1,720,968 research outputs found
L’ALTERAZIONE DEI DEFLUSSI IDRICI SUPERFICIALI DA PARTE DEI SEGMENTI VIARI E DEI SENTIERI: L’EFFICACIA DELLA TOPOGRAFIA AD ALTA RISOLUZIONE
No full textIn ambiente montano la viabilità silvo-pastorale produce effetti significativi sugli assetti
idro-morfologici del territorio con conseguenze sui processi erosivi e sulla dinamica dei
sedimenti. L’alterazione dei deflussi idrici da parte dei segmenti viari ha come
potenziale conseguenza l’innesco di erosioni superficiali e di fenomeni di dissesto, sia
alla scala del singolo segmento stradale che a quella di versante e di bacino, con
conseguente incremento del livello di pericolosità a cui vengono esposti eventuali
insediamenti, infrastrutture ed attività antropiche. A scala diversa e con un diverso
livello di intensità lo stesso problema può verificarsi anche per la rete di sentieri ad
alta percorrenza in aree interessate da un significativo flusso turistico quali parchi e
riserve. È quindi di grande rilevanza poter individuare le aree soggette, o
potenzialmente soggette, a tali processi di instabilità ed intervenire o per mitigare il
problema o in modo preventivo per evitarne il manifestarsi in futuro.
Questa nota propone un metodo speditivo e oggettivo per l’individuazione delle aree
potenzialmente soggette a fenomeni di dissesto dovuti all’azione idroerosiva derivante
dall’alterazione dei deflussi idrici da parte di strade forestali o sentieri. L’analisi è
condotta utilizzando la topografia ad alta risoluzione con modelli digitali del terreno
(DTM) derivati da rilievo LiDAR ad una risoluzione di cella ≤ 1 m. La metodologia
proposta consiste nel calcolo di un indicatore di alterazione del deflusso mediante la
comparazione dell’area drenata ricavata da DTM filtrato su finestra (kernel) e area
drenata ricavata da DTM originale.
I risultati hanno portato alle seguenti osservazioni: i) le alterazioni dei deflussi più
evidenti hanno riguardato quelle porzioni di territorio interessate da strade per le quali
sono stati riscontrati in campo evidenti fenomeni di dissesto, ii) è stato possibile
evidenziare, là dove era possibile impiegare un DTM di 0.5 m, erosioni superficiali
dovute ad alterazioni di deflusso su sentieri di trekking.
Il metodo proposto permette di ricavare in modo totalmente oggettivo, su ampie
porzioni di territorio montano, un indicatore capace di riconoscere le aree potenzialmente soggette a fenomeni di dissesto derivati dall’azione antropica.. Il
metodo sviluppato si pone come una prima e speditiva analisi,suscettibile di affinamenti
in base ad applicazioni di tipo modellistico e verifiche in campo, ma in se utilizzabile
per programmare interventi utili alla mitigazione degli effetti indesiderati della
presenza delle infrastrutture viarie
Automatic recognition of road and pathway induced slope instabilities by high resolution topography
No full textComparative analysis of terrestrial laser scanner and photogrammetry for the mass balance calculation of Montasio Occidentale Glacier
No full textRecognition of surface flow processes influenced by roads and trails in mountain areas using high-resolution topography
Full text linkRoad networks in mountainous forest landscapes have the potential to increase the susceptibility to erosion and shallow landsliding. The same issue is observed also for minor trail networks, with evidences of surface erosion due to surface flow redistribution. This could be a problem in regions such as the Italian Alps where forestry and tourist activities are a relevant part of the local economy. This is just one among the several effects of modern anthropogenic forcing: it is now well accepted by the scientific community that we are living in a new era where human activities may leave a significant signature on the Earth, by altering its morphology, and significantly affecting the related surface processes. In this work, we proposed a methodology for the automatic recognition of roads and trails induced flow direction changes. The algorithm is based on the calculation of the drainage area variation in the presence, or in the absence of anthropic features such as roads and trails on hillslopes. To simulate the absence of alteration, the surface was smoothed considering moving windows of varying size. In the analysis, we used a 1 and 0.5 m Airborne Laser Swath Mapping technology (ALSM), using LiDAR (Light Detection And Ranging), and 0.2 m Terrestrial Laser Scanner (TLS) derived Digital Terrain Models (DTMs). The aim of the work is to underline the effectiveness of the proposed method based on high resolution topography in the detailed recognition of surface flow direction alteration due to roads, but also trail networks. We propose an automatic method to map at a large scale such alterations, also in areas where it is difficult to recognize them without a trail network surveyed in the field. This methodology could be considered as a support for modeling (i.e., terrain stability and erosion models), and it can be used to interactively assist the design of new infrastructure to reduce their effects on surface instabilities. The reported methodology could also have a role in risk management and environmental planning for mountain areas where tourism and the related economic activities are critical, and where also trails deserve attention due to induced slope instabilities
Terrestrial Laser Scanner survey of a small headwater basin in the Dolomites
No full textAirborne LIDAR technology has led to a dramatic increase in terrain information. LiDAR-derived high-resolution
Digital Terrain Models (DTMs) are now widely available, and have opened avenues for hydrologic and geomorphologic studies (Tarolli et al., 2009). In general all the main surface processes signatures are rightly recognized
using a DTM grid cell size of 1 m or 0.5 m. Having said that some sub-meter alterations of surface morphology
in the high-altitude headwater catchments, still are not recognized using this resolution. These are such signatures
related to the hillslope flow directions changing due to trail path and grazing activity. The possibility to detect
in detail such signatures means also to find a way to better understand and mapping the surface and shallow
landsliding susceptibility in alpine regions. Terrestrial Laser Scanner (TLS) was proven to be a useful tool for
detailed field survey. The acquired elevation data with TLS allows to derive a centimeters high quality DTMs. In
this work we present an example of such application. A TLS survey was carried out in a couple of day, in October
2011, in the Rio Cordon catchment, in Dolomiti Regions (central Italian Alps). The Rio Cordon catchment has
a surface of 5 km2, the survey was focused on the portion where the main erosion and landsliding processes
occur, corresponding at about half of total basin surface. The aim of this work is to describe the issues related
to a TLS survey in a wilderness high altitude region, and test the capability of centimeter DTMs in recognizing
the signatures related to hillslope flow directions changing. The method can be considered as a useful tool to
interactively assist the interpreter/user on the task of soil erosion and shallow landslide hazard mapping
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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