1,720,987 research outputs found
Mobile LiDAR applications to monitor the urban forest in the city of Hasselt, Belgium
No full textUrban forests provide essential ecosystem services and are key components of urban policy-making. Both accounting for these ecosystem services and effective urban forest management planning, however, requires an upto-date and detailed 3D tree inventory. Conducting and maintaining up-to-date tree inventories often involves field visits and manual recordings. In this study, we demonstrate the applicability of close-range remote sensing in measuring and monitoring tree characteristics over time. A mobile LiDAR system was deployed to collect dense point clouds (1789.92 points/m2) in the city of Hasselt, Belgium. The proposed individual tree detection algorithm obtained a recall score of 0.84, a precision of 0.82 and an F-score of 0.83. The average estimated characteristics were: tree height (H) of 9.84 f 2.68 m, diameter at breast height (DBH) of 0.48 f 0.74 m, crown projection (PA) of 14.87 f 11.60 m2 and crown volume (AV) of 73.59 f 98.42 m3 . For a subset of 47 manually measured trees (r)RMSE values were 0.58 m (259 %) and 0.96 m (10 %) for DBH and H, respectively. Excluding incorrectly segmented trees mainly improved (r)RMSE values of DBH (0.05 m, 21 %) and only had a minor effect on H (0.95 m, 11 %). Two case studies based on multi-temporal MLS-datasets allowed to estimate the volume of pruning biomass and to detect a nest of Asian hornet (Vespa velutina). The obtained results can support both policy-making and operational planning by integrating 3D tree inventories and assessing the effect of management activities.We acknowledge the support of the city administration of Hassel
UAV Imagery to support individual tree management and monitoring
No full textUnoccupied Aerial Vehicles (UAVs) have gained prominence in remote sensing applications, a.o. in individual tree detection (ITD) and management. This study explores the potential of UAV imagery in two key applications: assessing tree health using multispectral data on the one hand and evaluating the impact of different Structure-from-Motion (SfM) software packages on ITD on the other hand. In the first case study, multispectral UAV imagery was collected from an urban park in Belgium. Normalized Difference Red Edge Index (NDRE), oftenly used as a proxy of crop health, was found to be related to traditional visual tree assessments (VTAs), which highlights the potential of UAVs to complement ground surveys by offering a 'top view' perspective. While limitations exist in capturing within-canopy information, such as branch structure, multispectral UAV imagery can still be useful in detecting early signs of stress, presenting an objective supplement to subjective expert-driven VTAs. In the second case study, the impact of SfM software packages on ITD was investigated using existing imagery. Pix4DMapper, Agisoft Metashape and WebODM were employed to generate 3D point clouds for individual tree delineation. Pix4DMapper and Agisoft Metashape outperformed WebODM in terms of correctly classified trees, demonstrating higher recall, precision, and F-scores. WebODM exhibited a higher fraction of false negatives and false positives, and detected smaller trees on average. The findings emphasize the importance of SfM software selection in optimizing the accuracy of ITD from UAV-derived data. In conclusion, this research underscores the potential of UAVs in enhancing tree inventories, both in an urban or forest related context. The combination of multispectral imagery for tree health assessment and careful consideration of SfM software choices for ITD can contribute valuable insights to (urban) forestry management
Digital mapping of soil organic carbon using drone remote sensing
No full textSoil organic carbon (SOC) content is a key indicator of soil health informing about sustainable land management practices, but parcel-wide SOC mapping is challenging as it requires high-resolution data. Unoccupied Aerial Vehicles (UAVs) can collect data with cm-resolution but are not yet fully ready to be practically implemented. The aim of this study is to provide more insights in the explanatory capabilities of UAV-derived spectral and topographical variables. To this end, mixed models were employed to estimate the SOC content of three agricultural parcels with different crop types in Greece. Results showed variations in SOC content among parcels, with a vineyard and a kiwi orchard having higher values compared to a peach orchard. All models, containing topographical and/or spectral variables, explained 81% of SOC content variation of the training dataset. Besides crop type, other topographical and spectral variables were identified as significant predictors. The study emphasizes the feasibility of UAV data and specific modeling techniques for accurate SOC estimation at the parcel level, providing valuable insights for precision agriculture. The findings recommend further exploration, including machine-learning approaches in future studies
Room for renewables: A GIS-based agrivoltaics site suitability analysis in urbanized landscapes
No full textCONTEXT: Flanders, a densely populated region in Belgium, faces challenges in balancing agricultural production with renewable energy targets. Agrivoltaic systems combine solar energy and agricultural activity on the same field and can increase land productivity while simultaneously expanding the share of renewables. However, its potential and implications for the region is geographically complex. OBJECTIVE: This research aims to assess the suitability of Flanders' 658,000 ha agricultural land for agrivoltaic systems, using a geographical multi criteria decision analysis (MCDA), considering environmental, technical, agronomic, and cultural criteria to optimize land use for simultaneous food and energy production. METHODS: We describe a Geographic information system Multiple-criteria decision analysis (GIS-MCDA) using QGis-software. Expert stakeholder input was incorporated by applying the pairwise comparison method from the analytical hierarchical process (AHP). Criterion weights are applied to seven classifiers: irradiance, soil suitability, slope, orientation (aspect), crop type, flood risk and distance to roads/grid. Areas with particular societal, ecological, economic, and historical importance are excluded. The resulting scores are then placed in their agronomic and energy context. RESULTS AND CONCLUSION: Our analysis indicates that 60.4 % of Flanders' farmland is well suited for agrivoltaic development, and that 9 % of farmland under AV would suffice to meet future energy targets in combination with rooftop PV. After our analysis, 11.5 % of total agricultural land was classified as less suitable, 28.74 % as somewhat suitable, 19.40 % as suitable and 12.22 % as very suitable. SIGNIFICANCE: Transitioning away from fossil fuels requires a multi-facetted approach. Agrivoltaic systems can contribute to this shift, opening up additional land without significantly compromising farm revenue. This study presents insights into the feasibility and geographic potential of agrivoltaic systems in densely populated regions with intensive agriculture like Flanders and can serve as a base for future discussion regarding dual land use planning decisions locally and abroad.We would like to thank all participants of the survey, as well as Marleen Gysen and Tom Schaeken (Boerenbond) for organizing the dissemination events making it possible to reach the appropriate expert audience. Special thanks also to Gabriele Torma (Aarhus University) for helping set up the survey. Also, thanks to Wim Clymans (VITO) for providing feedback on the draft manuscript and Andreas Harlander (Krinner GMBH) for the use of their photo. This work was supported by the European Union’s Horizon 2020 research and innovation programme project “HyPErFarm” [grant number 101000828]; a Flanders Innovation and Entrepreneurship (VLAIO)
“TETRA” grant project “Agrivoltaics” [grant number HBC.2019.2049]; and a VLAIO LA-traject grant “Agri-PV” [grant number HBC.2022.0920]. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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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