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Page 200 of 977 Results 1991 - 2000 of 9762

Anselme Muzirafuti, Antonio Crupi, Stefania Lanza, Giovanni Barreca, Giovanni Randazzo
Shallow water bathymetry by satellite image: a case study on the coast of San Vito Lo Capo Peninsula, Northwestern Sicily, Italy

Mapping coastal areas and shallow water depth has become an interesting topic for hydrographers and scientists. Many techniques using traditional methods have been used to map and study seabed evolutions of these areas. However, ships, vessels and aircrafts used for bathymetric surveys in shallow water present some limitations, especially their inability to map hard-to-reach areas and very near shoreline waters. In addition, the cost and human resources deployed to conduct these surveys make them very expensive, even for small projects. In this paper we present a cost-effective tool and a practical method for bathymetric studies of shallow water using multispectral satellite images. We applied the Satellite-derived bathymetry (SDB) method on the coast of San Vito Lo Capo with a Geoeye-1 satellite image, using available field data for calibration and vertical referencing. The results show bathymetric information for a depth of 10 m with R2=0.753, contributing to the management of ports, maritime transport and the coastal environment in general.

Lorenzo Rossi, Irene Mammi, Filippo Pelliccia
UAV multispectral images for bathymetry estimation

Bathymetric data are commonly used for coastal erosion monitoring and engineering projects. Multispectral satellite imagery is nowadays commonly applied to derive bathymetry with different literature algorithms. The present study shows the results of a Unmanned Aerial Vehicle (UAV), also known as drone, derived bathymetry (UDB) equipped with a multispectral camera acquiring in the same WorldView-2 sensors spectral bands. An hydrographic Multibeam Echosounder (MbEs) survey was performed in the same period in order to validate the method accuracy. The study area is approximately 0.5 km2 and located in Tuscany (Italy). Because of the high percentage of water in the images, an alternative method was also implemented for producing a georeferenced orthophoto mosaic. Multispectral images were processed to retrieve bathymetric data with Stumpf and Lyzenga algorithms. Results show the possibility to produce accurate UDB in shallow waters with low operational costs and the capability to obtain a full sea-floor coverage where MbEs is usually unable to work properly.

Wehde H., Thomsen L., Pfannkuche O., Albiez J., Flogel S., Godo O.R., Torkelsen T., Valencia J., Rodriguez E., Lopez V., Marini S., Grimsbo E., Zhang G., Aguzzi J.
A flexible autonomous bottom resident infrastructure for bentho-pelagic monitoring

This paper presents the ecology and policy basis as well as the technology solution for a Martera funded project (ARIM). The project develops platforms for bentho-pelagic monitoring using an arrangement of crawler and stationary platforms. A combination of visual and acoustic sensing along with standard oceanographic sensors supports advanced and continues spatial-temporal monitoring. Just as important is the automatic processing techniques under development that will allow habitat and species (or categories of species) to be automatically recognized and reported during the mission and thus support science and monitoring services without backing from expensive ship time. First version develops autonomy under controlled conditions with a tethered crawler exploring the neighbourhood of a cabled stationary instrumented garage. Our vision is that fuel cell technology will enable us to use the system for selfsustained long-term autonomous operations for science as well as for industry purposes.

Nikolla Gjeci, Shashank Govindaraj, Sander Coene, Alexandru But, Ennio Ottaviani
Transmission of classified and varying quality underwater maps over constrained networks

Autonomous underwater mapping operations are limited by onboard energy constraints in AUVs. The ENDURUNS project proposes to use fuel cells technologies to provide extended duration of AUV mapping operations. This type of mission generates large quantities of multi-beam sonar data available onboard at remote maritime locations. Satellite links can provide connectivity from remote control centers to these unmanned assets, but have limited bandwidth to transfer unprocessed data. This paper describes onboard semantic classification of raw sensor data using deep learning for a compressed representation of data for operators to analyze and selectively demand higher resolution data for specific areas of interest from large data sets. This is aimed at providing access to downstream end users and stakeholders with the required data within the constraints of communication technologies with minimal operational delay.

Emanuela Fanelli, Jacopo Aguzzi, Raffaella Casotti, Fabio Conversano, Domenico D Alelio, Daniele Iudicone, Simone Marini, Sergio Stefanni
NEREA, the Naples Ecological REsearch for Augmented observatories: Towards an end-to-end transdisciplinary approach for the study of marine ecosystems

Here we present the concept of NEREA, the Naples Ecological REsearch for Augmented observatories, an integrated observatory with a modular, adaptive structure, characterised by two main modules, NEREA-mob and NEREA-fix. NEREA-mob is conceived as monthly sampling at a coastal station in the Gulf of Naples where the whole water column is sampled for end-to-end (from microbes to fish) biological parameters coupling traditional with omic approaches (metagenomics, metatranscriptomics and metabolomics). NEREA-fix will be deployed in 2020 in the Dohrn canyon at ca. 600 m, and will integrate a seabed platform and a mooring line equipped with a set of different chemicalphysical and bio-ecological sensors. Ecological information from the two modules will be integrated by ad-hoc additional samplings in key moments and experimental activities aimed at contextualizing the sites at a larger scale. NEREA therefore aims at representing a first step towards the establishment of a network of augmented observatories, end-to-end approaches under the multidisciplinary framework required for ocean health assessment.

Nixon Bahamon, Jacopo Aguzzi, Miguel Ángel Ahumada-Sempoal, Joan Baptista Company, Charlotte Reuschel, Francesc Peters, Raffaele Bernardello, Joan Navarro, Zoila Velásquez, Antonio Cruzado
Stepped water warming effects on coastal ecosystem dynamics as monitored from fixed mooring stations in NW Mediterranean Sea

Average global land and ocean surface temperature has stepped up since 2014 above the average. The Mediterranean Sea temperature follows this global trend. The effects of the warming on coastal areas in the Mediterranean are worrying, as they are biodiversity hotspots. Atypical warmer summer periods in the Mediterranean have been pointed out as potential drivers of massive mortalities of deep-sea organisms. Multi-sensor mooring arrays are fundamental to assess the magnitude and effects of water warming. Analysis of long-term oceanographic and biogeochemical data collected in two fixed coastal observation stations in northwestern Mediterranean Sea reveals that marine oligotrophy has intensified since 2014, with increasing water temperature by 0.25°C, greater transparency and an earlier starting of the summer conditions. Phytoplankton biomass and nutrients show no apparent change of trends. Further studies are required to assess an eventual mismatch between the life cycles of the organisms and the expected environmental conditions. These fixed stations may be considered as reference monitoring locations to assess the effects of water warming on marine ecosystem functioning.

Matteo Cutugno, Umberto Robustelli, Giovanni Pugliano
Testing a GNSS software receiver for end-user utilization

Software Defined Receivers(SDR) can be a very useful tools both for researchers and surveyors since it is capable of extreme customization allowing user to access, visualize and modify signal processing blocks. In this paper we test the single point performance of the GNSS-SDR software receiver coupled with Nuand BladeRF x40 front-end feeded by an active u-blox GNSS antenna powered by a bias-tee needful to provide external gain. Four different tests have been carried out in two different scenarios located in Naples (Italy) employing two different antennas: the first dataset was acquired in a site expected to be a low-multipath environment while the second in a strong multipath scenario in Centro Direzionale (CDN) site using the same instrumentation. Both tests were carried out with two different antennas. Results achieved show how SDR is a good candidate to represent an innovative low-cost and flexible platform which can be used to get intermediate frequency data useful in the field of GNSS reflectometry and ionospheric scintillation analysis.

Salvatore Gaglione, Silvia Pennino, Vincenzo Piscopo, Antonio Scamardella
Absolute sea spectrum resampling from encounter wave time history

The aim of the work is to describe a practical and functional method to transform a wave energy spectrum from encounter frequency domain to absolute frequency domain. An important topic in the marine engineering field is the evaluation of the directional wave spectrum from the ship’s measured motions, however, when a ship advances in a seaway any spectrum estimation is directly in to the encounter frequency domain. A transformation from the encounter domain to the absolute domain, corresponding to observations from a fixed point in the inertial system, is necessary. Several cases have been examined, for different angles between the route and the prevailing sea state, to validate the presented technique showing accurate results for all the tested cases.

Anna Innac, Antonio Angrisano, Salvatore Gaglione, Nicola Crocetto
GPS precise positioning techniques for remote marine applications

Marine geodesy, offshore surveys and physical oceanography are usually related to the highly precise kinematic positioning of surveying platforms such as vessels, buoys and aircrafts. Currently, the Global Navigation Satellite Systems (GNSS) can provide a kinematic positioning accuracy of decimeter to centimeter level in relative mode, being potentially an appropriate choice for determining marine platform positions. However, these positioning techniques are related to the presence of reference stations and are not applicable in remote areas. In this work, two approaches are considered to determine the altitude variations of GPS antenna, which is an important parameter for the analysis of a ship motion. In detail, time-differencing of carrier phase measurements and precise point positioning approaches are applied on static data, collected by a single-frequency receiver, in order to assess the vertical variations performance.

Giovanni Battista Rossi, Francesco Crenna, Vincenzo Piscopo, Antonio Scamardella
Data processing for the accurate evaluation of sea-waves parameters

The monitoring of sea waves, either for weather forecasting or for comfort evaluation in navigation, typically includes spectrum measurement of wave elevation, either as the final result or as an intermediate step for the measurement of the relevant wave-motion parameters. Therefore, different spectrum estimation methods have been compared, by applying them to simulated wave-motion signals. Their performance is reported and guidelines for their application are provided.

Page 200 of 977 Results 1991 - 2000 of 9762