1,720,955 research outputs found
ASSESSING THE MEASUREMENT QUALITY OF UAV-BORNE LASER SCANNING IN STEEP AND SNOWCOVERED AREAS
No full textASSESSING THE MEASUREMENT QUALITY OF UAV-BORNE LASER SCANNING IN STEEP AND SNOWCOVERED AREASAvalanche monitoring in the Norwegian mountains has great potential for preventing catastrophes, such as avalanches affecting public roads, and for informing hikers about dangerous paths. Using an unmanned aerial vehicle (UAV) borne laser scanner to collect point clouds in real-time for snow depth change detection can potentially be used to monitor avalanche risks. The remaining issue is to determine the quality of the point cloud data in steep and snow-covered areas. This thesis suggests a protocol for assessing the quality of the point cloud data and investigates the impact of key flight parameters, speed and altitude above ground level, on measurement accuracy. Roof models are utilised as control planes to emulate steep areas and for easy extraction of collected point for further error analysis. The real-time positions of the control planes are derived and a plane is constructed to be compared with the collection of points above and below the roof models. The distances of the points to the control planes are used to investigate the median and median absolute deviation. Further, the absolute distance is used to find the arithmetic mean, standard deviation and root mean square error of the distances. Lastly, inliers and plane equations are constructed from the UAV-collected point clouds using random sample consensus (RANSAC) segmentation for comparison with the dimensions of the roof model. The angle, volume and mid-point difference is calculated between the two plane equations from the boundaries of the bounding boxes. These parameters provide key insight into reliability of the point cloud data. The comparison reveals tangible position data and the impacts of flight speed and altitude on accuracy. Although varied flight speed shows no notable change in the error measures, the amount of points collected is significantly effected by both speed and altitude. Notably, point coverage is concentrated near the top of the roof models. As a result, the model volume calculated from the RANSAC-constructed plane that most closely matches the volume under the roof model is only 50% of the expectation: 0.030minstead of 0.060 m. The RANSACderived plane equations are compared with the roof model planes. The investigations of the inliers shows more points are collected above the roof model planes than under. The standard deviations of the inliers are between 0.011mand 0.023 m, and the root mean square error is between 0.060 m and 0.019 m. The investigations reveal clear indications of UAVs reliability for monitoring steep and snow-covered areas, without support from reference points to correct the positions
ASSESSING THE MEASUREMENT QUALITY OF UAV-BORNE LASER SCANNING IN STEEP AND SNOW-COVERED AREAS
No full textOvervåkning av snøskred i de norske fjellene har stort potensial for å forebygge katastrofer, som for eksempel snøskred over offentlige veier, og for å informere skiløpere om farlige løyper. Bruk av en ubemannet flyvende enhet (UAV) med en laserskanner kan samle inn punkter i sanntid. Disse kan brukes for å oppdage endringer i snødybde som potensielt kan brukes til å overvåke snøskredrisiko. Et gjenværende problem er å bestemme kvaliteten til punktskydataene i bratte og snødekte områder. Denne oppgaven foreslår en metode for å vurdere kvaliteten på punktskydataene og undersøker påvirkningen av flyparametere, hastighet og høyde over bakkenivå, på målenøyaktigheten.
Takmodeller brukes som kontrollplan for å etterligne bratte områder og for å enkelt kunne finne ønskede punkter for ytterligere feilanalyse. Sanntidsposisjonene til kontrollplanene er målt og to plan er konstruert for å sammenligne punktene over og under takmodellene. Avstandene fra punktene til kontrollplanene brukes til å undersøke medianen og absolutt avvik i forhold til medianen. Videre brukes den absolutte avstanden til å finne det aritmetiske gjennomsnittet, standardavviket og kvadratisk gjennomsnittlig feil. Til slutt konstrueres planlikninger fra UAV-samlede punkter, som ligger i nærheten av dette planet. Dette gjøres ved hjelp av segmentering med \textit{random sample consensus} (RANSAC) og de konstruerte planene sammenlignes med takmodellene. Vinkelen, volumet og midtpunktforskjellen beregnes mellom de to planlikningene fra grenseverdiene til avgrensningsboksene. Disse parameterne gir nøkkelinnsikt i påliteligheten til punktskydataene.
Sammenligningen avslører håndgripelige posisjonsdata og de påvirkningene varierende flyhastighet og høyde har på nøyaktigheten. Selv om varierende flyhastighet ikke viser noen signifikant endring mellom nøyaktighetsmålingene, påvirkes antall samlede punkter betydelig av både hastighet og høyde. Det er observert at målte punkter er konsentrert nær toppen av takmodellene. Som et resultat av dette er volumet beregnet fra de RANSAC-konstruerte planene, betydelig lavere enn takmodellvolumet. Den konstruerte takmodellen fra RANSAC som samsvarer mest med volumet under takmodellen er bare 50% av forventningen: 0,030 m i stedet for 0,060 m. Undersøkelsene av inneliggende punkter viser at flere punkter samles over takmodellplanene enn under. Standardavviket til inneliggende punkter ligger mellom 0,011 m og 0,023 m, og den kvadratisk gjennomsnittlige feilen mellom 0,060 m og 0,019 m. Undersøkelsene avslører klare indikasjoner på pålitelighet ved bruk av UAV for overvåking av bratte og snødekte områder, uten støtte fra referansepunkter for å korrigere posisjonene.Avalanche monitoring in the Norwegian mountains has great potential for preventing catastrophes, such as avalanches affecting public roads, and for informing hikers about dangerous paths. Using an unmanned aerial vehicle (UAV) borne laser scanner to collect point clouds in real-time for snow depth change detection can potentially be used to monitor avalanche risks. The remaining issue is to determine the quality of the point cloud data in steep and snow-covered areas. This thesis suggests a protocol for assessing the quality of the point cloud data and investigates the impact of key flight parameters, speed and altitude above ground level, on measurement accuracy.
Roof models are utilised as control planes to emulate steep areas and for easy extraction of collected point for further error analysis. The real-time positions of the control planes are derived and a plane is constructed to be compared with the collection of points above and below the roof models. The distances of the points to the control planes are used to investigate the median and median absolute deviation. Further, the absolute distance is used to find the arithmetic mean, standard deviation and root mean square error of the distances. Lastly, inliers and plane equations are constructed from the UAV-collected point clouds using random sample consensus (RANSAC) segmentation for comparison with the dimensions of the roof model. The angle, volume and mid-point difference is calculated between the two plane equations from the boundaries of the bounding boxes. These parameters provide key insight into reliability of the point cloud data.
The comparison reveals tangible position data and the impacts of flight speed and altitude on accuracy. Although varied flight speed shows no notable change in the error measures, the amount of points collected is significantly effected by both speed and altitude. Notably, point coverage is concentrated near the top of the roof models. As a result, the model volume calculated from the RANSAC-constructed plane that most closely matches the volume under the roof model is only 50% of the expectation: 0.030 m instead of 0.060 m. The RANSAC-derived plane equations are compared with the roof model planes. The investigations of the inliers shows more points are collected above the roof model planes than under. The standard deviations of the inliers are between 0.011 m and 0.023 m, and the root mean square error is between 0.060 m and 0.019 m. The investigations reveal clear indications of UAVs reliability for monitoring steep and snow-covered areas, without support from reference points to correct the positions
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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