共查询到20条相似文献，搜索用时 671 毫秒
1.
T.F. Sutherland J. Galloway R. Loschiavo C.D. Levings R. Hare 《Estuarine, Coastal and Shelf Science》2007,75(4):447-458
Both acoustic and sediment surveys were carried out in the Broughton Archipelago, British Columbia, in order to map a former aquaculture site and calibrate acoustic surveys with georeferenced sediment properties. The acoustic surveys included EM3000 Multibeam (including backscatter) and QTC VIEW™ (Series IV) technologies, while the geotechnical survey entailed Van Veen grab sampling of surface sediments and associated analyses. The two acoustic technologies were consistent in their ability to identify distinct regions of seafloor characterized by rock outcrops, consolidated substrates, or gel-mud depositional fields. Both multibeam backscatter data and QTC VIEW™ number-coded classifications were extracted across a range of circular areas located at each georeferenced sampling station (radii: 2, 3, 4, 5, 8, 12, 16, 20 m). Statistical correlations were observed between backscatter and certain geotechnical properties, such as sediment porosity, sediment grain size fractions (<2 μm, silt content), and particulate sulfur concentration. The areal resolution of backscatter extraction was explored in terms of determining a sensitive calibration technique between backscatter and sediment properties. In general the highest r2 values between backscatter and sediment variables were observed across extraction radii between 8 and 20 m. Such groundtruthing techniques could be used to interpolate seafloor characteristics between sampling stations and provide a steering tool for sampling designs associated with benthic monitoring programs. 相似文献
2.
Magdalena Szuman Christian Berndt Colin Jacobs Angus Best 《Marine Geophysical Researches》2006,27(3):167-180
This study uses three acoustic instruments (different in their operating frequencies, 13, 3.5, and 6–10 kHz, and deployment
type, hull-mounted, surface-towed and deep-towed) to investigate and characterize the acoustic response of seafloor NE of
Oman in a frequency-independent manner. High-resolution control was achieved by having selected areas of our acoustic transects
ground-truthed by sampling and/or sea-floor photography. On the regional scale, the greatest degree of change in backscatter
amplitude was correlated with major changes of seabed morphology and lithology. However, small-scale roughness had the biggest
effect on amplitude on the local scale, i.e. within each area of specific seafloor type. The study also shows that seafloor
reflection amplitude changes are far more easily detected by deep-towed instrument than by surface-towed or hull-mounted systems.
Whilst there are significant changes in bioturbation types and density along the transects, the suite of instruments deployed
was not able to pick up the effect of the bioturbation on acoustic signals. 相似文献
3.
Rosa Freitas Leandro Sampaio Ana Maria Rodrigues Victor Quintino 《Estuarine, Coastal and Shelf Science》2005,65(4):625-632
An acoustic ground discrimination system (QTC VIEW, Series IV) was used to identify and map the bottom acoustic diversity in the bar channel of Ria de Aveiro, Western Portugal. The majority of the survey area presented shallow depth for this type of equipment, ranging mainly from 5 to 15 m. Depth occasionally reached 25 m in specific areas located across the entrance channel, dug by the strong tidal currents, reaching 3 m/s. The acoustic data were submitted to manual and auto-cluster and the results obtained from both procedures were coherent. Using aids to the acoustic classification and ground-truth sediment data, a final solution consisting of four acoustic classes was reached. Their geographical distribution was coincident with the spatial distribution of the major bottom types and sediment groups (hard bottom, coarse sand, medium sand and fine sand), identified through multivariate analysis of the grain-size data, and reflected the complex hydrodynamics of the entrance channel. The acoustic pattern was coincident at the intersections of the acoustic survey lines, assuring the repeatability of the acoustic procedure. Overall, the acoustic approach showed consistent results for the assessment and mapping of the benthic habitats in this shallow-water coastal area, providing a very valuable tool in an area where conventional sediment sampling is less favourable, namely due to strong tidal currents and frequent ship traffic, such as the entrance channel of Ria de Aveiro and the near-shore adjacent shelf. 相似文献
4.
Seafloor acoustic remote sensing with multibeam echo-sounders and bathymetric sidescan sonar systems 总被引：5，自引：0，他引：5
This paper examines the potential for remote classification of seafloor terrains using a combination of quantitative acoustic backscatter measurements and high resolution bathymetry derived from two classes of sonar systems currently used by the marine research community: multibeam echo-sounders and bathymetric sidescans sonar systems. The high-resolution bathymetry is important, not only to determine the topography of the area surveyed, but to provide accurate bottom slope corrections needed to convert the arrival angles of the seafloor echoes received by the sonars into true angles of incidence. An angular dependence of seafloor acoustic backscatter can then be derived for each region surveyed, making it possible to construct maps of acoustic backscattering strength in geographic coordinates over the areas of interest. Such maps, when combined with the high-resolution bathymetric maps normally compiled from the data output by the above sonar systems, could be very effective tools to quantify bottom types on a regional basis, and to develop automatic seafloor classification routines. 相似文献
5.
Evangelos Alevizos Mirjam Snellen Dick Simons Kerstin Siemes Jens Greinert 《Marine Geophysical Researches》2018,39(1-2):289-306
This study applies three classification methods exploiting the angular dependence of acoustic seafloor backscatter along with high resolution sub-bottom profiling for seafloor sediment characterization in the Eckernförde Bay, Baltic Sea Germany. This area is well suited for acoustic backscatter studies due to its shallowness, its smooth bathymetry and the presence of a wide range of sediment types. Backscatter data were acquired using a Seabeam1180 (180 kHz) multibeam echosounder and sub-bottom profiler data were recorded using a SES-2000 parametric sonar transmitting 6 and 12 kHz. The high density of seafloor soundings allowed extracting backscatter layers for five beam angles over a large part of the surveyed area. A Bayesian probability method was employed for sediment classification based on the backscatter variability at a single incidence angle, whereas Maximum Likelihood Classification (MLC) and Principal Components Analysis (PCA) were applied to the multi-angle layers. The Bayesian approach was used for identifying the optimum number of acoustic classes because cluster validation is carried out prior to class assignment and class outputs are ordinal categorical values. The method is based on the principle that backscatter values from a single incidence angle express a normal distribution for a particular sediment type. The resulting Bayesian classes were well correlated to median grain sizes and the percentage of coarse material. The MLC method uses angular response information from five layers of training areas extracted from the Bayesian classification map. The subsequent PCA analysis is based on the transformation of these five layers into two principal components that comprise most of the data variability. These principal components were clustered in five classes after running an external cluster validation test. In general both methods MLC and PCA, separated the various sediment types effectively, showing good agreement (kappa >0.7) with the Bayesian approach which also correlates well with ground truth data (r2?>?0.7). In addition, sub-bottom data were used in conjunction with the Bayesian classification results to characterize acoustic classes with respect to their geological and stratigraphic interpretation. The joined interpretation of seafloor and sub-seafloor data sets proved to be an efficient approach for a better understanding of seafloor backscatter patchiness and to discriminate acoustically similar classes in different geological/bathymetric settings. 相似文献
6.
Anne-Cathrin Wölfl Chai Heng Lim H. Christian Hass Sebastian Lindhorst Gabriela Tosonotto Karsten Alexander Lettmann Gerhard Kuhn Jörg-Olaf Wolff Doris Abele 《Geo-Marine Letters》2014,34(5):435-446
Marine habitats worldwide are increasingly pressurized by climate change, especially along the Antarctic Peninsula. Well-studied areas in front of rapidly retreating tidewater glaciers like Potter Cove are representative for similar coastal environments and, therefore, shed light on habitat formation and development on not only a local but also regional scale. The objective of this study was to provide insights into habitat distribution in Potter Cove, King George Island, Antarctica, and to evaluate the associated environmental processes. Furthermore, an assessment concerning the future development of the habitats is provided. To describe the seafloor habitats in Potter Cove, an acoustic seabed discrimination system (RoxAnn) was used in combination with underwater video images and sediment samples. Due to the absence of wave and current measurements in the study area, bed shear stress estimates served to delineate zones prone to sediment erosion. On the basis of the investigations, two habitat classes were identified in Potter Cove, namely soft-sediment and stone habitats that, besides influences from sediment supply and coastal morphology, are controlled by sediment erosion. A future expansion of the stone habitat is predicted if recent environmental change trends continue. Possible implications for the Potter Cove environment, and other coastal ecosystems under similar pressure, include changes in biomass and species composition. 相似文献
7.
A methodology for acoustic seafloor classification 总被引：3，自引：0，他引：3
A seafloor classification methodology, based on a parameterization of the reverberation probability density function in conjunction with neural network classifiers, is evaluated through computer simulations. Different seafloor provides are represented by a number of scatterer distributions exhibiting various degrees of departure from the nominal Poisson distribution. Using a computer simulation program, these distributions were insonified at different spatial scales by varying the transmitted pulse length. The statistical signature obtained consists of reverberation kurtosis estimates as a function of pulse length. Two neural network classifiers are presented with the task of discriminating among the various scatterer distributions based on obtained acoustic signatures. The results indicate that this approach offers considerable promise for practical, realizable solutions to the problem of remote seafloor classification 相似文献
8.
Sidescan sonar image processing techniques 总被引：1，自引：0，他引：1
A four-step processing sequence is described to produce image mosaics from the various segments of a sidescanned acoustic imaging survey of a given seafloor area. Starting with data consisting for each ping of acoustic backscatter levels versus horizontal range across-track, median prefiltering is used first to reduce the influence of outliers on subsequent linear processes. Artifacts that are clearly unrelated to the backscattering properties of the seafloor are then isolated on a ping by ping basis through a spectral analysis that relies on a decomposition using Chebyshev polynomials to filter the low spatial frequency components of the image. Contrast enhancement is then achieved through an original implementation of the classical gray level histogram equalization technique by balancing local versus global histogram contributions. Pixels are mapped on a geographic grid taking due account of the geometry of the measurement and of the spacing between pings to minimize along-track smearing of features. Examples of results obtained with these processing techniques are given for SeaMARC II data recorded during a complete survey of Fieberling Guyot (32°.5 N, 128° W) 相似文献
9.
10.
《African Journal of Marine Science》2013,35(1):99-109
Schools of horse mackerel Trachurus trachurus capensis, sardine Sardinops sagax and round herring Etrumeus whiteheadi were surveyed by conventional echo-integration along systematic transects. The transects were surveyed twice, in opposite directions. Clupeoid biomass was concentrated in a few dense aggregations, whereas horse mackerel were less dense and distributed over larger areas. The influence of aggregation patterns of the different species on the precision of the acoustic estimates was analysed with respect to spatial variability and diurnal effects. Isotropic variograms computed from values of acoustic back-scattering strength showed little or no structure for all three species. Indicator variograms showed relatively large structures (>15 miles) for all three species at the lowest cut-off level, confirming the influence of high values on the variograms. The autocorrelation range decreased with an increase in cut-off value for horse mackerel, whereas variograms of sardine and round herring showed no structure at larger cut-off values. There were large variances in estimated biomass for sardine (77%) and round herring (90%) between surveys, whereas biomass estimates of horse mackerel were relatively similar between surveys. 相似文献
11.
Rosa Freitas Ana Maria Rodrigues Edward Morris Jose Lucas Perez-Llorens Victor Quintino 《Estuarine, Coastal and Shelf Science》2008,78(4):613-622
The single-beam acoustic ground discrimination system QTC View, Series V, was used in the Bay of Cadiz, Southwest Spain, for the identification and mapping of the bottom acoustic diversity. The acoustic data were obtained through two successive surveys, each conducted with one of the following echo sounder frequencies: 50 kHz and 200 kHz. The performance of each survey frequency for the identification of the sedimentary gradients was analyzed. The surveys were conducted during high tide given that the majority of the surveyed area is shallower than 5 m, although depth may occasionally reach 20 m in specific areas located in a navigation channel. The acoustic data obtained at the two different frequencies were, individually, submitted to manual clustering and a final solution consisting of three acoustic classes was reached for both datasets. However, only the geographical distribution of the acoustic classes obtained with 50 kHz echo sounder frequency was coincident with the spatial distribution of the superficial sediment groups (silty medium sand, very silty fine sand and mud), identified through multivariate analysis of the grain-size data of ground-truth sediment samples. The results obtained with the 200 kHz echo sounder frequency did not match the sedimentary gradients obtained for the area surveyed, not even the separation of muddy and sandy areas. 相似文献
12.
An overview of SAX99: acoustic measurements 总被引：5，自引：0，他引：5
Thorsos E.I. Williams K.L. Chotiros N.P. Christoff J.T. Commander K.W. Greenlaw C.F. Holliday D.V. Jackson D.R. Lopes J.L. McGehee D.E. Piper J.E. Richardson M.D. Dajun Tang 《Oceanic Engineering, IEEE Journal of》2001,26(1):4-25
A high-frequency acoustic experiment was performed at a site 2 km from shore on the Florida Panhandle near Fort Walton Beach in water of 18-19 m depth. The goal of the experiment was, for high-frequency acoustic fields (mostly In the 10-300-kHz range), to quantify backscattering from the seafloor sediment, penetration into the sediment, and propagation within the sediment. In addition, spheres and other objects were used to gather data on acoustic detection of buried objects. The high-frequency acoustic interaction with the medium sand sediment was investigated at grazing angles both above and below the critical angle of about 30°. Detailed characterizations of the upper seafloor physical properties were made to aid in quantifying the acoustic interaction with the seafloor. Biological processes within the seabed and the water column were also investigated with the goal of understanding their impact on acoustic properties. This paper summarizes the topics that motivated the experiment, outlines the scope of the measurements done, and presents preliminary acoustics results 相似文献
13.
During RV SONNE cruise SO-79 to the eastern Pacific Ocean, two areas of about 65×80 km in the northern Peru Basin were surveyed with the acoustic mapping systems HYDROSWEEP (bathymetry), PARASOUND (3.5 kHz high-resolution seismic system), and a deep-towed side-scan sonar system. In addition, we sampled sediments using piston and box corers. The data show an unexpected variability of seafloor features: The bathymetry is characterized by an abyssal hill topography with predominately N-S ridges up to 300 m high, and scattered volcanic hills. Moreover, one 2000-m-high seamount was mapped. PARASOUND shows several distinct reflectors within the sediment cover, all of which are attributed to carbonate-rich strata. In the northern area, the uppermost prominent reflector is related to the Mid-Brunhes Event (0.45 Ma) in the sediment cores, while the lowermost represents acoustic basement. In the southern area, the seismic pattern reveals an upper opaque zone and a lower transparent zone. The base of the opaque zone is marked by a distinct reflector which corresponds to a huge carbonate peak (6–7 Ma) in the sediment cores. However, despite this general pattern, the PARASOUND records show a highly variable situation, with the distribution of sediment echo types strongly influenced by the seafloor topography. The side-scan sonar revealed the existence of numerous small volcanic cones up to 25 m high and nearly free of sediment. Additionally, the sonar records show a patchy (up to 800 m across) seafloor reflectiviti. We interpret this patchiness as a local lack of manganese nodule coverage. Volcanic cones and the most distinct nodule-free patches are usually on ridges. We interpret this variability as caused by winnowing and erosion, an interpretation that is supported by the occurrence of outcrops of Tertiary strata. This regional small-scale variability argues for a highly dynamic depositional history of the Peru Basin. 相似文献
14.
15.
Seafloor mounds are potential geohazards to offshore rig emplacement and drilling operations and may contain evidence of underlying petroleum systems. Therefore, identifying and mapping them is crucial in de-risking exploration and production activities in offshore domains.A 738 km2 high resolution three-dimensional seismic dataset was used to investigate the occurrence, seismic characteristics and distribution of features interpreted as seafloor and buried sediment mounds, at water-depths of 800–1600 m, on the western Niger Delta slope. Fifteen seafloor mounds and eighteen shallowly buried mounds were identified. The seafloor mounds are characterised by lower seismic amplitude anomalies than the surrounding seabed sediments, and overlie vertical zones of acoustic blanking. The buried mounds in contrast are characterised by high amplitude anomalies; they also directly overlie sub-vertical zones of acoustic blanking. Seismic evidences from the features, their distribution patterns and tectono-stratigraphic associations suggest that their formation was controlled by the juxtaposition of buried channels and structural highs and their formation caused by focused fluid flow and expulsion of entrained sediments at the seabed.Considering the acoustic and geometrical characteristics of the mounds and comparing them with mound-shaped features from around the world, we conclude that the mounds most likely comprise heterolithic seafloor extrusions of muds and sands from the Agbada Formation with gas and possibly oil in some of the pore space giving rise to the acoustic characteristics. 相似文献
16.
17.
Lei Sun Xiangmei Meng Guanbao Li Guangming Kan Baohua Liu 《Marine Georesources & Geotechnology》2020,38(5):595-603
AbstractThe high-frequency acoustic properties of seafloor sediments are very significant in seafloor study and underwater acoustic study field. In order to measure the sound speed and the attenuation for the small-scale sediment cores more accurately, this study developed a water coupled acoustic laboratory measurement system based on Richardson-Briggs technique. This method used the correlation comparison of waveforms received in sediment core and in identical reference tubes filled with water to measure sound speed and attenuation. The sound speed and attenuation of a clayey silt sediment sample were measured using the water coupled acoustic laboratory measurement system. This frequency dependence of the sound speed and attenuation showed that the clayey silt sediment has a weak positive sound speed dispersion, while the attenuation increases with a strong positive gradient within the measurement frequency range. This study also noted that the measured sound speed ratio match well with the empirical equations from literature. The measured attenuation factor data can fall in the Hamilton’s empirical prediction range. 相似文献
18.
The spring-spawning Baltic Sea herring spawn in coastal areas that also serve as nursery areas for the young fish during their first summer. In a bay known as a herring spawning and nursery area, the pelagic fish abundance was quantified using hydroacoustics every second week from late spring to autumn in 2000 and 2001. A dense system of survey transects allowed determination of the acoustic index (the nautical area scattering coefficient) for fish abundance with high precision. The variation, expressed as the geostatistical coefficient of variation, was on average 5% both years and ranged from 3–11% (2000) and 3–8% (2001). Through the hydroacoustic data intra-annual dynamics in acoustic fish abundance, densities and size composition could be followed, which showed similar trends in both years. In spring and early summer acoustic fish densities were low, followed by a drastic, 20-fold increase in late summer. Hydroacoustic data and biological samples suggest that the increase was caused mainly by the recruitment of young-of-the-year herring to the acoustically assessable pelagic fish community. This age class is commonly not well represented in catches when using traditional sampling gears such as gill nets and trawls, and hydroacoustics may help to improve quantitative estimates of small juvenile fish in order to increase the understanding of biological processes in coastal nursery areas. 相似文献
19.
Narumi Takahashi Yasuhisa Ishihara Hiroshi Ochi Tatsuya Fukuda Jun’ichiro Tahara Yosaku Maeda Motoyuki Kido Yusaku Ohta Katsuhiko Mutoh Gosei Hashimoto Satoshi Kogure Yoshiyuki Kaneda 《Marine Geophysical Researches》2014,35(3):243-253
We have developed a new system for real-time observation of tsunamis and crustal deformation using a seafloor pressure sensor, an array of seafloor transponders and a Precise Point Positioning (PPP ) system on a buoy. The seafloor pressure sensor and the PPP system detect tsunamis, and the pressure sensor and the transponder array measure crustal deformation. The system is designed to be capable of detecting tsunami and vertical crustal deformation of ±8 m with a resolution of less than 5 mm. A noteworthy innovation in our system is its resistance to disturbance by strong ocean currents. Seismogenic zones near Japan lie in areas of strong currents like the Kuroshio, which reaches speeds of approximately 5.5 kt (2.8 m/s) around the Nankai Trough. Our techniques include slack mooring and new acoustic transmission methods using double pulses for sending tsunami data. The slack ratio can be specified for the environment of the deployment location. We can adjust slack ratios, rope lengths, anchor weights and buoy sizes to control the ability of the buoy system to maintain freeboard. The measured pressure data is converted to time difference of a double pulse and this simple method is effective to save battery to transmit data. The time difference of the double pulse has error due to move of the buoy and fluctuation of the seawater environment. We set a wire-end station 1,000 m beneath the buoy to minimize the error. The crustal deformation data is measured by acoustic ranging between the buoy and six transponders on the seafloor. All pressure and crustal deformation data are sent to land station in real-time using iridium communication. 相似文献
20.
Chan Min Yoo Jongmin Joo Sang Hoon Lee Youngtak Ko Sang-Bum Chi Hyung Jeek Kim Inah Seo Kiseong Hyeong 《Ocean Science Journal》2018,53(2):381-394
A high level of confidence in resource data is a key prerequisite for conducting a reliable economic feasibility study in deep water seafloor mining. However, the acquisition of accurate resource data is difficult when employing traditional point-sampling methods to assess the resource potential of polymetallic nodules, given the vast size of the survey area and high spatial variability in nodule distribution. In this study, we analyzed high-resolution acoustic backscatter intensity images to estimate nodule abundance and increase confidence levels in nodule abundance data. We operated a 120 kHz deep-towed sidescan sonar (DSL-120) system (1×1 m resolution) across a 75 km2 representative area in the Korean Exploration Area for polymetallic nodules in the Northeastern Equatorial Pacific. A deep-towed camera system was also run along two tracks in the same area to estimate the abundance of polymetallic nodules on the seafloor. Backscatter data were classified into four facies based on intensity. The facies with the weakest and strongest backscatter intensities occurred in areas of high slope gradient and basement outcrops, respectively. The backscatter intensities of the two other facies correlated well with the nodule abundances estimated from still-camera images. A linear fit between backscatter intensity and mean nodule abundance for 10 zones in the study area yielded an excellent correlation (r2 = 0.97). This allowed us to compile a map of polymetallic nodule abundance that shows greater resolution than a map derived from the extrapolation of point-sampling data. Our preliminary analyses indicate that it is possible to greatly increase the confidence level of nodule resource data if the relationship between backscatter intensity and nodule abundance is reliably established. This approach has another key advantage over point sampling and image analyses in that detailed maps of mining obstacles along the seafloor are produced when acquiring data on the abundance of polymetallic nodules. The key limitation of this work is a poor correlation between nodule coverage, as observed from photographs, and nodule abundance. Significant additional ground truth sampling using well located box cores should be completed to determine whether or not there is a real correlation between the backscatter and abundance. 相似文献