BélgicaFil: Amory, Charles. Universite de Liege. Faculty Of Applied Sciences.; BélgicaFil: Berger, Sophie. Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung; Alemania. Université Libre de Bruxelles; BélgicaFil: Derauw, Dominique Maurice. Universidad Nacional de Río Negro. Sede Alto Valle. Instituto de Investigaciones en Paleobiología y Geología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pattyn, Frank. Vrije Unviversiteit Brussel; Bélgica. Université Libre de Bruxelles; BélgicaFil: Barbier, Christian. Université de Liège; BélgicaFil: Orban, Anne. Université Catholique de Louvain; Bélgic