Search results for "Computers"
showing 10 items of 3243 documents
Seasonal variations of leaf area index of agricultural fields retrieved from Landsat data
2008
Abstract The derivation of leaf area index (LAI) from satellite optical data has been the subject of a large amount of work. In contrast, few papers have addressed the effective model inversion of high resolution satellite images for a complete series of data for the various crop species in a given region. The present study is focused on the assessment of a LAI model inversion approach applied to multitemporal optical data, over an agricultural region having various crop types with different crop calendars. Both the inversion approach and data sources are chosen because of their wide use. Crops in the study region (Barrax, Castilla–La Mancha, Spain) include: cereal, corn, alfalfa, sugar bee…
Retrieval of canopy water content of different crop types with two new hyperspectral indices: Water Absorption Area Index and Depth Water Index
2018
Crop canopy water content (CWC) is an essential indicator of the crop’s physiological state. While a diverse range of vegetation indices have earlier been developed for the remote estimation of CWC, most of them are defined for specific crop types and areas, making them less universally applicable. We propose two new water content indices applicable to a wide variety of crop types, allowing to derive CWC maps at a large spatial scale. These indices were developed based on PROSAIL simulations and then optimized with an experimental dataset (SPARC03; Barrax, Spain). This dataset consists of water content and other biophysical variables for five common crop types (lucerne, corn, potato, sugar …
Scenario-based discrimination of common grapevine varieties using in-field hyperspectral data in the western of Iran
2019
Abstract Field spectroscopy is an accurate, rapid and nondestructive technique for monitoring of agricultural plant characteristics. Among these, identification of grapevine varieties is one of the most important factors in viticulture and wine industry. This study evaluated the discriminatory ability of field hyperspectral data and statistical techniques in case of five common grapevine varieties in the western of Iran. A total of 3000 spectral samples were acquired at leaf and canopy levels. Then, in order to identify the best approach, two types of hyperspectral data (wavelengths from 350 to 2500 nm and 32 spectral indices), two data reduction methods (PLSR and ANOVA-PCA) and two classif…
Prototyping Sentinel-2 green LAI and brown LAI products for cropland monitoring.
2022
Abstract For agricultural applications, identification of non-photosynthetic above-ground vegetation is of great interest as it contributes to assess harvest practices, detecting crop residues or drought events, as well as to better predict the carbon, water and nutrients uptake. While the mapping of green Leaf Area Index (LAI) is well established, current operational retrieval models are not calibrated for LAI estimation over senescent, brown vegetation. This not only leads to an underestimation of LAI when crops are ripening, but is also a missed monitoring opportunity. The high spatial and temporal resolution of Sentinel-2 (S2) satellites constellation offers the possibility to estimate …
Land use classification from multitemporal Landsat imagery using the Yearly Land Cover Dynamics (YLCD) method
2011
Abstract Several previous studies have shown that the inclusion of the LST (Land Surface Temperature) parameter to a NDVI (Normalized Difference Vegetation Index) based classification procedure is beneficial to classification accuracy. In this work, the Yearly Land Cover Dynamics (YLCD) approach, which is based on annual behavior of LST and NDVI, has been used to classify an agricultural area into crop types. To this end, a time series of Landsat-5 images for year 2009 of the Barrax (Spain) area has been processed: georeferenciation, destriping and atmospheric correction have been carried out to estimate NDVI and LST time series for year 2009, from which YLCD parameters were estimated. Then…
Crop nitrogen monitoring: Recent progress and principal developments in the context of imaging spectroscopy missions
2020
Abstract Nitrogen (N) is considered as one of the most important plant macronutrients and proper management of N therefore is a pre-requisite for modern agriculture. Continuous satellite-based monitoring of this key plant trait would help to understand individual crop N use efficiency and thus would enable site-specific N management. Since hyperspectral imaging sensors could provide detailed measurements of spectral signatures corresponding to the optical activity of chemical constituents, they have a theoretical advantage over multi-spectral sensing for the detection of crop N. The current study aims to provide a state-of-the-art overview of crop N retrieval methods from hyperspectral data…
Do young graduates with professional and vocational master's degrees regard themselves as competent to hold their jobs ?
2016
En ligne sur http://www.cereq.fr/content/download/16090/129720/file/Trai118.pdf; Professional and vocational courses requiring 5 years' post-secondary study are supposed to meet specific needs for competences in a given area of employment. Young graduates believe they have acquired the specific competences they think their employers require. In their view, the shortfall lies in their general competences. Is this a reason to question the increasingly vocational nature of university courses?
Creativity and Innovation in Technology-Mediated Journalistic Work : Mapping out Enablers and Constraints
2020
This qualitative study examines creativity and innovation in dispersed, journalistic teams. Specifically, we study the factors enabling and constraining creativity and innovation in journalistic work in technology-mediated settings and explore how technology shapes these phenomena in dispersed journalistic teams. The study is motivated by the media industry’s heightened need for creativity and innovation as well as the changing nature of working life where an increasing amount of work is done via information and communication technologies. By closely examining two journalistic teams and their idea sharing and development processes, this study finds that successful creative work and innovati…
Sourcing on the internet: Examining the relations among different phases of online inquiry
2021
This study examined students’ engagement in sourcing throughout online inquiry, that is, when they specified the information need, formulated search queries, evaluated online texts, and composed a written product. Participants were 167 upper secondary school students. Students completed an online inquiry task in a restricted online environment that utilized authentic online texts. Students’ prior topic knowledge and reading fluency was measured and controlled for in the analysis. The results showed that students engaged in sourcing even in the earliest phases of online inquiry. A sequential regression analysis indicated that the more frequently students engaged in sourcing in specifying the…
Online Learning Environments, Scientific Argumentation, and 21st Century Skills
2019
A workshop held at the National Academies in the United States in 2007 highlighted five broad categories of skills that appear valuable across a range of jobs for people working in modern global economies. Engaging students in scientific argumentation can support the development of these 21st century skills. Unfortunately, opportunities are rare in typical classrooms for students to learn how to engage in scientific argumentation. Over the past ten years several online environments have been developed to support students engaging with one another in scientific argumentation. This paper considers how engaging students in scientific argumentation through the activity structures and scripts in…