Search

In this paper, we present a full coverage path planning (CPP) algorithm for the marine surveys conducted in the convex polygon shaped search area. The survey is supposed to carry out by torpedo-type AUVs (autonomous underwater vehicles). Due to their nonholonomic mechanical characteristics, these vehicles have nonzero minimum turning radius. For any given polygon shaped search area, it can always be partitioned into one or more convex polygons. With this in mind, this paper proposes a novel search algorithm called CbSPSA (Calculation based Shortest Path Search Algorithm) for full coverage of any given convex polygon shaped search area. By aligning the search inter-tracks alongside the edge with the minimum height, we can guarantee the minimum number of the vehicle's turns. In addition, the proposed method can guarantee the planned path is strictly located inside the polygon area without overlapped or crossed path lines, and also has the total path length as short as possible. Considering the vehicle's nonzero minimum turning radius, we also propose a sort of smoothing algorithm which can smooth the waypoint path searched by CbSPSA so that the vehicle can exactly follow it. The smoothed path is also guaranteed to be strictly located inside the polygon. Numerical simulation analyses are also carried out to verify the effectiveness of the proposed schemes. [ABSTRACT FROM AUTHOR]

In this paper, we present a full coverage path planning (CPP) algorithm for the marine surveys conducted in the convex polygon shaped search area. The survey is supposed to carry out by torpedo-type AUVs (autonomous underwater vehicles). Due to their nonholonomic mechanical characteristics, these vehicles have nonzero minimum turning radius. For any given polygon shaped search area, it can always be partitioned into one or more convex polygons. With this in mind, this paper proposes a novel search algorithm called CbSPSA (Calculation based Shortest Path Search Algorithm) for full coverage of any given convex polygon shaped search area. By aligning the search inter-tracks alongside the edge with the minimum height, we can guarantee the minimum number of the vehicle’s turns. In addition, the proposed method can guarantee the planned path is strictly located inside the polygon area without overlapped or crossed path lines, and also has the total path length as short as possible. Considering the vehicle’s nonzero minimum turning radius, we also propose a sort of smoothing algorithm which can smooth the waypoint path searched by CbSPSA so that the vehicle can exactly follow it. The smoothed path is also guaranteed to be strictly located inside the polygon. Numerical simulation analyses are also carried out to verify the effectiveness of the proposed schemes.

With the in-depth implementation of the strategy of maritime power, the state has gradually increased its financial input in marine survey and research, and the number of ocean observation instruments and equipment in maritime research institutes has increased substantially. At the same time, due to the particularity of the use of ocean observation instruments and equipment, damage or even loss of instruments and equipment sometimes occurs, which has brought new challenges to the management of instruments and equipment. Taking the ocean observation instruments related to physical oceanography as an example, this paper classified the ocean observation instruments and equipment, discussed their particularity, explored the establishment of management mechanisms in line with the characteristics of ocean observation instruments and equipment, further improved the scientific nature of asset management, to better serve the needs of teaching and scientific research.

The present analysis of state of the art portrays that actual time series or spectrum backscattered data from a point on the sea bottom are rarely used as features for machine learning models. The paper deals with the artificial intelligence techniques used to examine CHIRP-recorded data. The data were collected using a CHIRP sub-bottom profiler to study two sand bottom sites and two sandstone bottom sites in the offshore zone of Ashqelon City (Southern Israel). The first reflection time series and spectra of all the traces from the four sites generated two training and two test sets. Two logistic regression models were trained using the training sets and evaluated for accuracy using the test sets. The examination results indicate that types of sea bottom can be quantitatively characterized by applying logistic regression models to either the backscatter time series of a frequency-modulated signal or the spectrum of that backscatter. The examination accuracy reached 90% for the time series and 94% for the spectra. The application of spectral data as features for more advanced machine learning algorithms and the advantages of their combination with other types of data have great potential for future research and the enhancement of remote marine soil classification. [ABSTRACT FROM AUTHOR]

The primary objective of this research is to demonstrate advanced surveying methods and techniques for coastal erosion identification and monitoring in a densely human-populated coastline, the southern coastline of the Gulf of Patras (Greece), which diachronically suffers erosion problems expected to become worse in the forthcoming years due to climate change and human intervention. Its importance lies in the fact that it presents a robust methodology on how all modern scientific knowledge and techniques should be used in coastal erosion problems. The presented methods include the use of satellite and aerial photo imaging, shallow seabed bathymetry and morphology, sediment sampling, geotechnical investigations, as well as hydrodynamic modelling. The results are extensively analyzed in terms of their importance in coastal erosion studies and are cross-validated to define those areas most vulnerable to erosion. Towards this scope, the seabed erosion rate produced by hydrodynamic modelling is compared with the coastal vulnerability index (CVI) calculations performed in the examined area to identify which coastal zones are under a regime of intensive erosion. The results between the CVI and the seabed erosion rate appear to coincide in terms of the erosion potential, especially in zones where the vulnerability regime has been calculated as being high or very high, with the P. oceanica meadows playing an important role in reducing erosion. [ABSTRACT FROM AUTHOR]

Recently, rapidly developing artificial intelligence and computer vision techniques have provided technical solutions to promote production efficiency and reduce labor costs in aquaculture and marine resource surveys. Traditional manual surveys are being replaced by advanced intelligent technologies. However, underwater object detection and recognition are suffering from the image distortion and degradation issues. In this work, automatic monitoring of sea cucumber in natural conditions is implemented based on a state-of-the-art object detector, YOLOv7. To depress the image distortion and degradation issues, image enhancement methods are adopted to improve the accuracy and stability of sea cucumber detection across multiple underwater scenes. Five well-known image enhancement methods are employed to improve the detection performance of sea cucumber by YOLOv7 and YOLOv5. The effectiveness of these image enhancement methods is evaluated by experiments. Non-local image dehazing (NLD) was the most effective in sea cucumber detection from multiple underwater scenes for both YOLOv7 and YOLOv5. The best average precision (AP) of sea cucumber detection was 0.940, achieved by YOLOv7 with NLD. With NLD enhancement, the APs of YOLOv7 and YOLOv5 were increased by 1.1% and 1.6%, respectively. The best AP was 2.8% higher than YOLOv5 without image enhancement. Moreover, the real-time ability of YOLOv7 was examined and its average prediction time was 4.3 ms. Experimental results demonstrated that the proposed method can be applied to marine organism surveying by underwater mobile platforms or automatic analysis of underwater videos. [ABSTRACT FROM AUTHOR]

Modern studies which dealt with the frequency domain analysis showed that a frequency-domain approach has an essential advantage and mentioned an inner qualitative relationship between the subsurface structure and its frequency spectra. This paper deals with the acoustic spectral response of sand and sandstone sediments at the sea bottom. An acoustic data collection campaign was conducted over two sand sites and two sandstone sites. The analysis of the results shows that reflections of acoustic signals from sand and sandstone sea bottom are characterized by various spectral features in the 2.75–6.75 kHz range. The differences in acoustic response of sand and sandstone can be quantified by examining the maximal normalized reflected power, the mean frequency, and the number of crossings at different power levels. The statistical value distribution of these potential classifiers was calculated and analyzed. These classifiers, and especially the roughness of the spectrum quantified by the number of crossings parameter can give information to assess the probability for sand or sandstone based on the reflected spectra and be used for actual distinction between sand and sandstone in sub bottom profiler data collection campaigns. [ABSTRACT FROM AUTHOR]

Marine survey unmanned surface vessel (USV) has a wide range of applications.However, the attitude of USV is easily affected by wind, waves, currents and floating debris, which may cause structural damage or low precision observation.Double hull and wide deck platform of unmanned surface vessed was designed, and the transducer of multi-beam echo sounder was installed on the lifting mechanism.These designs improved the sailing attitude of the platform, the safety of the transducer and the accuracy of the observed data.In 2020, this USV was participated in the dike-inspection mission of Jiangxi’s emergency flood relief.It successfully inspected the sediment environment of 14 km dike, affected by the unfavorable working conditions like rapid water flow, turbid water and floating garbage.Four risks were located, which provided important data support for the anti-flood campaign.

The present analysis of state of the art portrays that actual time series or spectrum backscattered data from a point on the sea bottom are rarely used as features for machine learning models. The paper deals with the artificial intelligence techniques used to examine CHIRP-recorded data. The data were collected using a CHIRP sub-bottom profiler to study two sand bottom sites and two sandstone bottom sites in the offshore zone of Ashqelon City (Southern Israel). The first reflection time series and spectra of all the traces from the four sites generated two training and two test sets. Two logistic regression models were trained using the training sets and evaluated for accuracy using the test sets. The examination results indicate that types of sea bottom can be quantitatively characterized by applying logistic regression models to either the backscatter time series of a frequency-modulated signal or the spectrum of that backscatter. The examination accuracy reached 90% for the time series and 94% for the spectra. The application of spectral data as features for more advanced machine learning algorithms and the advantages of their combination with other types of data have great potential for future research and the enhancement of remote marine soil classification.

The primary objective of this research is to demonstrate advanced surveying methods and techniques for coastal erosion identification and monitoring in a densely human-populated coastline, the southern coastline of the Gulf of Patras (Greece), which diachronically suffers erosion problems expected to become worse in the forthcoming years due to climate change and human intervention. Its importance lies in the fact that it presents a robust methodology on how all modern scientific knowledge and techniques should be used in coastal erosion problems. The presented methods include the use of satellite and aerial photo imaging, shallow seabed bathymetry and morphology, sediment sampling, geotechnical investigations, as well as hydrodynamic modelling. The results are extensively analyzed in terms of their importance in coastal erosion studies and are cross-validated to define those areas most vulnerable to erosion. Towards this scope, the seabed erosion rate produced by hydrodynamic modelling is compared with the coastal vulnerability index (CVI) calculations performed in the examined area to identify which coastal zones are under a regime of intensive erosion. The results between the CVI and the seabed erosion rate appear to coincide in terms of the erosion potential, especially in zones where the vulnerability regime has been calculated as being high or very high, with the P. oceanica meadows playing an important role in reducing erosion.

Recently, rapidly developing artificial intelligence and computer vision techniques have provided technical solutions to promote production efficiency and reduce labor costs in aquaculture and marine resource surveys. Traditional manual surveys are being replaced by advanced intelligent technologies. However, underwater object detection and recognition are suffering from the image distortion and degradation issues. In this work, automatic monitoring of sea cucumber in natural conditions is implemented based on a state-of-the-art object detector, YOLOv7. To depress the image distortion and degradation issues, image enhancement methods are adopted to improve the accuracy and stability of sea cucumber detection across multiple underwater scenes. Five well-known image enhancement methods are employed to improve the detection performance of sea cucumber by YOLOv7 and YOLOv5. The effectiveness of these image enhancement methods is evaluated by experiments. Non-local image dehazing (NLD) was the most effective in sea cucumber detection from multiple underwater scenes for both YOLOv7 and YOLOv5. The best average precision (AP) of sea cucumber detection was 0.940, achieved by YOLOv7 with NLD. With NLD enhancement, the APs of YOLOv7 and YOLOv5 were increased by 1.1% and 1.6%, respectively. The best AP was 2.8% higher than YOLOv5 without image enhancement. Moreover, the real-time ability of YOLOv7 was examined and its average prediction time was 4.3 ms. Experimental results demonstrated that the proposed method can be applied to marine organism surveying by underwater mobile platforms or automatic analysis of underwater videos.

Modern studies which dealt with the frequency domain analysis showed that a frequency-domain approach has an essential advantage and mentioned an inner qualitative relationship between the subsurface structure and its frequency spectra. This paper deals with the acoustic spectral response of sand and sandstone sediments at the sea bottom. An acoustic data collection campaign was conducted over two sand sites and two sandstone sites. The analysis of the results shows that reflections of acoustic signals from sand and sandstone sea bottom are characterized by various spectral features in the 2.75–6.75 kHz range. The differences in acoustic response of sand and sandstone can be quantified by examining the maximal normalized reflected power, the mean frequency, and the number of crossings at different power levels. The statistical value distribution of these potential classifiers was calculated and analyzed. These classifiers, and especially the roughness of the spectrum quantified by the number of crossings parameter can give information to assess the probability for sand or sandstone based on the reflected spectra and be used for actual distinction between sand and sandstone in sub bottom profiler data collection campaigns.

Copyright of Telecommunications Science is the property of Beijing Xintong Media Co., Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The tightly coupled global navigation satellite system (GNSS) precise point positioning (PPP) and inertial navigation system (INS) can provide high-precision position, velocity and attitude information. The coupled system utilizes single receiver, which is particularly suitable for the environment without reference station, such as marine survey. In the former works, the integer ambiguity resolution of PPP/INS in terrestrial environment is researched. However, the GNSS observation is severely affected by the multipath effect in marine environment. In addition, the sideslip caused by wind and sea wave also impact float ambiguity estimation, consequently introducing difficulty for PPP ambiguity fixing. Therefore, the PPP/INS tightly coupled model with fixed ambiguity is proposed for marine survey. The correction model of INS gyroscope bias in closed-loop is deduced in detail. The influence of ship motion noise and multipath in marine environment is reduced by introducing the robust factor to the Kalman filter. The feasibility of the method is verified in a real marine experiment, with a detail evaluation of the data quality and positioning accuracy. The results show that the accuracy of PPP/INS can reach centimeter level after fixing the ambiguity in marine environment. Furthermore, the precise INS-predicted position can significantly shorten the re-fixed time of PPP/INS, which proves the efficiency of the proposed approach. [ABSTRACT FROM AUTHOR]

The nation of Antigua and Barbuda has experienced major degradation of its coral reef ecosystems over the past 40+ years. The primary drivers of this degradation are multiple and are highly linked to anthropogenic influences, including over-exploitation and poor management of marine resources. The effectiveness of management actions in marine protected areas (MPAs) has often been hampered by a lack of data to inform management recommendations. This was emphasized by The Nature Conservancy’s (TNC) Coral Reef Report Card which highlighted not only the lack of data collection in Antigua and Barbuda and other Caribbean nations, but also illustrated how spatially dispersed available datasets are. The government of Antigua and Barbuda recognized the need for a marine data collection program to better inform the designation and management of MPAs as a tool to improve the health of the marine ecosystems. The Atlantic Gulf Rapid Reef Assessment (AGRRA) protocol has been identified as a means to address planning and management for marine areas. Three AGRRA surveys have been conducted in the years following the TNC 2016 report, in previously established managed areas: North East Marine Management Area (NEMMA) in 2017 and Nelson Dockyard National Park (NDNP) in 2019 as well as areas outlined for future management (Redonda in 2018). Our surveys were conducted to provide updated datasets to inform management for the aforementioned areas. While the results of these surveys mirror the underlying poor coral reef-health conditions, which have been shown to exist within the Caribbean region, they also highlight intra-site variation that exists within each survey location. This knowledge can be crucial in guiding management decisions in these marine areas, through zoning and other management prescriptions. Additionally, the marine surveys conducted around Redonda established useful marine baselines to aid in monitoring the island’s recovery following removal of terrestrial invasive species. This article provides an overview of data collected using the AGRRA methodology in marine zones across Antigua and Barbuda which have current or future management prescriptions and provides recommendations to demonstrate the data’s future utilization for marine conservation and management.

Copyright of Hydrographic Surveying & Charting / Haiyang Cehui is the property of Hydrographic Surveying & Charting Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The nation of Antigua and Barbuda has experienced major degradation of its coral reef ecosystems over the past 40+ years. The primary drivers of this degradation are multiple and are highly linked to anthropogenic influences, including over-exploitation and poor management of marine resources. The effectiveness of management actions in marine protected areas (MPAs) has often been hampered by a lack of data to inform management recommendations. This was emphasized by The Nature Conservancy's (TNC) Coral Reef Report Card which highlighted not only the lack of data collection in Antigua and Barbuda and other Caribbean nations, but also illustrated how spatially dispersed available datasets are. The government of Antigua and Barbuda recognized the need for a marine data collection program to better inform the designation and management of MPAs as a tool to improve the health of the marine ecosystems. The Atlantic Gulf Rapid Reef Assessment (AGRRA) protocol has been identified as a means to address planning and management for marine areas. Three AGRRA surveys have been conducted in the years following the TNC 2016 report, in previously established managed areas: North East Marine Management Area (NEMMA) in 2017 and Nelson Dockyard National Park (NDNP) in 2019 as well as areas outlined for future management (Redonda in 2018). Our surveys were conducted to provide updated datasets to inform management for the aforementioned areas. While the results of these surveys mirror the underlying poor coral reef-health conditions, which have been shown to exist within the Caribbean region, they also highlight intra-site variation that exists within each survey location. This knowledge can be crucial in guiding management decisions in these marine areas, through zoning and other management prescriptions. Additionally, the marine surveys conducted around Redonda established useful marine baselines to aid in monitoring the island's recovery following removal of terrestrial invasive species. This article provides an overview of data collected using the AGRRA methodology in marine zones across Antigua and Barbuda which have current or future management prescriptions and provides recommendations to demonstrate the data's future utilization for marine conservation and management. [ABSTRACT FROM AUTHOR]

The processing of Chirp data is limited by the usual recording of the signal envelope, which enhances its immediate visibility but prevents applying methods based on wave equations. This is normally not the case for Boomer data. However, both systems are monochannel instruments, which cannot estimate properly the propagation velocity of the signal in the rocks. In this paper, we present two theorems: the first one links the Chirp or Boomer source spectrum with an expected amplitude decay curve; the second one defines conditions for the deconvolution stability of the enveloped Boomer signal when the full waveform of the source signal is known. In this way, we can jointly process and integrate heterogeneous surveys including both data types. We validated the proposed algorithms by applying them to synthetic and real data. The presented tools can improve the image resolution and the characterization of geological formations in marine surveys by reflectivity anomalies, which are distorted by standard equalization methods.

Indonesia is a maritime country with two-third of its total area consist of water. Research on marine and fisheries studies should be considered as an important matter in Indonesia. Studies on research development can be a way to evaluate and to determine research policy direction. The increasing of scientific publication database draws the need for enhancement to their quantitative techniques analysis to understand research structure; social and science structure. This study aims to map the subject area, that covered research on marine and fisheries studies and carried out by institution located in Indonesia. Social network analysis is used to show the relationship of subject area in the related research. Data that is used in this research is based on marine and fisheries studies that conducted in Indonesia and indexed by Scopus for the last ten years (2006-2015). The network map shows that the publication has changed in terms of the covered subject areas and the relationship among them. The result of this study can be used to evaluate and to support marine and fisheries research policy direction in Indonesia.

Based on the ongoing techniques among control theory, communication networks, and sensor design, unmanned aerial vehicles (UAVs), unmanned undersea vehicles (UUVs) and unmanned surface vehicles (USVs) are experiencing rapid development. Research on these unmanned systems and those intelligent sectors inside has absorbed interests and investments from not only military but also civil organizations. The well-applied fields include surveillance and reconnaissance, surface warfare, antisubmarine warfare, mine countermeasures, oceanic environment monitoring, search and rescue, hydrographic survey, and so on. Comparing with those studies on UAVs and UUVs, the one focusing on USVs was started later and has been developed quickly in the past 20 years. Since 2013, USV has advanced considerably in China, particularly in the marine survey field. Owing to its characteristics of light-weighting, intelligence, and unmanned operations, USV is attractive for shallow water, extreme environments, and marine accidents. This paper comprehensively summarizes the recent progress of the marine survey USV in China. The structure of the paper is divided into three parts. First, we briefly recall the developing history and introduce several excellent USVs of China in recent years. The marine survey USVs invested by the State Oceanic Administration (SOA) are then summarized in the next section, along with the details of hydrographic survey in the South China Sea, Antarctic marine survey, and oil spill emergency response. Finally, the paper points out current deficiencies and future directions of the potential technique. [ABSTRACT FROM AUTHOR]

Abstract Al-Ahlam Sea Resort is located at km 92 of International Coastal Road on the Northwest Coast of Egypt. Coastal projects, such as shore-parallel breakwaters cause man-induced coastal changes. Consequently, the stages of their implementation almost affect the shoreline changes and sedimentation in the area. Hence, many problems associated with these structures induce beach erosion on down-drift side which may extend beyond the project area. The study objectives are to evaluate factors inducing the problems, assess the impact of the delay of construction phases of the breakwater on the bay and shoreline, and estimate the economic and environmental losses, hence proposing immediate and permanent appropriate measures. These have been achieved based on analyses of shoreline changes, sea level variations, waves and marine survey during the period between 2008 and 2015. The implementation plan of the submerged breakwater project was scheduled to start on 2010 and end on 2012, ignoring the periods of extreme waves, storms and summer swells. Due to difficulties facing the execution company in work in the project area during the last five years, the project is still under implementation and only about 60% of its recommended works has been achieved. The present study defines the existing conditions prevailing the project area and changes that have been instigated due to delay in the project execution schedule using field data and marine surveys performed during the period between 2010 and 2015. The study revealed that the area was subjected to sever erosion in the eastern zone and its adjacent area led to a loss in beach sand reached to 45000 m3. Besides, in the western side, sedimentation is prevailing due to the constructed artificial lagoon used for maintenance operations of the implementation marine equipment. This sedimentation leads to difficulties in the entry and departure to and from the lagoon. The study indicated that the delay of the implementation of the breakwater caused shoreline and morphology changes. These led to economic and environmental losses exceeds 2.0 million USD about 30% of the estimated original cost. The study recommended immediate start-up dredging works in the western zone and the middle sector of the project area to facilitate the maneuvering of the marine equipment, which can speed up the implementation process in order to finalize the execution of the breakwater and to reduce the economic and environmental losses. The equilibrium of the shoreline and the bay in case of completion of the submerged breakwater has been checked by application of MIKE 21 Numerical Model. [ABSTRACT FROM AUTHOR]

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Private industry, the Government of Gabon and two international NGOs collaborated to conduct marine surveys off the coast of Gabon, Central Africa. Surveys addressed multiple objectives of surveillance and monitoring, the documentation of the distribution of and threats to the marine megafauna, and capacity-building among government agents and local early-career scientists. During 22 days of survey effort over a two-year period, observers documented humpback whalesMegaptera novaeangliae, bottlenose dolphinsTursiops truncatus, Atlantic humpback dolphinsSousa teusziiand common dolphinsDelphinus delphis. Humpback whale presence was limited to the months of July to November. Bottlenose dolphins were present year-round and photo-identification of individuals indicated a closed, resident population, with an abundance estimate of 118 (CV = 21.6%, 95% CI 78–180). Small open-decked fishing vessels with gillnets were observed concentrated around river mouths within 2 km of shore, while commercial trawlers were at least 10 km offshore; all were confirmed to be registered and legal. Observations of marine turtles, flocks of marine birds, and floating logs and other debris were sparse. This multi-stakeholder collaboration to conduct a marine survey can serve as an effective model by which funding and logistic support from private industry paired with technical expertise from NGOs and academic institutions can benefit marine and coastal conservation. [ABSTRACT FROM PUBLISHER]

Historically, marine ecologists have lacked efficient tools that are capable of capturing detailed species distribution data over large areas. Emerging technologies such as high-resolution imaging and associated machine-learning image-scoring software are providing new tools to map species over large areas in the ocean. Here, we combine a novel diver propulsion vehicle ( DPV) imaging system with free-to-use machine-learning software to semi-automatically generate dense and widespread abundance records of a habitat-forming algae over ~5,000 m2 of temperate reef. We employ replicable spatial techniques to test the effectiveness of traditional diver-based sampling, and better understand the distribution and spatial arrangement of one key algal species. We found that the effectiveness of a traditional survey depended on the level of spatial structuring, and generally 10-20 transects (50 × 1 m) were required to obtain reliable results. This represents 2-20 times greater replication than have been collected in previous studies. Furthermore, we demonstrate the usefulness of fine-resolution distribution modeling for understanding patterns in canopy algae cover at multiple spatial scales, and discuss applications to other marine habitats. Our analyses demonstrate that semi-automated methods of data gathering and processing provide more accurate results than traditional methods for describing habitat structure at seascape scales, and therefore represent vastly improved techniques for understanding and managing marine seascapes. [ABSTRACT FROM AUTHOR]

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To date there is one proven hydrocarbon accumulation on the Ashmore Platform, Bonaparte Basin, Australia, with hydrocarbon charge remaining a key exploration risk. To the south, the neighbouring Browse Basin has proven lateral migration of generated hydrocarbons to the basin bounding highs, as evidenced by seeps located on the Yampi Shelf. This paper describes the findings of a natural seeps study carried out to establish if migrating subsurface hydrocarbons reach the southern flanks of the Ashmore Platform basement high. The integrated study combined remote sensing, geophysical, acoustic, photographic and geochemical techniques and has identified three areas of seepage; one area characteristic of persistent seepage and two areas of interpreted episodic leakage. Geochemical data collected from samples at one of these sites demonstrates the presence of thermogenic liquid hydrocarbons, with isotopic compositions falling within the range of values exhibited by oils sourced by the Lower Cretaceous Echuca Shoals Formation. The identification of active natural seepage along the southern flank of the Ashmore Platform provides evidence that hydrocarbons generated within the Caswell Sub-basin are able to laterally migrate onto the flanks of the Ashmore Platform structural high. As such, these findings reduce charge risk for the Ashmore Platform and regional exploration risks in the northern Browse Basin. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to present a system developed for detection andaccurate mapping of ferro-metallic objects buried below the seabed in shallow waters. Thesystem comprises a precise magnetic gradiometer and navigation subsystem, both installedon a non-magnetic catamaran towed by a low-magnetic interfering boat. In addition wepresent the results of a marine survey of a near-shore area in the vicinity of Atlit, a townsituated on the Mediterranean coast of Israel, about 15 km south of Haifa. The primarypurpose of the survey was to search for a Harvard airplane that crashed into the sea in 1960.A magnetic map of the survey area (3.5 km2 on a 0.5 m grid) was created revealing theanomalies at sub-meter accuracy. For each investigated target location a correspondingferro-metallic item was dug out, one of which turned to be very similar to a part of thecrashed airplane. The accuracy of location was confirmed by matching the position of theactual dug artifacts with the magnetic map within a range of ± 1 m, in a water depth of 9 m.

Copyright of Hydrographic Surveying & Charting / Haiyang Cehui is the property of Hydrographic Surveying & Charting Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Hydrographic Surveying & Charting / Haiyang Cehui is the property of Hydrographic Surveying & Charting Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Autonomous recognition of marine targets is considered a promising technology for autonomous underwater vehicle (AUV) marine survey, and AUV equipped with side-scan sonar (SSS) for recognition is the key to surveys. As a fundamental function, SSS recognition remains unsolved due to the challenging image conditions of SSS and insufficient algorithm robustness. This paper proposes an accurate and real-time dual-branch recognition framework containing segmentation and refinement branches. Firstly, the segmentation branch uses a lightweight learning network to analyze the data comprehensively. In this branch, we propose a densely connected local attention recurrent residual (LAR2) block as the backbone, and at the same time, an atrous convolution is introduced. This branch can focus on the features of interest in the image, ensuring better feature representation with low-resolution SSS information while guiding the next branch. Secondly, the refinement branch is to adjust the previous branch's results and combines the low-level and high-level features. We propose holistic attention (HA) block in this branch, which can further improve the target recognition performance. Finally, we adopt the feature fusion method of bilinear pooling to integrate the results of the two branches to output a high-precision recognition image. In offline experiments and sea trials, our proposed method outperforms other competing algorithms in the four indicators of semantic segmentation, and achieves a computation speed of 92.66 ms (± 0.86 ms) per image on AUV dedicated hardware. The method has strong robustness, meets real-time performance, and can be widely used in AUV marine survey. • A dual-branch framework is proposed for the AUV marine survey. • The framework has the characteristics of autonomy, real-time and high precision. • Experiments are carried out to prove the universality and robustness of the framework. • Potential engineering application areas of the framework are analyzed. [ABSTRACT FROM AUTHOR]

Abstract: The paper illustrates some marine survey AUVs plus their features and typical configurations, and analyzes their key technologies through classification and analysis, which are currently existed or under development. Their composition can be divided into basic modules and functional modules. Basic modules include central processing system, propeller system, power supply system and navigation system etc. Meanwhile, functional modules refer to auxiliary sensor and survey equipment. As for AUV applied in marine survey, designer should pay more consideration to the running state in high velocity flow and strengthen the control of side thrust. The configurations of marine survey AUVs from companies like Kongsberg in Norway, Hydroid in U.S., Bluefin Robotics in U.S. and Hafmynd in Iceland are analyzed and classified. The research and development process of domestic AUV are also be reviewed. As AUV can collect data with highly efficiency and better quality, it will replace traditional means of surface vessels with towed systems for its portability. Easy use of AUV can significantly reduce fuel consumption of ships, which will be widely used in marine survey in the future as a cost-effective method. [Copyright &y& Elsevier]

The Benthic Ecological Assessment for Marginal Reefs (BEAMR) method is a universal assessment procedure which helps to quantify the ''health'' condition of a coral reef habitat over time. Coral reefs, due to their complexity as an ecosystem, have presented problems in the past to marine researchers trying to assess the performance of the habitat through statistical evaluation. Previous methodologies such as the Atlantic and Gulf Rapid Reef Assessment method and the Caribbean Coastal Marine Productivity Program, while being useful, were created specifically for reefs within the Caribbean Sea and are biased toward one or two main indicator organisms (e.g., stony corals). However, given that most reefs worldwide are considered marginal habitats, which describes them as having an impoverished community condition with biogeographic limits, the BEAMR method offers a more comprehensive analysis of all benthic functional groups defining the reef. Assessments and analysis using the BEAMR method provide marine researchers with accurate in situ documentation of all aspects within benthic coral communities, allowing conservation managers to more effectively protect these marine habitats. Coral reef resources are under a constant threat from both human and natural forces, making habitat assessment protocols, such as the BEAMR method, an important tool in the worldwide conservation of coral reef communities. [ABSTRACT FROM AUTHOR]

Deception Island is a young, active volcano located in the south-western part of Bransfield Strait, between the Antarctic Peninsula and the South Shetland archipelago. New gravity and magnetic data, from a marine geophysical cruise (DEC VOL-99), were analysed. Forty-eight survey lines were processed and mapped around Deception Island to obtain Bouguer and magnetic anomaly maps. These maps show well-defined groups of gravity and magnetic anomalies, as well as their gradients. To constrain the upper crustal structure, we have performed 2+1/2D forward modelling on three profiles perpendicular to the main anomalies of the area, and taking into account previously published seismic information. From the gravity and magnetic models, two types of crust were identified. These were interpreted as continental crust (located north of Deception Island) and more basic crust (south of Deception Island). The transition between these crustal types is evident in the Bouguer anomaly map as a high gradient area trending NE-SW. Both magnetic and gravity data show a wide minimum at the eastern part of Deception Island, which suggests a very low bulk susceptibility and low density intrusive body. With historical recorded eruptions and thermal and fumarolic fields, we interpret this anomaly as a partially melted intrusive body. Its top has been estimated to be at 1.7 km depth using Euler deconvolution techniques. [ABSTRACT FROM AUTHOR]

The processing of Chirp data is limited by the usual recording of the signal envelope, which enhances its immediate visibility but prevents applying methods based on wave equations. This is normally not the case for Boomer data. However, both systems are monochannel instruments, which cannot estimate properly the propagation velocity of the signal in the rocks. In this paper, we present two theorems: the first one links the Chirp or Boomer source spectrum with an expected amplitude decay curve; the second one defines conditions for the deconvolution stability of the enveloped Boomer signal when the full waveform of the source signal is known. In this way, we can jointly process and integrate heterogeneous surveys including both data types. We validated the proposed algorithms by applying them to synthetic and real data. The presented tools can improve the image resolution and the characterization of geological formations in marine surveys by reflectivity anomalies, which are distorted by standard equalization methods. [ABSTRACT FROM AUTHOR]

Wang, H.; Chen, S.H., and Luo, L., 2020. Topological characterization and optimization design for general arrangements of the research vessels. In: Bai, X. and Zhou, H. (eds.), Advances in Water Resources, Environmental Protection, and Sustainable Development. Journal of Coastal Research, Special Issue No. 115, pp. 391-395. Coconut Creek (Florida), ISSN 0749-0208. A research vessel is a special ship designed to conduct the surveys and experiments of marine hydrology, geology, meteorology, and biology. Research vessels are equipped with many laboratories and experimental instruments required by various scientific researches, such as physics, chemistry, biology, etc. Hence, the general arrangement design of the research vessels is a complex task. Current approaches to this design problem are the repetitive process of trial-and-error and rely heavily on the design experience and inspiration of ship designers. This process is time and resource-intensive, which limits the discovery of optimal arrangements and increases the design costs and time. This paper presents a novel topology optimization design approach for the general design of research vessels. In the proposed approach, a multiscale network is utilized for characterizing the general arrangements. And, a mapping from the geometric arrangement to the topological network is defined. Besides, the meta-heuristic optimization techniques are applied in the design phases. For verifying the validity, the topology optimization design approach is demonstrated on the general arrangement design of the noted research vessel Atlantis. [ABSTRACT FROM AUTHOR]