1,720,970 research outputs found
River morphology monitoring using multitemporal sar data: Preliminary results
No full textIn this paper, we test the capability of satellite synthetic aperture radar (SAR) images to enhance the monitoring of river geomorphological processes. The proposed approach exploits the recently introduced Level-1a products. These products are bi-temporal RGB composites in which the association color-object, being physical-based, is stable whatever the scene is considered. This favors the detection of temporary rivers’ characteristics for classification purposes in a change-detection environment. The case study was implemented on the Orco river (northwest Italy), where a set of 39 COSMO-SkyMed SAR stripmap images acquired from October 2008 to November 2014 was used to monitor channel planform changes. This preliminary study is devoted to assess the suitability of Level-1a images for geomorphologist, with particular reference to the detection of phenomena of interest in river monitoring. This is prior for semi-automatic or automatic classification activities
Potential and limitations of high resolution multitemporal sar images in river morphology
No full textIn this study we test the capability of satellite synthetic aperture radar (SAR) images to enrich the monitoring of
river geomorphological processes. A case study on the Italian River Orco is presented; a set of 100 COSMOSkyMed stripmap images (from October 2008 to December 2016) from Italian Space Agency was employed.
All the data, acquired with medium look angle (almost 30◦) and HH polarization for increasing the land-water
contrast, were processed in order to calibrate, register and reduce the speckle effect. Moreover, the optimal
weighting multi-temporal De Grandi filter was adopted to allow an effective extraction of the water surfaces
contour. This method was applied to extract water contours over the entire historical series of SAR datasets
available. Thanks to the generated information we were able to monitor the lateral dynamic of the water channels
and infer on the relations between low or peak flow and river morphology.
Multi-temporal SAR images were compared to orthophotos and in situ measurements (performed at the
same time of a SAR acquisition) in terms of river features extraction (e.g. active channel, vegetated islands) and
measurements of morphometric parameters (e.g. reach length, channel width, curvature and sinuosity). Results
of this comparison highlighted the potential offered by the use of SAR technology, with some limitations. In
particular, good performances were reached by the extraction of the active channel and vegetated island compared
to the ones obtained using the orthophotos. On the other hand, some issues were encountered in extracting water
surfaces where riffles exhibit surface waves having heights greater than the wavelength of the electromagnetic
signal of SAR, which causes a low land-water contrast. Hence, given the high spatial (3 m) and temporal resolution
(15 days) of SAR images and the all-weather all-time acquisition conditions, a significant enhancement in the
river management capabilities is possible, in particular regarding the assessment of hydro-morphological river
quality, as strongly suggested by European Commission’s Water Framework Directive (2000/60/EC
SAR remote sensing of river morphodynamic on a monthly basis
No full textSatellite remote sensed data provide the opportunity of
observing rivers with high resolution in space and time
and covering wide areas. For this reason, such data have
been widely used to monitor river morphological
changes in time (Marcus and Fonstad, 2010). In this
study we propose the exploitation of satellite synthetic
aperture radar (SAR) data. Although SAR data have
been so far poorly used for river observation they have
significant advantages over more widely used data such
as for example optical one: cloud cover do not influence
earth surface observation, the spatial resolution is very
high (up to 1m) and the time resolution is also very high
(about 15 days). In this study we retrieved from a multitemporal SAR dataset the surface covered by water, we
tested the results against orthophotos and in situ
measurements and observed the river morphological
change in a time interval of 8 years with an average
frequency of about one month
Advanced Technologies for Satellite Monitoring of Water Resources
No full textExploitation of synthetic aperture radar satellite data. Monitoring of surface water resources with high resolution in time and space. Low-cost technic for freshwater monitoring. Appropriate technology for developing countries. Retrieval of river features: active channels, sediment bars and wet channels
Monitoring river morphological changes using high resolution multitemporal sar images: a case study on orco river, italy
No full text
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
- …
