1,720,965 research outputs found
Normalized Burn Ratio Plus (NBR+): A New Index for Sentinel-2 Imagery
Full text linkThe monitoring of burned areas can easily be performed using satellite multispectral images: several indices are available in the literature for highlighting the differences between healthy vegetation areas and burned areas, in consideration of their different signatures. However, these indices may have limitations determined, for example, by the presence of clouds or water bodies that produce false alarms. To avoid these inaccuracies and optimize the results, this work proposes a new index for detecting burned areas named Normalized Burn Ratio Plus (NBR+), based on the involvement of Senti-nel-2 bands. The efficiency of this index is verified by comparing it with five other existing indices, all applied on an area with a surface of about 500 km2 and covering the north-eastern part of Sicily (Italy). To achieve this aim, both a uni-temporal approach (single date image) and a bi-temporal approach (two date images) are adopted. The maximum likelihood classifier (MLC) is applied to each resulting index map to define the threshold separating burned pixels from non-burned ones. To evaluate the efficiency of the indices, confusion matrices are constructed and compared with each other. The NBR+ shows excellent results, especially because it excludes a large part of the areas incorrectly classified as burned by other indices, despite being clouds or water bodies
A Proposal for Automatic Coastline Extraction from Landsat 8 OLI Images Combining Modified Optimum Index Factor (MOIF) and K-Means
No full textThe coastal environment is a natural and economic resource of extraordinary value, but it is constantly modifying and susceptible to climate change, human activities and natural hazards. Remote sensing techniques have proved to be excellent for coastal area monitoring, but the main issue is to detect the borderline between water bodies (ocean, sea, lake or river) and land. This research aims to define a rapid and accurate methodological approach, based on the k-means algorithm, to classify the remotely sensed images in an unsupervised way to distinguish water body pixels and detect coastline. Landsat 8 Operational Land Imager (OLI) multispectral satellite images were considered. The proposal requires applying the k-means algorithm only to the most appropriate multispectral bands, rather than using the entire dataset. In fact, by using only suitable bands to detect the differences between water and no-water (vegetation and bare soil), more accurate results were obtained. For this scope, a new index based on the optimum index factor (OIF) was applied to identify the three best-performing bands for the purpose. The direct comparison between the automatically extracted coastline and the manually digitized one was used to evaluate the product accuracy. The results were very satisfactory and the combination involving bands B2 (blue), B5 (near infrared), and B6 (short-wave infrared-1) provided the best performance
Horizontal Accuracy Tests on Google Satellite Images Over Naples Added in QGIS
No full textThe possibility of view Google satellite images in Geographic Information System (GIS) provides an important source of information for free to support applications regarding smart cities. In fact, Google makes available, practically for every place on Earth, updated and high-resolution images: it is necessary to ascertain that the data accuracy is compatible with the application you want to create. Consequently, it becomes necessary to verify that the coordinates of objects easily identifiable in the images are sufficiently accurate for the purpose. This article aims to verify the horizontal positional accuracy of the Google satellite images in the municipality of Naples (Italy). For this purpose, the 1:1,000 scale maps georeferenced in the UTM WGS84 system, zone 33 North are used. The satellite images, georeferenced in the WGS84 system and in the WEB Mercator representation, are also reported in the same system and projection as the maps. Due to the imperfect overlap between the layers, the deviations are measured in some points that are easily identifiable both on the maps and the satellite images. As found with the use of 45 check points, the deviations have a root mean square error (RMSE) of 1.594 m highlighting a wide range of possible applications
Water Body Detection in Sentinel-2 Satellite Images to Integrate GIS Data for Rome Smart City
No full textThe water bodies (rivers, lakes, seas and oceans) often constitute founding elements of the cities landscape, so a monitoring action to preserve their environmental value is undoubtedly necessary. Remotely sensed images can offer
quick, effective and economic support for monitoring water bodies, providing their position, form, extension, consistence and state of health. This article aims to highlight how Normalized Difference Water Index (NDWI) applied to Sentinel-2 satellite images allows to monitor water bodies and detect the variations over time connected to disturbing causes due to climate change and phenomena such as drought and floods. The city of Rome is taken into consideration particularly significant for the presence of both an important river such as the Tiber (third in Italy by length), and for a long stretch of coast on the Tyrrhenian Sea. The results demonstrate that a fast procedure is possible for water body detection in Rome to integrate Geographic Information System (GIS) data and support monitoring plan.
In fact, NDWI applied in QGIS allows to obtain a map of the area which, suitably classified using maximum likelihood algorithm, produces an identification of water bodies with high accuracy (user, producer and overall accuracy values
are all greater than 98%)
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
Soil water balance and irrigation strategies in an agricultural district of Southern Italy
Full text linkAppropriate 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
Delineation of site-specific management zones using geostatistics and fuzzy clustering analysis.
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