Search results for "look"
showing 10 items of 50 documents
Automatic emulator and optimized look-up table generation for radiative transfer models
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 Automatic Gaussian Process Emulator (AGAPE) methodology combines the interpolation capabilities of Gaussian processes (GPs) with the accurate design of an acquisition function that favors sampling in low density regions and flatness of the interpolation function. We illustrate the good capabilities of the method in toy examples and for the construction of an…
Empirical and physical estimation of Canopy Water Content from CHRIS/PROBA data
2013
20 páginas, 4 tablas, 7 figuras.
Global Sensitivity Analysis of Leaf-Canopy-Atmosphere RTMs: Implications for Biophysical Variables Retrieval from Top-of-Atmosphere Radiance Data.
2019
Knowledge of key variables driving the top of the atmosphere (TOA) radiance over a vegetated surface is an important step to derive biophysical variables from TOA radiance data, e.g., as observed by an optical satellite. Coupled leaf-canopy-atmosphere Radiative Transfer Models (RTMs) allow linking vegetation variables directly to the at-sensor TOA radiance measured. Global Sensitivity Analysis (GSA) of RTMs enables the computation of the total contribution of each input variable to the output variance. We determined the impacts of the leaf-canopy-atmosphere variables into TOA radiance using the GSA to gain insights into retrievable variables. The leaf and canopy RTM PROSAIL was coupled with…
Split-Window Coefficients for Land Surface Temperature Retrieval From Low-Resolution Thermal Infrared Sensors
2008
In this letter, we provide a complete set of split-window coefficients that can be used to retrieve land surface temperature (LST) from thermal infrared sensors onboard the most popular remote-sensing satellites: ERS-ATSR2, ENVISAT-AATSR, Terra/Aqua-MODIS, NOAA series-AVHRR, METOP-AVHRR3, GOES series-IMAGER, and MSG1/MSG2-SEVIRI. The coefficients have been obtained by minimization from an extensive simulated database constructed from MODTRAN radiative transfer code calculations, emissivity spectra extracted from spectral libraries, and spectral response functions of the thermal bands considered. This letter also analyzes the magnitude of the error on the LST retrieval and the contribution t…
Optimizing LUT-based radiative transfer model inversion for retrieval of biophysical parameters using hyperspectral data
2012
Inversion of radiative transfer models using a lookup-table (LUT) approach against hyperspectral data streams leads to retrievals of biophysical parameters such as chlorophyll content (Chl), but necessary optimization strategies are not consolidated yet. Here, various regularization options have been evaluated to the benefit of improved Chl retrieval from hyperspectral CHRIS data, being: i) the role of added noise, ii) the role of multiple best solutions, and iii) the role of applied cost functions in LUT-based inversion. By using data from the ESA-led field campaign SPARC (Barrax, Spain), it was found that introducing noise and opting for multiple best solutions in the inversion considerab…
Enhanced Mathematical Modelling of Interior Permanent Magnet Synchronous Machine Considering Saturation, Cross-Coupling and Spatial Harmonics effects
2020
The Interior Permanent Magnet Synchronous machine (IPMSM) conventional mathematical model is generally employed to investigate and simulate the IPMSM control and drive system behaviour. However, magnetic nonlinearities and spatial harmonics have a substantial influence on the IPMSM electromagnetic behaviour and performances. In order to simulate the IPMSM real electromagnetic behaviour, this paper describes an enhanced mathematical model that takes into account the saturation, cross-coupling and spatial harmonics effects. This model has been implemented in Matlab®/Simulink environment where the electric and magnetic parameters are derived from FEA investigations and implemented by the use o…
Colorimetric Characterization of Mobile Devices for Vision Applications
2015
Purpose: Available applications for vision testing in mobile devices usually do not include detailed setup instructions, sacrificing rigor to obtain portability and ease of use. In particular, colorimetric characterization processes are generally obviated. We show that different mobile devices differ also in colorimetric profile and that those differences limit the range of applications for which they are most adequate. Methods: The color reproduction characteristics of four mobile devices, two smartphones (Samsung Galaxy S4, iPhone 4s) and two tablets (Samsung Galaxy Tab 3, iPad 4), have been evaluated using two procedures: 3D LUT (Look Up Table) and a linear model assuming primary constan…
Numerical implementation of active power flow tracing methods: Practical implications on transmission networks and DR programs support
2015
The goal of this paper is to demonstrate the powerful contribution of the electric active power flow tracing methods on studying the electric transmission systems operating conditions. The tracing methods allow to impute to every generation unit and/or load the responsibility of the power flows of all the elements connected to the network. This study propose the numerical implementation of two different tracing methods on two transmission networks through Matlab® scripts developed on purpose; then the analysis is focused on identifying the loads which mostly affect the power line flows of the system. The results of this analysis point out the loads on which the application of the Demand Res…
The Real Effect of Financial Crises in the European Transition Economies
2010
Working Paper GATE 2009-20; International audience; The aim of this work is to assess the impact of financial crises on output for 11 European transition economies (CEECs). The results suggest that financial crises have a significant and permanent effect, lowering long-term output by about 17 percent. The effect is more important in smaller countries, with relative higher dependence on external financing, and in which the banking sector noticed more important financial disequilibria. We also found that fiscal policy measures have been the most efficient tools in dealing with the crises, while the role of monetary policy instruments has been rather blinded. Exchange rate resulted to be more …
Regarding the shipwreck of others: for a critical visual topography of Mediterranean migration
2019
This article reflects on the relationship between photography and migration from a cultural geography perspective, with particular reference to the visual construction of the Mediterranean border regime. The contemporary aesthetics of Mediterranean migration is one of the domains in which visual and social norms are most closely intertwined. My main purpose is to unveil these processes of mutual (re)production by analysing how photographs forge our everyday perceptions of migration and affect our very ability to produce ethical and political responses to the events they portray. Drawing on a range of fields and approaches, including cultural geography, visual culture studies and postcoloni…