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Telerilevamento di rocce granitoidi in ambiente desertico (Anti - Atlante Orientale - Marocco) ed alpino (Himalaya - Nepal Occidentale): elaborazione immagini ASTER e spettroscopia
Get PDFThe aim of this research is to characterize the spectral signatures of granitoid rocks in visible and infrared wavelengths regions and find effective methodologies to discern and map granitoid plutons using ASTER (Advanced Spaceborne Thermal Emission and Reflectance Radiometer) multispectral satellite images in different environmental contexts. Despite satellite remote sensing analysis has been extensively used for geological mapping, it is not considered readily applicable to the mapping of igneous terrains, where lithological contacts are less predictable. For this reason several plutons in two different geological contexts have been taken into account: i) Anti-Atlas - Morocco Edyacarian and Cryogenian plutons (Eastern Sagrho) and ii) Himalaya - Tertiary plutons (Dolpo).
Particular attention has been given to the pre-processing of the ASTER L1A and L1B images. Level-1B data have been generated performing the radiometric calibration and geometric resampling of Level-1A products. In this way radiance at sensor (W/m2/sr/Î1⁄4m) is obtained from the DN (Digital Number). Subsequently, ASTER images have been corrected for the crosstalk effect, resampled at the same spatial resolution (15m/pixel), georeferenced and orthorectified. Finally, radiance at sensor values have been converted to ground reflectance applying atmospheric correction and, where necessary, the topographic effects on spectra has been reduced performing a topographic normalization.
In order to compare ASTER spectra with the minerals and rocks ones, ASTER Spectral Library version 2.0 (Baldridge et al., 2009) have been considered. This library includes contributions from the Jet Propulsion Laboratory (JPL), Johns Hopkins University (JHU) and the United States Geological Survey (USGS) (Christensen et al., 2000, Clark et al., 1993, 2007). In addition, forty-five samples of granitoid rocks collected in the field, were analyzed in the VIS/SWIR spectral range at the DEI (Department of Information Engineering - Università di Padova) using the VARIAN-CARY5000R spectrophotometer in a wavelength range spanning from 0.35Âμm to 2.5Âμm at a 1nm sampling step. High-resolution spectral signatures were resampled simulating the ASTER bands filter. This transformation drastically decrease the discerning capability of spectral signatures since the 2150 laboratory "bands" are reduced to the 9 bands obtained by the ASTER filters in the VIS/SWIR range.
The remote sensing elaboration in Morocco was challenging in discriminating Ediacarian granitoid bodies, that are characterized by very similar compositions and a widespread desert varnish coating. Using false color composites, band ratios, spectral angle mapper (SAM) and supervised maximum-likelihood (MLL) classifications on ASTER bands, we were able to discriminate and map four calc-alkaline plutons. The analytical comparison of ASTER TIR (Thermal Infrared Region) and VNIR/SWIR (Visible Near Infra Red Region, Short Wave Infrared Region) data has demonstrated that the latter are very effective in the distinction of granitoids, although with very similar silica content. This because secondary effects like hydrothermal and surface alterations which may depend respectively on the magmatic evolution and on the texture and modal composition of the plutonic body, can be quite easily recognized.
The remote sensing elaborations in Himalayan case study, point out that detailed lithological discrimination of heavily vegetated and topographically rough areas, requires advanced digital image processing techniques. A good approach consists on masking no -"bedrock" pixels through a classification based filter which excludes water, snow, vegetation and clouds. Subsequently we were able to cluster "rocky" pixel reflectance values into a few end-members, each with a specific mean spectral signature. Indeed, these "rocky" pixels have shown signatures constituted by a non-linear mixing of rocks and lichens. In particular, granitoid rocks of the Higher Himalayan Granitoid form an acid substrate influencing the distribution of acidophilic lichens species which can be diagnostic of such rocks. Consequently, the effect of these lichens on rock spectra along with muscovite absorption bands can be used as a proxy for the presence of leucogranitic rocks in mid latitude alpine environment. The image analysis were carried out on SWIR wavelengths using false color composites of band ratios and PCAs (Principal Component Analysis) studied under the light of this new finding. In this way the image analysis provided the detection and the geological map of a new 110 km2 granitoid body (Buraburi Granite-BG) in the Dolpo region.
Results point out that the pre-processing and processing steps necessary to geological remote sensing application must be chosen in function of the specific scene characteristics (season and the environments). Moreover, has been highlighted the important role of the indirect proxies, such as desert varnish and acidophilic lichens, in the granitoid rocks spectral discrimination, based on satellite signature.La presente ricerca ha lo scopo di sperimentare tecniche di telerilevamento multispettrale atte alla discriminazione e mappatura di plutoni granitici e caratterizzare la risposta spettrale di rocce granitoidi nelle lunghezze d'onda del visibile, vicino e medio infrarosso e infrarosso termico.
Nonostante il telerilevamento satellitare sia stato ampiamente applicato alla geologia, le potenzialità del sensore ASTER (Advanced Spaceborne Thermal Emission and Reflectance Radiometer) non sono state mai applicate alla cartografia di corpi granitici. In questo lavoro si sono così presi in considerazione numerosi plutoni in due diversi contesti geologici ed ambientali: i) plutoni di età Ediacariana e Cryogeniana presenti nell'Anti-Atlas Orientale (Sagrho orientale - Marocco) e ii) plutoni Terziari dell'Himalaya meridionale (Dolpo - Nepal occidentale).
Nelle analisi delle immagini ASTER si è prestata una particolare attenzione alle fasi di pre-processing, dove si sono applicate le calibrazioni e correzioni radiometriche e geometriche necessarie ad ottenere un dato valido, sia dal punto di vista spettrale che spaziale.. I dati di ASTER di livello 1a, attraverso la calibrazione radiometrica, sono stati così trasformati da DN (Digital Number) in radianza al sensore (W/m2/sr/Î1⁄4m), ottenendo un dato di livello 1b. Questo è quindi stato corrette per l'effetto di crosstalk, ricampionato alla stessa risoluzione spaziale (15m/pixel), georeferenziato e ortoretificato. Infine, attraverso l'applicazione della correzione atmosferica, i valori di radianza al sensore sono stati convertiti in valori di riflettanza al suolo. Nell'immagine dell'area Himalayana, caratterizzata da un'alta energia di rilievo, si è inoltre applicata la correzione topografica.
Le firme spettrali ricavate dall'immagine satellitare sono state confrontate con quelle ad alta risoluzione di minerali, misurate in laboratorio e presenti nella libreria spettrale ASTER Spectral Library v.2.0 (Baldridge et al., 2009). A queste firme si sono aggiunte quelle di minerali e rocce di oltre 45 campioni di granitoidi raccolti nelle aree di studio ed analizzati con lo spettrofotometro VARIAN-CARY5000R nell'intervallo di lunghezze d'onda tra 0.35Âμm e 2.5Âμm (visibile -medio infrarosso) con una risoluzione di 1nm. Le firme spettrali ad alta risoluzione (circa 2150 bande) sono state così ricampionate secondo la risoluzione delle 9 bande ASTER.
Le analisi di telerilevamento dell'area marocchina hanno consentito la distinzione di quattro plutoni calc-alcalini di età Ediacariana, caratterizzati da una composizione molto simile e da una diffusa copertura di vernice del deserto sulla superficie degli affioramenti. La discriminazione di queste rocce granitoidi è stata effettuata grazie allo studio delle immagini in scala di grigi e combinazioni RGB a falsi colori di bande ASTER, rapporti tra bande ASTER e classificazioni di tipo supervised, quali maximum-likelihood (MLL) e spectral angle mapper (SAM).
I dati dei sistemi ASTER VNIR/SWIR (Visible Near Infra Red Region, Short Wave Infrared Region) si sono comunque mostrati più efficaci di quelli del sistema TIR (Thermal Infrared Region), nella discriminazione delle rocce considerate. Questo è principalmente dovuto alla presenza di alterazioni idrotermali e superficiali, caratterizzate da assorbimenti diagnostici nella regione VNIR-SWIR, che di fatto dipendono dall'evoluzione magmatica, dalla tessitura e dalla composizione del litotipo indagato.
Le analisi di telerilevamento dell'area Himalayana, caratterizzata dalla presenza di vegetazione, nuvole, neve e ghiaccio ha richiesto l'utilizzo di tecniche più complesse di quelle utilizzate nell'area Marocchina, caratterizzata da una buona esposizione degli affioramenti. Il mascheramento dei pixel non rocciosi si è così mostrato un buon approccio in aree con clima alpino. Le firme spettrali da satellite degli affioramenti leucogranitici analizzati, si mostrano influenzate dalla presenza di un'associazione di roccia e licheni. Poichè le rocce granitiche sviluppano substrati acidi, la presenza di specie licheniche acidofiliche è diagnostica della composizione della roccia sottostante. La presenza congiunta di assorbimenti caratteristici dei licheni acidofilici e della muscovite negli spettri da satellite possono quindi essere interpretati come proxy della presenza di rocce leucogranitiche. Si sono quindi analizzate le immagini in scala di grigi e composizioni a fasi colori di rapporti tra bande, assorbimenti relativi di banda e componenti principali, mirate ad enfatizzare gli assorbimenti di licheni e muscovite. In questo modo, le elaborazioni di telerilevamento, unite alle analisi spettrali hanno portato alla scoperta di un corpo granitico di 110 km2 (Buraburi Granite-BG) nella regione del Dolpo (Nepal occidentale).
I risultati portano a concludere che le fasi di pre-processing e processing mirate alle applicazioni geologiche del telerilevamento, devono essere scelte e pesate in base agli specifici contesti ambientali e stagionali. Infine si è dimostrata l'importanza dei proxies quali licheni acidofilici e vernice del deserto, nel riconoscimento indiretto, da satellite, di rocce granitiche
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
Interpretation and processing of ASTER data for geological mapping and granitoids detection in the Saghro massif (eastern Anti-Atlas, Morocco)
No full textSatellite remote sensing analysis is extensively used for geological mapping in arid regions. However, it is not considered readily applicable to the mapping of metamorphic
and igneous terrains, where lithological contacts are less predictable. In this work, ASTER (Advanced Spaceborne Thermal Emission and Refl ection Radiometer) data were used to clarify the geological framework of the Precambrian basement in the Saghro massif (eastern Anti-Atlas, Morocco). The Saghro basement is composed of low-grade
metasedimentary sequences of the Saghro Group (Cryogenian), intruded by calcalkaline plutons of late Cryogenian age. These rocks are unconformably covered by volcanic to volcaniclastic series of Ediacaran age that
are broadly coeval with granitoid plutons. All of these units are cut by a complex network of faults associated with hydrothermal fluid flows, which developed during and shortly
after the emplacement of the volcanic rocks. The geological mapping of the Precambrian units was challenging in particular for the Ediacaran granitoid bodies, because they are characterized by very similar compositions and a widespread desert varnish coating. For this reason, a two-stage approach has been adopted. In the first step, false color composites, band ratios, and principal components analyses on visible and near infrared (VNIR) and shortwave infrared (SWIR) bands were chosen and interpreted on the basis of the field and petrographic knowledge of the lithologies in order to detect major lithological contacts and mineralized faults. In the second step, a major effort was dedicated to the detection of granitoid plutons using both thermal infrared (TIR) and VNIR/SWIR data. The ASTER TIR bands were used to evaluate Reststrahlen and Christiansen effects in the granitoid rocks spectra, whereas VNIR/SWIR false color composite and ratio images were chosen directly on the basis of the granitoid spectra (derived from both spectrophotometric analyses of samples and selected sites in the ASTER image). Finally, spectral angle mapper (SAM)
and supervised maximum-likelihood classifications (MLL) were carried out on VNIR/SWIR data, mainly to evaluate their potential for discriminating granitoid rocks.
The results have further demonstrated the value of ASTER data for geological mapping of basement units, particularly if the processing has been based on a detailed knowledge
of the rock mineral assemblages. In addition, the analytical comparison of ASTER TIR and VNIR/SWIR data has demonstrated that the latter are very effective in the distinction of granitoids with very similar silica content, because they can be recognized by secondary effects related to their hydrothermal and surface alterations (K-feldspar
kaolinitization, plagioclase saussiritization, substitution of mafic minerals with oxides, inhomogeneous desert varnish coating, and clay/oxide proportions)
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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