Deblurring of GLORIA side-scan sonar images     

D. C. Mason  T. P. LeBas  I. Sewell  C. Angelikaki 《Marine Geophysical Researches》1992,14(2):125-136

In side-scan sonars such as GLORIA, along-track resolution is usually much worse than across-track resolution. This paper shows how along-track resolution may be improved by the application of an image restoration (deblurring) technique known as the Jansson-van Cittert method. Employing a model of the image formation process, this involves iterated convolution of the estimated deblurred image radiances with the theoretical alongtrack point spread function. The method and its implementation for GLORIA images are described. Smoothing of high frequency noise prior to restoration has been found to lead to an improved end-product. The restored images exhibit sharper edges and a greater clarity much appreciated by the interpreter. This visual impression is borne out by quantitative measurement. The technique is shown to be a useful adjunct to the battery of digital preprocessing techniques which can be applied to the sonar image prior to the information extraction stage.  相似文献   

Contribution of the multibeam acoustic imagery to the exploration of the sea-bottom   总被引：1，自引：0，他引：1  

J. M. Augustin  R. Le Suave  X. Lurton  M. Voisset  S. Dugelay  C. Satra 《Marine Geophysical Researches》1996,18(2-4):459-486

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现代长江口水下底坡上的微地貌类型及分区     

陈卫民  杨作升  曹立华  郭志刚  刘浩  杜静萍 《中国海洋大学学报(自然科学版)》1993,(Z1)

旁侧扫描声纳记录真实地揭示出现代长江口水下底坡上发育的微地貌形态。指出微地貌的形态特征及其分布规律与长江泥沙的传输分布、长江口区海域的水动力机制密切相关。  相似文献   

Recording the migration behaviour of fish schools by multi-beam sonar during conventional acoustic surveys     

Hafsteinsson  M. T.; Misund  O. A. 《ICES Journal of Marine Science》1995,52(6):915-924

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Geometric corrections on sidescan sonar images based on bathymetry. Application with SeaMARC II and Sea Beam data     

Pierre Cervenka  Christian De Moustier  Peter F. Lonsdale 《Marine Geophysical Researches》1994,16(5):365-383

Acoustic backscatter images of the seafloor obtained with sidescan sonar systems are displayed most often using a flat bottom assumption. Whenever this assumption is not valid, pixels are mapped incorrectly in the image frame, yielding distorted representations of the seafloor. Here, such distortions are corrected by using an appropriate representation of the relief, as measured by the sonar that collected the acoustic backscatter information. In addition, all spatial filtering operations required in the pixel relocation process take the sonar geometry into account. Examples of the process are provided by data collected in the Northeastern Pacific over Fieberling Guyot with the SeaMARC II bathymetric sidescan sonar system and the Sea Beam multibeam echo-sounder. The nearly complete (90%) Sea Beam bathymetry coverage of the Guyot serves as a reference to quantify the distortions found in the backscatter images and to evaluate the accuracy of the corrections performed with SeaMARC II bathymetry. As a byproduct, the processed SeaMARC II bathymetry and the Sea Beam bathymetry adapted to the SeaMARC II sonar geometry exhibit a 35m mean-square difference over the entire area surveyed.On leave at the Naval Research Laboratory, Code 7420, Washington D.C. 20375-5350.  相似文献   

Processing Multibeam Backscatter Data   总被引：1，自引：0，他引：1  

Qiu-hua Tang  Xing-hua Zhou  Zhong-chen Liu  De-wen DU 《Marine Geodesy》2005,28(3):251-258

A new highly precise source of data has recently become available using multibeam sonar systems in hydrography. Multibeam sonar systems can provide hydrographic quality depth data as well as high-resolution seafloor sonar images. We utilize the seafloor backscatter strength data of each beam from multibeam sonar and the automatic classification technology so that we can get the seafloor type identification maps. In this article, analyzing all kinds of error effects in backscatter strength, data are based on the relationship between backscatter strength and seafloor types. We emphasize particularly analyzing the influences of local bottom slope and near nadir reflection in backscatter strength data. We also give the correction algorithms and results of these two influent factors. After processing the raw backscatter strength data and correcting error effects, we can get processed backscatter strength data which reflect the features of seafloor types only. Applying the processed backscatter strength data and mosaicked seafloor sonar images, we engage in seafloor classification and geomorphy interpretation in future research.  相似文献   

Progressive deformation of an evaporite-bearing accretionary complex: SeaMARC I,SeaBeam and piston-core observations from the Mediterranean Ridge     

Kim A. Kastens  Nancy A. Breen  Maria B. Cita 《Marine Geophysical Researches》1992,14(4):249-298

The Mediterranean Ridge is an arcuate ridge of deformed sediment caught up in the convergent plate margin between the African plate and the Aegean. An intensive campaign of SeaMARC I and SeaBeam surveys followed by piston coring has been conducted along the contact between undeformed turbidites of the Sirte Abyssal Plain and folded and faulted sediments of the Mediterranean Ridge. Along the outer edge of the Ridge, surficial sediments have been deformed into sinusoidal ridges and troughs (wavelengths 0.5–2 km, amplitude 20–150 m), which we interpret as folds. In plan view, the ridge and the trough fabric parallels the NW-SE trending regional contours, suggesting that the folds formed in response to compression orthogonal to the Mediterranean Ridge. The outermost ridge is shedding a debris apron out onto the abyssal plain, implying that uplift and deformation are ongoing. We show that the geometry of the outermost folds can be produced by elastic bending of a packet of 5–10 relatively strong layers, each 10–20 m thick, interbedded between weaker layers; we equate the strong layers with gypsum beds in the Messinian upper evaporites. Folding the seafloor from a flat layer into the observed ridge and trough topography would shorten the layer by less than 2%. Two percent shortening (equals two percent thickening) is insufficient to create the observed relief of the Mediterranean Ridge even if the entire sediment column down to basement were involved; we infer that additional shortening/thickening is accommodated by thrust faulting above a decollement at the top of the Messinian salt layer. At distances > 15 km from the deformation front and more than 500 m from the abyssal plain, sharp-edged, fine-grained side-scan lineations with very little vertical relief cut across the kilometer-scale ridge and trough topography. These fine-grained lineations fall in two groups trending N/S to NNE/SSW and ~ENE. We interpret these lineaments as traces of conjugate strike-slip faults formed in the same compressional regime which formed the NW/SE trending folds. The onset of strike-slip faulting may coincide with the cessation of imbricate thrust fan development above the initial salt-controlled decollement surface. The following characteristics of the Mediterranean Ridge are attributed to the presence of evaporites in the incoming sedimentary section: (1) initial deformation by folding rather than thrust faulting; (2) narrow taper; (3) rapid rate of outward growth; (4) karstification.  相似文献   

Ongoing methane discharge at well site 22/4b (North Sea) and discovery of a spiral vortex bubble plume motion     

《Marine and Petroleum Geology》2015

First direct evidence for ongoing gas seepage activity on the abandoned well site 22/4b (Northern North Sea, 57°55′ N, 01°38′ E) and discovery of neighboring seepage activity is provided from observations since 2005. A manned submersible dive in 2006 discovered several extraordinary intense seepage sites within a 60 m wide and 20 m deep crater cut into the flat 96 m deep seafloor. Capture and (isotope) chemical analyses of the gas bubbles near the seafloor revealed in situ concentrations of methane between 88 and 90%Vol. with δ¹³C–CH₄ values around −74‰ VPDB, indicating a biogenic origin. Bulk methane concentrations throughout the water column were assessed by 120 Niskin water samples showing up to 400.000 nM CH₄ in the crater at depth. In contrast, concentrations above the thermocline were orders of magnitude lower, with a median value of 20 nM. A dye tracer injection into the gas seeps revealed upwelling bubble and water motion with gas plume rise velocities up to ∼1 ms⁻¹ (determined near the seabed). However, the dissolved dye did not pass the thermocline, but returned down to the seabed. Measurements of direct bubble-mediated atmospheric flux revealed low values of 0.7 ± 0.3 kty⁻¹, much less than current state-of-the-art bubble dissolution models would predict for such a strong and upwelling in situ gas bubble flux at shallow water depths (i.e. ∼100 m).Acoustic multibeam water column imaging data indicate a pronounced 200 m lateral intrusion at the thermocline together with high methane concentration at this layer. A partly downward-orientated bubble plume motion is also visible in the acoustic data with potential short-circuiting in accordance to the dye experiment. This observation could partly explain the observed trapping of most of the released gas below the well-established thermocline in the North Sea. Moreover, 3D analyses of the multibeam water column data reveal that the upwelling plume transforms into a spiral expanding vortex while rising through the water column. Such a spiral vortex motion has never been reported before for marine gas seepage and might represent an important process with strong implication on plume dynamics, dissolution behavior, gas escape to the atmosphere, and is considered very important for respective modeling approaches.  相似文献   

多波束成像声纳系统低功耗设计     

崔海英  董琎琎  夏伟杰  窦法旺  蒋鹏飞  金雪 《海洋测绘》2015,35(3):71-74

针对多波束成像声纳系统降低系统功耗提高续航能力的要求,从硬件和算法两个方面展开了对系统的低功耗设计。硬件方面通过采用单电源运算放大器(OPA)电路架构对系统调理模块的放大、滤波链路进行了重新设计,实际测试结果表明实现了14.37W的系统功耗降低。算法方面通过提出一种基于圆阵的旋转多波束形成方法,在完成系统多波束设计的基础上实现了85倍的资源优化效果,为信号处理模块的FPGA芯片低功耗选型提供了技术支撑。  相似文献   

Volcanoes of the southwestern extension of the active Mariana island arc: New swath-mapping and geochemical studies   总被引：1，自引：0，他引：1  

P. FRYER    H. SUJIMOTO    M. SEKINE    L. E. JOHNSON    J. KASAHARA    H. MASUDA    T. GAMO    T. ISHII    M. ARIYOSHI  & K. FUJIOKA 《Island Arc》1998,7(3):596-607

Until recently it was thought that the volcanoes of the Mariana island arc of the western Pacific terminated at Tracey Seamount at ∼ 14°N immediately west of Guam. Sea floor mapping in 1995 shows a series of large volcanic seamounts stretching westward for nearly 300 km beyond that point. The morphology, spacing, and composition of those sampled are consistent with their having formed as a consequence of eruption of suprasubduction zone arc magmas. The relationships of the volcanoes to the tectonic processes of subduction of the Pacific plate beneath the southern portion of the Mariana convergent plate margin are becoming increasingly clear as new bathymetry and geochemical data are amassed. The volcanoes along this trend that lie closest to Guam are forming where the center of active extension in the back-arc basin intersects the line of arc volcanoes. They develop well-defined rifts that are parallel to rift structures along the extension center, whereas volcanoes of the spreading axis to the north are smaller than the frontal arc volcanoes and tend to form along lineaments. Compositions of lavas from these intersection volcanoes bear some similarities to back-arc basin basalt, but are on the whole well within the range of compositions for Mariana island arc lavas. The Pacific plate subducts nearly orthogonal to the strike of the trench along the southern part of the Mariana system and the distance to the arc line from the trench axis is only ∼ 150 km. Several deep fault-controlled canyons on the inner slope of the southern Mariana trench indicate an enhanced tectonic extension of this plate margin. The presence of these active arc volcanoes and the existence of the orthogonal normal faulting along the southern Mariana forearc supports a model of radial extension for formation of the Mariana Trough, a model previously dismissed because of the lack of evidence of these two major geological features.  相似文献