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Difference between time-of-flight and phase-shift laser scanners in tree measurements
Get PDFMaalaserkeilauksen (Terrestrial Laser Scanning, TLS) on viime aikoina osoitettu soveltuvan hyvin puustoparametrien ratkaisemiseen. TLS on tarjonnut useassa tutkimuksessa lupaavia tuloksia esimerkiksi runkojen havaitsemisessa, rinnankorkeuden läpimitan (Diameter at Breast Height, DBH) mittaamisessa, rungon laadun ja muutoksen mittaamisessa sekä puunkorkeuden, puutilavuuden ja biomassan arvioinnissa. Vaikka TLS:n soveltuvuus metsämit-tauksissa on lupaava, on sen suurena ongelmana latvusten läpäisemättömyys. Monet edellä mainituista tutkimuksista on tehty vaihe-erokeilaimella. Osa on tehty pulssikeilaimella, mutta pulssikeilaimen ja vaihe-erokeilaimen välisiä eroja puustomittauksissa ei tiettävästi ole tutkittu. Jotta TLS-laitteistoa voidaan jatkossa hyödyntää laajemmin metsämittauksissa, tulee tietää, kumpi mittaustekniikka siihen parhaiten soveltuu.
Tässä työssä verrattiin kahden keilausmenetelmän, pulssimittauksen (Time of Flight, ToF) ja vaihe-eromittauksen (Phase Shift, PS), eroja puustomittauksissa keilaamalla ja pistepilvistä mittaamalla kuudella koealalla. Tutkimuksessa suoritettiin puustomittaukset keilainkohtaisesti jokaiselle koealalle niin yksittäisen (Single-Scan, SS) kuin useamman (Multi-Scan, MS) keilauksen tapauksessa. Puustomittaukset tehtiin sekä manuaalisesti että automaattisesti. Manuaalimittauksissa mitattiin aineistosta havaittujen puunrunkojen lukumäärä, kokonaisten puiden lukumäärä sekä havaitun puun rungon ylin mitattavissa oleva läpimitta. Automaatti-mittaukset suoritettiin tähän tarkoitukseen kehitetyllä algoritmilla. Algoritmi etsi aineistosta kaikki mitattavissa olleet puunrungot, rakensi näkyvänä olleiden puunrunkojen perusteella runkokäyriä ja estimoi puiden korkeudet runkokäyrän perusteella.
Tulosten mukaan pulssikeilaimen läpäisykyky on parempi kuin vaihe-erokeilaimen läpäisykyky, kun on kyse puustomittauksista. Jokainen läpäisykykyä indikoiva tulos oli pulssikeilaimella parempi niin SS- kuin MS-mittauksissa. Läpäisykyvyn erot olivat tulosten mukaan kuitenkin merkittävästi suuremmat SS-mittauksissa. Kun verrattiin pulssikeilaimella saatuja tuloksia vaihe-erokeilaimiin SS-tapauksessa, paranivat tulokset keskimäärin seuraavanlaisesti: kokonaisia puita saatiin 52 % enemmän näkyviin, puun runkoja saatiin 10 % enemmän näkyviin ja puunrunkojen läpimitat saatiin mitattua 13 % korkeammalta. Vastaavat luvut MS-tapauksessa olivat 37, 4 ja 10 %. Algoritmin avulla saatiin SS-tapauksessa rungon läpimitta mitattua pulssikeilaimella keskimäärin 6 % korkeammalta. Puita havaittiin samassa mittausasetelmassa keskimäärin noin 16 % enemmän pulssikeilaimen hyväksi. Vastaavat luvut MS-tapauksessa olivat noin 3 ja 7 %.Terrestrial laser scanning (TLS) has been proved to be a promising technique in tree measurements. In many studies TLS has been proved to provide some promising results in evaluating tree attributes such as number of stems, stem density, diameter at breast height (DBH), tree height, stem curves, stem volume, biomass, stem quality and change of stems. However, TLS measurements face the problem with the bad penetration through branches and leaves. Many previously mentioned studies have been done by using phase-shift (PS) laser scanners (LS). No studies about the difference between PS-scanners and time-of-flight (ToF) scanners in forest inventory could be found. In order to use TLS widely in forest measurements, the differences between TLS techniques have to be known.
In this study, the differences between PS-technique and ToF-technique have been compared by scanning and analysing 6 test plots. Tree attributes were measured from each laser scan-ner in Single-Scan (SS) and Multi-Scan (MS) mode. The LS data was analysed manually and automatically. In the manual measurements the number of complete trees, number of stems and the height of the highest measurable point of the stem were measured. In automatic measurements the algorithm locates each stem, creates a stem curve and estimates a height for a tree.
The results indicate a better penetration for the ToF-scanner when it is compared to the PS-scanner when it comes to tree measurements. In both measuring modes (SS and MS), each result indicated a better penetration for the ToF-scanner. The biggest difference between ToF and PS was in the SS-mode. The following percentages show how much the ToF results differed from the PS results in the SS-mode: 52 % in finding complete trees, 10 % in finding stems and 13 % in measuring the highest point of the measurable diameter. The corresponding results in the MS-mode were 37 %, 4 % and 10 %. In the automatic measurements, the highest point of the measurable diameter was 6 % better in ToF-data in the SS-mode. In the same mode algorithm found from ToF-data 16 % more stems compared to PS-data. Corresponding results for MS-mode were 3 and 7 %
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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