Search results for "Geological"
showing 10 items of 565 documents
Automatic Emulation by Adaptive Relevance Vector Machines
2017
This paper introduces an automatic methodology to construct emulators for costly radiative transfer models (RTMs). The proposed method is sequential and adaptive, and it is based on the notion of the acquisition function by which instead of optimizing the unknown RTM underlying function we propose to achieve accurate approximations. The proposed methodology combines the interpolation capabilities of a modified Relevance Vector Machine (RVM) with the accurate design of an acquisition function that favors sampling in low density regions and flatness of the interpolation function. The proposed Relevance Vector Machine Automatic Emulator (RAE) is illustrated in toy examples and for the construc…
Systematic Assessment of MODTRAN Emulators for Atmospheric Correction
2021
Atmospheric radiative transfer models (RTMs) simulate the light propagation in the Earth's atmosphere. With the evolution of RTMs, their increase in complexity makes them impractical in routine processing such as atmospheric correction. To overcome their computational burden, standard practice is to interpolate a multidimensional lookup table (LUT) of prestored simulations. However, accurate interpolation relies on large LUTs, which still implies large computation times for their generation and interpolation. In recent years, emulation has been proposed as an alternative to LUT interpolation. Emulation approximates the RTM outputs by a statistical regression model trained with a low number …
Adaptive Sequential Interpolator Using Active Learning for Efficient Emulation of Complex Systems
2020
Many fields of science and engineering require the use of complex and computationally expensive models to understand the involved processes in the system of interest. Nevertheless, due to the high cost involved, the required study becomes a cumbersome process. This paper introduces an interpolation procedure which belongs to the family of active learning algorithms, in order to construct cheap surrogate models of such costly complex systems. The proposed technique is sequential and adaptive, and is based on the optimization of a suitable acquisition function. We illustrate its efficiency in a toy example and for the construction of an emulator of an atmosphere modeling system.
Approximating Empirical Surface Reflectance Data through Emulation: Opportunities for Synthetic Scene Generation
2019
Collection of spectroradiometric measurements with associated biophysical variables is an essential part of the development and validation of optical remote sensing vegetation products. However, their quality can only be assessed in the subsequent analysis, and often there is a need for collecting extra data, e.g., to fill in gaps. To generate empirical-like surface reflectance data of vegetated surfaces, we propose to exploit emulation, i.e., reconstruction of spectral measurements through statistical learning. We evaluated emulation against classical interpolation methods using an empirical field dataset with associated hyperspectral spaceborne CHRIS and airborne HyMap reflectance spectra…
Comparison Between Fractional Vegetation Cover Retrievals from Vegetation Indices and Spectral Mixture Analysis: Case Study of PROBA/CHRIS Data Over …
2009
Abstract: In this paper we compare two different methodologies for Fractional Vegetation Cover (FVC) retrieval from Compact High Resolution Imaging Spectrometer (CHRIS) data onboard the European Space Agency (ESA) Project for On-Board Autonomy (PROBA) platform. The first methodology is based on empirical approaches using Vegetation Indices (VIs), in particular the Normalized Difference Vegetation Index (NDVI) and the Variable Atmospherically Resistant Index (VARI). The second methodology is based on the Spectral Mixture Analysis (SMA) technique, in which a Linear Spectral Unmixing model has been considered in order to retrieve the abundance of the different constituent materials within pixe…
Early-stage thermal performance design of thermo-active walls implemented in underground infrastructures
2022
Abstract Energy geostructures (EGs) represent an innovative technology in the sustainable energy agenda and are useful for satisfying the energy needs of the built environment. They are usually involving geostructures such as piles, walls, tunnels, shafts, and sewers. The application of such technology to infrastructure projects may have considerable thermal potential because of the large surfaces that can be thermally activated. This study focuses on thermo-active walls (energy walls, EWs), which are retaining structures used to sustain the sides of excavations. Key features related to their thermal design are examined, and a design methodology is proposed. The heat-exchange modes involvin…
Increasing understanding and confidence in THM simulations of engineered barrier systems
2020
Previous studies on the modelling of coupled thermo-hydro-mechanical (THM) processes in bentonite-based engineered barrier systems (EBSs) showed the sensitivity of the output quantities to changes in the input parameters. To investigate the effects of uncertainties on the modelling results, to improve the understanding of the coupled processes active in the repository near field and to gain in-depth understanding of model uncertainties of different codes, a sensitivity analysis and code comparison of EBS simulations was performed within the Task Force on Engineered Barrier Systems. The analysis included variations in material parameter values, boundary and initial conditions, considered phy…
Hand Held 3D Scanning for Cultural Heritage: Experimenting Low Cost Structure Sensor Scan
2017
In the last years 3D scanning has become an important resource in many fields, in particular it has played a key role in study and preservation of Cultural Heritage. Moreover today, thanks to the miniaturization of electronic components, it has been possible produce a new category of 3D scanners, also known as handheld scanners. Handheld scanners combine a relatively low cost with the advantage of the portability. The aim of this chapter is two-fold: first, a survey about the most recent 3D handheld scanners is presented. As second, a study about the possibility to employ the handheld scanners in the field of Cultural Heritage is conducted. In this investigation, a doorway of the Benedictin…
Hydraulic Models and Finite Elements for Monitoring of an Earth Dam, by Using GNSS Techniques
2016
This work gives a comparison between different mathematicalmodels for the evaluation of the movements of an earthendam situated between Bivona and Alessandria della Rocca, inthe province of Agrigento (AG), Italy. The models selected areof a hydraulic nature, already tested on concrete dams, andfinite elements models which, on the contrary, exploit geotechnicalparameters. The results obtained from the comparisonof the displacement planimetric components and the relativetime series of data over a period of two years appear to befully satisfactory, in fact using both models of a hydraulic andgeotechnical nature, we reach residues of just mm. To supportthis work, a monitoring procedure using GN…
International Journal of Remote Sensing RAQRS V special issue
2019
This special issue has its origins in the Fifth International Symposium on Recent Advances in Quantitative Remote Sensing (RAQRS) held in Torrent, Spain, from 18 to 22 September 2017. Approximately...