Discriminating small wooded elements in rural landscape from aerial photography: a hybrid pixel/object-based analysis approach

While small, fragmented wooded elements do not represent a large surface area in agricultural landscape, their role in the sustainability of ecological processes is recognized widely. Unfortunately, landscape ecology studies suffer from the lack of methods for automatic detection of these elements. We propose a hybrid approach using both aerial photographs and ancillary data of coarser resolution to automatically discriminate small wooded elements. First, a spectral and textural analysis is performed to identify all the planted-tree areas in the digital photograph. Secondly, an object-orientated spatial analysis using the two data sources and including a multi-resolution segmentation is applied to distinguish between large and small woods, copses, hedgerows and scattered trees. The results show the usefulness of the hybrid approach and the prospects for future ecological applications

Diffusion and robustness of boundary feedback stabilization of hyperbolic systems

We consider the problem of boundary feedback control of single-input-single-output (SISO) one-dimensional linear hyperbolic systems when sensing and actuation are anti-located. The main issue of the output feedback stabilization is that it requires dynamic control laws that include delayed values of the output (directly or through state observers) which may not be robust to infinitesimal uncertainties on the characteristic velocities. The purpose of this paper is to highlight some features of this problem by addressing the feedback stabilization of an unstable open-loop system which is made up of two interconnected transport equations and provided with anti-located boundary sensing and actuation. The main contribution is to show that the robustness of the control against delay uncertainties is recovered as soon as an arbitrary small diffusion is present in the system. Our analysis also reveals that the effect of diffusion on stability is far from being an obvious issue by exhibiting an alternative simple example where the presence of diffusion has a destabilizing effect instead.Comment: 21 page

DISSIPATIVE BOUNDARY CONDITIONS FOR ONE-DIMENSIONAL NONLINEAR HYPERBOLIC SYSTEMS

International audienceWe give a new sufficient condition on the boundary conditions for the exponential stability of one-dimensional nonlinear hyperbolic systems on a bounded interval. Our proof relies on the construction of an explicit strict Lyapunov function. We compare our sufficient condition with other known sufficient conditions for nonlinear and linear one-dimensional hyperbolic systems

Etre et avoir à Kinshasa

Expériences de reportage pour la radio-télévision belge au Congo de 1980 à 2003. Il n’y a pas de progression logique dans le déroulement des faits mais une succession d’expériences originales, discontinues, peu prévisibles, témoignant sans doute d’un fonctionnement similaire de la société congolaise, souvent qualifié d’informel. Cette succession d’expériences pose une question lancinante : comment voir sans être vu ? Comment observer sans être soi-même observé, sans déranger l’ordre et le désordre des choses ? Est-il possible pour des Belges de filmer des Congolais, sans qu’interfère leur passé commun ? La vraie constante dans ces expériences est la relation des Congolais à la caméra professionnelle. Celle-ci est surtout perçue comme un objet étranger, blanc, extérieur, comme une caméra de surveillance, un objet décidément post-colonial, face auquel il faut se composer une attitude de défi et de fierté. L’auteur propose d’organiser ses tournages comme un échange, un donnant-donnant, où l’argent occupe une place importante, mais pas essentielle : qu’ils soient payés ou pas, les Congolais filmés sont finalement les seuls à décider de ce qu’ils donnent à la caméra. En contrôlant leur image, ils s’approprient une part du film.Experience as reporter for Belgian radio and television in Congo between 1980 and 2003. There is no logical progression in the unfolding of events but a succession of original, fragmented, unpredictable experiences probably testifying to a similar functioning of Congolese society, usually qualified as informal. This succession of experiences raises some troublesome questions: How to see without being seen? How to observe without yourself being observed, without upsetting the order and disorder of things? Is it possible for Belgians to film Congolese without their common past getting in the way? The unwavering fact in these experiences is the relationship that Congolese have with a professional camera. This thing is perceived as a foreign, white, outside object, like a surveillance camera, a resolutely post-colonial object, opposite which an attitude of defiance and pride is necessary. The author organises his reports like an exchange of give-and-take where money plays an important – but not essential – role. Whether they are paid or not, filmed Congolese are ultimately alone in deciding what they give to the camera. By controlling their image, they appropriate part of the film

The global tree carrying capacity (keynote)

editorial reviewe

Interactive climate factors restrict future increases in spring productivity of temperate trees

peer reviewe

Open-source mapping and services for Web-based land-cover validation

Monitoring land-cover changes on sites of conservation importance allows environmental problems to be detected, solutions to be developed and the effectiveness of actions to be assessed. However, the remoteness of many sites or a lack of resources means these data are frequently not available. Remote sensing may provide a solution, but large-scale mapping and change detection may not be appropriate, necessitating site-level assessments. These need to be easy to undertake, rapid and cheap. We present an example of a Web-based solution based on free and open-source software and standards (including PostGIS, OpenLayers, Web Map Services, Web Feature Services and GeoServer) to support assessments of land-cover change (and validation of global land-cover maps). Authorised users are provided with means to assess land-cover visually and may optionally provide uncertainty information at various levels: from a general rating of their confidence in an assessment to a quantification of the proportions of land-cover types within a reference area. Versions of this tool have been developed for the TREES-3 initiative (Simonetti, Beuchle and Eva, 2011). This monitors tropical land-cover change through ground-truthing at latitude / longitude degree confluence points, and for monitoring of change within and around Important Bird Areas (IBAs) by Birdlife International and the Royal Society for the Protection of Birds (RSPB). In this paper we present results from the second of these applications. We also present further details on the potential use of the land-cover change assessment tool on sites of recognised conservation importance, in combination with NDVI and other time series data from the eStation (a system for receiving, processing and disseminating environmental data). We show how the tool can be used to increase the usability of earth observation data by local stakeholders and experts, and assist in evaluating the impact of protection regimes on land-cover change