74 research outputs found
Bayesian data fusion in environmental sciences : theory and applications
No full textDuring the last thirty years, new technologies have contributed to a drastic increase of the amount of data in environmental sciences. Monitoring networks, remote sensors, archived maps and large databases are just few examples of the possible information sources responsible for this growing amount of information. For obvious reasons, it might be interesting to account for all these information when dealing with a space-time prediction/estimation context. In environmental sciences, measurements are very often sampled scarcely over space and time. Geostatistics is the field that investigates variables in a space-time context. It includes a large number of methods and approaches that all aim at providing space-time predictions (or interpolations) for variables scarcely known in space and in time by accounting for space-time dependance between these variables. As a consequence, geostatistics methods are relevant when dealing with the processing and the analysis of environmental variables in which space and time play an important role. As direct consequence of the increasing amount of data, there is an important diversity in the information (e.g. different nature, different uncertainty). These issues have recently motivated the emergence of the concept of data fusion. Broadly speaking, the main objective of data fusion methods is to deal with various information sources in such a way that the final result is a single prediction that accounts for all the sources at once. This enables thus to conciliate several and potentially contradictory sources instead of having to select only one of them because of a lack of appropriate methodology. For most of existing geostatistics methods, it is quite difficult to account for a potentially large number of different information sources at once. As a consequence, one has often to opt for only one information source among all the available sources. This of course leads to a dramatic loss of information. In order to avoid such choices, it is thus relevant to get together the concepts of both data fusion and geostatistics in the context of environmental sciences. The objectives of this thesis are (i) to develop the theory of a Bayesian data fusion (BDF) framework in a space-time prediction context and (ii) to illustrate how the proposed BDF framework can account for a diversity of information sources in a space-time context. The method will thus be applied to a few environmental sciences applications for which (i) crucial available information sources are typically difficult to account for or (ii) the number of secondary information sources is a limitation when using existing methods. Reproduced by permission of Springer. P. Bogaert and D. Fasbender (2007). Bayesian data fusion in a spatial prediction context: a general formulation. Stoch. Env. Res. Risk. A., vol. 21, 695-709. (Chap. 1). © 2008 IEEE. Reprinted, with permission, from D. Fasbender, J. Radoux and P. Bogaert (2008). Bayesian data fusion for adaptable image pansharpening. IEEE Trans. Geosci. Rem. Sens., vol. 46, 1847-1857. (Chap. 3). © 2008 IEEE. Reprinted, with permission, from D. Fasbender, D. Tuia, P. Bogaert and M. Kanevski (2008). Support-based implementation of Bayesian data fusion for spatial enhancement: applications to ASTER thermal images. IEEE Geosci. Rem. Sens. Letters, vol. 6, 598-602. (Chap. 4). Reproduced by permission of American Geophysical Union. D. Fasbender, L. Peeters, P. Bogaert and A. Dassargues (2008). Bayesian data fusion applied to water table spatial mapping. Accepted for publication in Water Resour. Res. (Chap. 5)(AGRO 3) -- UCL, 200
Bayesian Data Fusion for water table interpolation: incorporating a hydrogeological conceptual model in kriging
No full textpeer reviewedThe creation of a contour map of the water table in an unconfined aquifer based on head measurements is often the first step in any hydrogeological study. Geostatistical interpolation methods (e.g. kriging) may provide exact interpolated groundwater levels at the measurement locations, but often fail to represent the hydrogeological flow system. A physically based, numerical groundwater model with spatially variable parameters and inputs is more adequate in representing a flow system. Due to the difficulty in parameterization and solving the inverse problem however, an often considerable difference between calculated and observed heads will remain.
In this study the water table interpolation methodology presented by Fasbender et al. (2008), in which the results of a kriging interpolation are combined with information from a drainage network and a Digital Elevation Model (DEM), using the Bayesian Data Fusion framework (Bogaert and Fasbender, 2007), is extended to incorporate information from a tuned analytic element groundwater model. The resulting interpolation is exact at the measurement locations while the shape of the head contours is in accordance with the conceptual information incorporated in the groundwater flow model.
The Bayesian Data Fusion methodology is applied to a regional, unconfined aquifer in Central Belgium. A cross-validation procedure shows that the predictive capability of the interpolation at unmeasured locations benefits from the Bayesian Data Fusion of the three data sources (kriging, DEM and groundwater model), compared to the individual data sources or any combination of two data sources
Selected Principles, Elements and Experiences of Privatisation in Germany
No full textIn most states with market oriented economic systems privatisation plays an important role in the political discussion, mainly due to the fundamental problem of all economic systems, which is scarcity of available resources. The responsible politicians try to improve the allocation of scarce resources and to increase the financial possibilities for needed development investments by creating an adequate macroeconomic framework and a business-friendly environment. Within the scope of these efforts the production of goods and commercial services by state-owned enterprises only plays a very limited role. The state would be best advised to leave these functions to the, in this regard, more efficient private sector. The public sector should concentrate its respective efforts only on the production of so-called Public Goods and, for political reasons, eventually on some sub-sectors, which are essential for the security of the country. Nearly all market economies and especially states which are in the transitional process from more centrally administered to market oriented economic systems, have room for manoeuvre towards privatisation of state-owned enterprises. Privatisation facilitate the improvement of factor allocation and the reduction of budget constraints, not only by the way of sales revenues but also by creating a broader tax-base, decreasing the need to provide subsidies and, last but not least, mobilising private resources for the aimed development-process. This is also true for the Republic of India as well as for the Federal Republic of Germany. However, privatisation causes not only advantages for the economic systems and the public budgets, but also some economic and financial costs. These costs have to be reduced as much as possible by an efficient target-oriented policy. Although the corresponding policies and experiences in one country can hardly be a blueprint for another country, a policy-dialogue at various levels about privatisation and on the underlying legal and economic frameworks is helpful for all involved parties. The exchange of experiences can also contribute to the avoidance of disappointments and setbacks that could jeopardise the privatisation policy introduced. Relating to the above the Government of India noticed: "Thus, while one would do well to learn from the successful experience, one would have to be careful of the pitfalls as well. In the final analysis, while experience of other countries is available by the way of guidance, one would have to evolve one's own techniques, best suited to the level of development of the country. ... The historic, cultural and institutional context influences the way in which and the pace at which privatisation is implemented" (Ministry of Disinvestment 2003, p.1). Experience sharing between experts of different countries is an appropriate way of learning from each other and avoiding the disadvantages of blue prints at the same time. On initiative of the Ministers of Finance of the Republic of India and the Federal Republic of Germany, both governments agreed, therefore, to enhance the exchange of experiences about disinvestment/privatisation in the framework of economic cooperation. The Ministry of Disinvestment (since June 2004: Department of Disinvestment in the Ministry of Finance) and the Bundesministerium fuer wirtschaftliche Zusammenarbeit und Entwicklung, BMZ, (Federal Ministry for Economic Cooperation and Development) are the responsible authorities. The German contributions will be provided by the Deutsche Gesellschaft fuer Technische Zusammenarbeit, GTZ, (German Agency for Technical Cooperation) on behalf of BMZ. This Report gives an overview of selected principles, elements and experiences of privatisation in Germany, with special reference to the new Federal States in East Germany and under consideration of selected aspects in neighbouring countries. The intention is not to present a complete abstract, but to provide a discussion basis for identifying starting points for a future dialogue about lessons learnt. This paper was elaborated by the Hamburg Institute of International Economics (HWWA) at the instigation of Sanjeev S. Ahluwalia, IAS, (Department of Disinvestment) and Dr. Dietrich Kebschull (GTZ). The author would like to express his sincere thanks to both of them as well as to Gunnar Geyer, Carsten Hefeker, Britta Jens and to Rasul Shams (all HWWA) for their valuable suggestions.Political Economy,
Geostatistical methods in water resources
No full textWater is the most essential resource for the presence of life. Consequently, humanity is completely dependent on this natural resource so that an accurate estimation of both the quantity and the quality of water resources is crucial. Unfortunately, as it is the case for many natural resources, the available data are generally scarcely observed over space and time which geopardizes a proper and accurate estimation of water resources. Consequently, there is thus a real need for methods that can deal with such incomplete datasets.
Incidentally, geostatistics has been developed for the analysis of scarcely observed variables in a space-time context. It gathers numerous methods and approaches that all aim at providing space-time estimations for the variables at ungauged location by accounting for the space-time dependence between these variables and those at gauged location.
This paper intends to present, through various examples of applications, how the geostatistical methods have contributed to a better understanding of water resources around the world. Each section is dedicated to a particular water resource and regroups the different applications in which geostatistics methods have been applied. These sections aren’t meant to be exhaustive but illustrative. A final section presenting a list of useful software and toolboxes has also been added.JRC.H.4 - Monitoring Agricultural Resource
Remote sensing monitoring of land restoration interventions in semi-arid environments with a before–after control-impact statistical design
No full textRestoration interventions to combat land degradation are carried out in arid and semi-arid areas to improve vegetation cover and land productivity. Evaluating the success of an intervention over time is challenging due to various constraints (e.g. difficult-to-access areas, lack of long-term records) and the lack of standardised and affordable methodologies. We propose a semi-automatic methodology that uses remote sensing data to provide a rapid, standardised and objective assessment of the biophysical impact, in terms of vegetation cover, of restoration interventions. The Normalized Difference Vegetation Index (NDVI) is used as a proxy for vegetation cover. Recognising that changes in vegetation cover are naturally due to environmental factors such as the inter-annual climate variability and the seasonal vegetation development cycle, conclusions about the success of the intervention cannot be drawn by focussing on the intervention area only. We therefore use a comparative method that analyses the temporal variations (before and after the intervention) of the NDVI of the intervention area with respect to multiple control sites that are automatically and randomly selected from a set of candidates that are similar to the intervention area. Similarity is defined in terms of class composition as derived from an ISODATA classification of the imagery before the intervention. The method provides an estimate of the magnitude of the differential change in the intervention area and the statistical significance of the no-change hypothesis test. As a case study, the methodology is applied to 15 restoration interventions carried out within the framework of the Great Green Wall for the Sahara and the Sahel Initiative in Senegal. The impact of the interventions is analysed using data at two different resolutions: 250 m for the Moderate Resolution Imaging Spectroradiometer and 30 m for the Landsat mission. Results show that a significant improvement in vegetation cover was detectable only in one third of analysed interventions, which is consistent with independent qualitative assessments based on field observations and visual analysis of high resolution imagery. The pros and cons of using the two data sources are discussed.JRC.D.5 - Food Securit
Updating Scarce High Resolution Images with Time Series of Coarser Images : a Bayesian Data Fusion Solution
No full textRain in Rome, Rain in Hof. Natural Disasters and their Interpretations in Enoch Widmann’s ›Chronik der Stadt Hof‹
No full textDer vorliegende Beitrag widmet sich ausgewählten Passagen über Wetterereignisse in Enoch Widmanns ›Chronik der Stadt Hof‹ (1615), die zum Teil durch die vollständige Neuausgabe (2015) erstmals zugänglich gemacht wurden. Die für ihre narrativen Elemente geschätzte Stadtchronik des Protestanten Widmann handelt, einer Weltchronik gleich, zunächst Ereignisse aus dem spätantiken und frühmittelalterlichen Rom ab. Ein Vergleich von Passagen, die Wetterereignisse in Vergangenheit und (Widmanns) Gegenwart betreffen, führt zu der Erkenntnis, dass der Verfasser die Ereignisse des 16. Jahrhunderts – im Gegensatz zu den spätantiken – im Anschluss an Melanchthon, auf den er sich beruft, durchweg als Vorzeichen des Weltgeschehens begreift.The following article is dedicated to chosen passages concerning weather events in Enoch Widmann’s ›Chronik der Stadt Hof‹ (Chronicle of the City of Hof) (1615), some of which have been made accessible for the first time by the complete new edition (2015). The city chronicle by the Protestant Widmann, which is valued for its narrative elements, initially deals with events from late antique and early medieval Rome, similar to a world chronicle. A comparison of the passages relating to weather events in the past and (Widmann’s) present leads to the realization that the author consistently understands the events of the 16th century – in contrast to those of late antiquity – as omens of world events, following Melanchthon, to whom he refers
Discriminating sources of nitrate pollution in an unconfined sandy aquifer
No full textCorrectly assessing the origin of groundwater pollution is an important prerequisite for efficient groundwater management. In this paper, statistical modelling tools are applied to discriminate the sources of nitrate pollution in the unconfined deep sandy aquifer of the Brusselian sands (Belgium). Multiple regression and regression tree were compared to identify the factors affecting the nitrate concentration in this vulnerable groundwater body. The explanatory factors were related to land and land use properties in the capture zone. The tree model and the low fitting power of the multiple regression model showed the highly complex interaction pattern between explanatory variables. In the region, one explicative variable taken alone could not be considered responsible for the groundwater pollution by nitrate. However, both methods indicated the negative influence of residential land on the nitrate concentrations and a slight protective effect of low slope values. Furthermore, we showed the importance of delineating capture zones on the basis of topography, the type of monitoring station and a simplified water mass balance, compared to circular capture zones centered on the monitoring stations. (C) 2009 Published by Elsevier B.V
Analysis of the sampling representativeness for the Land Parcel Identification System Quality Assurance
No full textAfter its 2016 performance audit on the Land Parcel Identification System (LPIS), the European Court of Auditors recommended that the Commission should carry out a cost-benefit analysis in order to determine whether the representativeness of QA samples could be improved so that a better coverage of the population of parcels in LPIS be achieved. This report holds the results of that analysis.
An appropriate indicator for representativeness was developed and benchmarked. That indicator, “percentage of the population in the 95% central probability interval (PCPI)” was then applied to the actual samples of the past to measure their performance. Additionally, the simulation of several sampling scenarios allowed to assess whether sub-optimal conditions could be remediated by the appropriate mitigation measures.
The results reconfirmed that the initial approach of spatial stratification does not interfere with the representativeness in se, but it also found that the current implementation could leave a few territories with some residual effect from the implied spatial clustering. This potential weakness was addressed by improving the resolution of the stratification control layer, ensuring a minimum set of clusters as well as introducing stratified random sampling. Simulations demonstrated these combined remedies were effective for nearly all Member States and regions. Cyprus and Luxemburg missed the target, but only just.
The revised methodology led to a 15 percent increase of the number of control zones over Europe, but did not require any procedural modification or other additional inspection workload for the Member States. This revised sampling methodology thus considers the Court’s cost-benefit concerns and has been fully implemented for the 2017 LPIS QA campaign.JRC.D.5 - Food Securit
- …
