1,721,082 research outputs found
Multi-temporal Crop Surface Models derived from terrestrial laser scanning for accurate plant height measurement and biomass estimation of barley
No full textISSN:0454-129
Spectral comparison of low-weight and UAV-based hyperspectral frame cameras with portable spectroradiometer measurements
No full textISSN:0454-129
Towards precision grazing: Spatio-temporal dynamics of the relation between cattle, vegetation, and arthropods
No full texthttp://dx.doi.org/10.13039/501100002347 Federal Ministry of Education and Research Bonn Offic
UAV-based Imaging of Multispectral Reflectance and Solar-Induced Chlorophyll Fluorescence for Crop Monitoring
No full textThe agri-food sector is facing significant challenges due to climate change, unpredictable weather, and rapid population growth. The growing demand to embrace advanced agricultural systems that boost productivity while mitigating climate impacts requires accurate and reliable crop monitoring techniques. In this context, site-specific farm management and remote sensing have become indispensable. Remote sensing offers real-time information about crop growth and health throughout the growing season at different scales. UAV-based remote sensing, in particular, offers a cost-effective tool for monitoring crop growth and health with high spatiotemporal resolution that enables response to field-scale issues by driving informed decision-making. Our study contributes to this evolving landscape by exploring the potential of UAV-based multispectral imaging in crop monitoring on the field scale.
In the first study, high-resolution imagery from the DJI Phantom 4 multispectral UAV system was employed to monitor the seasonal development of spelt in a biochar-enriched experiment. A straightforward data processing workflow was developed based on an empirical line method to convert raw UAV data to normalized and comparable reflectance maps and calculate various vegetation indices. Results indicated that EVI was the most effective index in relation to the actual yield, indicating better spelt development over the biochar-enriched plots with a full conventional fertilization amount compared to controls that received the same conventional fertilization.
The second study addressed the retrieval of sun-induced fluorescence, F760, from SIFcam, a dual-camera system prototype mounted on a UAV. A comprehensive overview and advancements of the developed methodology for SIFcam imagery, in addition to a second innovative workflow, were presented. The F760 retrieved from the two workflows showed strong correlations with ground-based measurements (R² = 0.92) and moderate correlations with airborne imaging spectrometer HyPlant (R² = 0.56, 0.52 for workflows 1 and 2b, respectively). The SIFcam has shown its capability to effectively disentangle the fluorescence signal from canopy reflectance with a moderate level of accuracy and adequate stability in data collection at the field scale, with less than one-pixel variation between spectral channels in both horizontal and vertical directions.
The third study investigated the potential of integrating SIFcam F760 alongside UAV-based multispectral VIs to characterize and delineate diverse new and old winter wheat cultivars. SIFcam demonstrated a notable potential in capturing the variability of F760 between wheat cultivars with structural and pigment differences. New wheat cultivars generally revealed higher F760, consistent with their higher chlorophyll content, yet old cultivar Banco indicated that canopy architecture could significantly modulate TOC F760, with F760 values comparable to or even exceeding those of certain new cultivars. VIs sensitive to chlorophyll content, particularly TCARI/OSAVI (Cohen's d >= 0.5), outperformed structure-related VIs and F760 for distinguishing the cultivars. SIFcam proved to be a valuable tool for field plant phenotyping and potentially guiding breeding programs
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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