1,720,970 research outputs found
Forestry parameter retrieval from texture in CARABAS VHF-band SAR images
No full textMethods for retrieval of the stem volume, dominant tree height, and dominant tree diameter values using CARABAS images are presented. Both intensity and its texture can be used, but texture detects sparse, low stem volume forests overlooked by the intensity. The texture parameters used are the zero and first-order constants of the log-log regression of the standard deviation of the intensity and the distance over which it is determined. The accuracy of the stem volume estimates is of the order of the ground truth. The dominant diameter and height values are less accurate.</p
Nation-wide clear-cut mapping in Sweden using ALOS PALSAR strip images
Get PDFAdvanced Land Observing Satellite (ALOS) Phased Array L-band type Synthetic Aperture Radar (PALSAR) backscatter images with 50 m pixel size (strip images) at HV-polarization were used to map clear-cuts at a regional and national level in Sweden. For a set of 31 clear-cuts, on average 59.9% of the pixels within each clear-cut were correctly detected. When compared with a one-pixel edge-eroded version of the reference dataset, the accuracy increased to 88.9%. With respect to statistics from the Swedish Forest Agency, county-wise clear-felled areas were underestimated by the ALOS PALSAR dataset (between 25% and 60%) due to the coarse resolution. When compared with statistics from the Swedish National Forest Inventory, the discrepancies were larger, partly due to the estimation errors from the plot-wise forest inventory data. In Sweden, for the time frame of 2008–2010, the total area felled was estimated to be 140,618 ha, 172,532 ha and 194,586 ha using data from ALOS PALSAR, the Swedish Forest Agency and the Swedish National Forest Inventory, respectively. ALOS PALSAR strip images at HV-polarization appear suitable for detection of clear-felled areas at a national level; nonetheless, the pixel size of 50 m is a limiting factor for accurate delineation of clear-felled areas
Evaluation of remote sensing techniques for estimation of forest variables at stand level
Get PDFThere is a continuous need for accurate forest description. Forest data at stand level is required in forestry planning, in particular when scheduling treatments within the next few years. Collection of forest data is typically acquired with subjective surveying methods in the field. However, field work is labor intensive and therefore an expensive method. An alternative to surveying methods in the field is to use remotely sensed data acquired by, e.g. optical, radar, and laser sensors. In the present thesis, different remote sensing techniques for estimation of forest variables at stand level have been evaluated. All studies were performed in hemi-boreal coniferous dominated forest at a test site in southern Sweden (lat. 58°30’N, long. 13°40’E), enabling a detailed comparison. Remotely sensed data were related to field data using regression analysis. The root mean square error (RMSE) of the average stem volume using airborne laser scanning data, CARABAS-II radar data, aerial photo-interpretation, and multi-spectral optical satellite data was found to be 13%, 19%, 21-24%, and 24-32%, respectively. The analyses clearly demonstrate that airborne laser scanning is the single remote sensing technique of those investigated that gives the most accurate stem volume and tree height estimates at stand level. The estimates from laser scanning data are better than commonly achieved with subjective surveying methods in the field. The accuracy of forest variable estimation using aerial photo-interpretation of Z/I DMC images was found to be in agreement with the results using conventional film-based panchromatic photos. Hence, the results indicate that photo-interpretation of Z/I DMC images using a digital photogrammetric workstation could replace photo-interpretation of film-based photos using analog or analytical stereoplotters without loss of accuracy. Combining two or more data sources which are complementary gives the possibility of improving estimation accuracies. Here, two particularly successful approaches were found. A combination of multi-spectral optical satellite and tree height data improved the RMSE of stem volume estimation to 11-12%. Using a combination of multi-spectral optical satellite and CARABAS-II radar data improved the RMSE to about 15%. The application of the investigated remote sensing techniques in the forestry sector is restricted to the costs and the availability of remotely sensed data. In Sweden, airborne laser scanning data might be supplied by several companies operating in a pure commercial market. The National Land Survey has the mission of aerial photo mapping on a regular basis, but aerial photo mapping is also performed by commercial companies. For multi-spectral optical satellite and CARABAS-II radar data the governmental policy effects in practice what is offered to the users
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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