Scan Sonar Research Articles

Mapping the underside of an iceberg with a modified underwater glider

AbstractIcebergs pose many challenges to offshore operations in the Arctic Ocean and sub‐arctic regions. They could damage underwater infrastructure such as pipelines, and disrupt marine transportation. The below‐water shape of an iceberg is a key factor for iceberg management in the North Atlantic Ocean because it affects the iceberg towing plans and iceberg drift patterns. In recent years, unmanned platforms have been proposed as potential candidates for underwater iceberg mapping. Compared to a conventional ship‐based iceberg survey, using unmanned platforms is more efficient and safer. In this paper, we present research using a hybrid underwater glider to measure the underwater shape of an iceberg. The vehicle is equipped with a mechanical scanning sonar for range sensing and iceberg mapping, and a guidance system is designed to use the sonar measurements for guiding the vehicle to circumnavigate an iceberg at the desired standoff distance. Several field experiments have been conducted on an iceberg to evaluate the system performance. With repeated observations, the underside of the target iceberg was successfully reconstructed, and iceberg shape comparisons are presented.

BATHYMETRIC SURVEYING IN LAKE SUPERIOR: 3D MODELING AND SONAR EQUIPMENTS COMPARING

Abstract. This paper represents the overview of hydrographic surveying and different types of modern and traditional surveying equipment, and data acquisition using the traditional single beam sonar system and a modern fully autonomous underwater vehicle (AUV) IVER3. During the study, the data sets were collected using the vehicles of the Great Lake Research Center at Michigan Technological University. This paper presents how to process and edit the bathymetric data on SonarWiz5. Lastly, it compares the accuracy of the two different sonar systems in the different missions and creates 3D models to display and understand the elevations changes. Moreover, the 3D models were created after importing the data sets in the same coordinate system. In this study, the data sets were recorded by two different sensors in the two study locations in the Keweenaw Waterway in Michigan, U.S. between the cities of Houghton and Hancock. The first one equipment is the Lowrance HDS-7 sonar on the surveying boat, and other one is the EdgeTech 2205 sonar on the fully AUV of IVER3. One of the purposes of this study is to explore the sonar post processing programs, which are very important to interpret sonar and bathymetric data, and obtained the same coordinate system of the study areas. During the project, three main processing programs were used. The first one is UnderSee Explorer 2.6, which has been used to process the data sets of Polar SV boat. Secondly, EdgeTech Discover 4600 bathymetric software used EdgeTech 2205 sonar data sets to create bathymetric files that were used in SonarWiz5. Lastly, SonarWiz5 sonar processing software can be used to process the data sets. After the data acquisition and the data process, six profiles from the first study area and the five profiles from the second study are created to compare the data sets and elevations difference. It is shown that single beam sonar might miss some details, such as pipeline and quick elevation changes on seabed when we compare to the side scan sonar of IVER3 because the single side scan sonar can acquire better resolutions to understand the 3D features, such as pipelines, reliefs etc.

Mapping Posidonia oceanica (Linnaeus) Meadows in the Eastern Aegean Sea Coastal Areas of Turkey: Evaluation of Habitat Maps Produced Using the Acoustic Ground Discrimination Systems

Coastal areas include highly complex ecosystems that encompass many different and productive resources worldwide. Although having such great importance, the lack of basic knowledge concerning the marine habitat distribution and biodiversity along the Turkish shoreline is an undeniable reality. In this study, seagrass beds in the bays along the Eastern Aegean Sea coast were located and mapped. Traditionally, sea-truth data used for satellite-image and other analysis are collected through direct observations requiring scuba divers or by aquatic video-camera observation. This study included a combination of acoustic technology, video recording and interpretation, geomorphological, oceanographic, and sedimentological evaluation in order to make significant contributions of current technology. The classification of the evaluated SBP records exhibited their high discrimination capacity between different sea-bed features, making them appropriate for ground distinction. Linking of the SBP data sets to the SSS records (object-based analysis) provide to full coverage, high resolution benthic habitat maps. For this purpose, Side Scan Sonar, 3.5/10 kHz Subbottom Profiler and ADCP data were collected to a range of 50 m water depth, the data was recorded for a total 1600 km2 coastal area that consists of approximately a total 3000 km long and 1km wide grid system for Edremit, Çandarlı, Gülbahçe, Ildır, Güllük and Gökova Bays. In the study area, it was determined that the seagrasses are under danger where high human influence is located. Dense distribution of invasive plants (Caulerpa cylindracea, Stypopodium schimperi) were seen at the southern and northern part of the study area subjected to human activities.

Detection of Boulders in Side Scan Sonar Mosaics by a Neural Network

Boulders provide ecologically important hard grounds in shelf seas, and form protected habitats under the European Habitats Directive. Boulders on the seafloor can usually be recognized in backscatter mosaics due to a characteristic pattern of high backscatter intensity followed by an acoustic shadow. The manual identification of boulders on mosaics is tedious and subjective, and thus could benefit from automation. In this study, we train an object detection framework, RetinaNet, based on a neural network backbone, ResNet, to detect boulders in backscatter mosaics derived from a sidescan-sonar operating at 384 kHz. A training dataset comprising 4617 boulders and 2005 negative examples similar to boulders was used to train RetinaNet. The trained model was applied to a test area located in the Kriegers Flak area (Baltic Sea), and the results compared to mosaic interpretation by expert analysis. Some misclassification of water column noise and boundaries of artificial plough marks occurs, but the results of the trained model are comparable to the human interpretation. While the trained model correctly identified a higher number of boulders, the human interpreter had an advantage at recognizing smaller objects comprising a bounding box of less than 7 × 7 pixels. Almost identical performance between the best model and expert analysis was found when classifying boulder density into three classes (0, 1–5, more than 5) over 10,000 m2 areas, with the best performing model reaching an agreement with the human interpretation of 90%.

Comparative study between acoustic signals and images for detecting seabed features

This study aims to provide a recent seabed characteristic of ridges along the eastern coast of Alexandria on the Egyptian Mediterranean Sea. Side scan sonar was used for acoustic imaging and Quester Tangent Corporation (QTC) VIEW for acoustic signal survey. ROV was applied to detailed video survey and sediment sampling to provide ground truth data. The integration between acoustic signal classes and the acoustic images can divided the study area into three acoustic categories; 1) weak backscatter corresponds to very fine sand to silt sediments, 2) strong backscatter confined to coarse to medium sand, and 3) isolated reflections, which appear widespread along the whole study area and represent two discrete parallel discontinuous hard limestone ridges. These discrete parallel ridges are found to be trending parallel to the coastline. A seabed feature map for the study area is obtained from the integration of output results of side scan sonar backscatter analysis with the QTC acoustic classification and ground-truthing using ROV and grab sampler. The high resolution of acoustic image help to detect the variation of the wavelength and amplitude of sand ripples in the study area.

Generating cognitive maps using echo features from a biomimetic audible sonar.

A sonar cognitive map displays target components that are specified by signal features extracted from a single binaural echo pair. A biomimetic audible sonar probes targets configured using posts connected by tangential planes. Echo envelopes are processed to extract values of eight parameters that govern the mapping process. Being tuned to recognize posts and planes, a cognitive map is composed of these two components using the posts' centers and radii as landmarks. A platform with translational and rotational degrees of freedom implements a landmark-centric scanning trajectory whose step size adaptively changes with echo information. The sonar tracks the target surface by maintaining a constant first-echo arrival time and by equalizing binaural echo times to form singular echoes that identify landmarks. The mapping process employs five states from detection to termination that pass through the singular echo state. Separate states process echo interference caused by two posts and echoes from planar surfaces. Sonar scanning stops when the current landmark parameters match those of the first landmark. Two targets configured with three posts and an added plane illustrate the procedure. Cognitive maps exhibit landmark locations that are accurate to ±5% with post radius estimates accurate to ±20%.

스캐닝 소나 시스템을 이용한 수중구조물의 2차원 및 3차원 매핑

스캐닝 소나 시스템을 이용한 수중구조물의 2차원 및 3차원 매핑

Evaluation of underwater acoustic images obtained by the early stage monotone pulse-echo Synthetic Aperture Sonar

Synthetic Aperture Sonar (SAS) is a side-looking underwater acoustic imaging sonar that can obtain higher resolution images than those by the conventional Side Scan Sonar (SSS). Due to its high resolution images, it can be applied to various fields of studies from military to civilian purposes. Republic of Korea recently has launched a research project developing the prototypes of SAS being operated in a few hundreds kHz of acoustic signals. This project adopted the towfish as the SAS platform that are to be towed under a few tens of water depth, which has a price advantage over Autonomous Underwater Vehicle (AUV), but gives unstable motion. It also adopted the monotone pulse-echo mode as transceiver method of the prototypes that gives relatively simpler implementation of the data acquisition module although it gives inferior SNR to the chirp mode. In the current study, the underwater acoustic images of the protype SAS taken both in the fresh water and offshore of Korea are to be shown. Current study also...

Automatic Bluefin Tuna (Thunnus thynnus) biomass estimation during transfers using acoustic and computer vision techniques

In this work, acoustic and computer vision techniques are combined to develop an automatic procedure for biomass estimation of tuna during transfers. A side scan sonar working at 200 kHz and a stereo camera, positioned facing towards the surface to record the ventral aspect of fish, are set as acquisition equipment. Moreover, a floating structure has been devised to place the sensors between cages in transfers, creating a transfer canal that allows data acquisition while fish swim from donor to receiving cage. Biomass assessment is computed by counting transferred tuna and sizing a representative sample of the stock. The number of transferred tuna is automatically deduced from acoustic echograms by means of image processing techniques, whereas tuna size is computed from the stereo videos using our automatic computer vision procedure based on a deformable model of the fish ventral silhouette. The results show that the system achieves automatic tuna counting with error below 10%, achieving around 1% error in the best configuration, and automatic tuna sizing of more than 20% of the stock, with highly accurate Snout Fork Length estimation when compared to true data from harvests. These results fulfil the requirements imposed by International Commission for the Conservation of Atlantic Tunas for compliant transfer operations.

Ice-Gouging Topography of the Exposed Aral Sea Bed

Ice gouging, or scouring, i.e., ice impact on the seabed, is a well-studied phenomenon in high-latitude seas. In the mid-latitudes, it remains one of the major geomorphic processes in freezing seas and large lakes. Research efforts concerning its patterns, drivers and intensity are scarce, and include aerial and geophysical studies of ice scours in the Northern Caspian Sea. This study aims to explain the origin of the recently discovered linear landforms on the exposed former Aral Sea bottom using remotely sensed data. We suggest that they are relict ice gouges, analogous to the modern ice scours of the Northern Caspian, Kara and other seas and lakes, previously studied by side scan sonar (SSS) surveys. Their average dimensions, from 3 to 90 m in width and from hundreds to thousands of meters in length, and spatial distribution were derived from satellite imagery interpretation and structure from motion-processing of UAV (unmanned aerial vehicle) images. Ice scouring features are virtually omnipresent at certain seabed sections, evidencing high ice gouging intensity in mid-latitude climates. Their greatest density is observed in the central part of the former East Aral Sea. The majority of contemporary ice gouges appeared during the rapid Aral Sea level fall between 1980 and the mid-1990s. Since then, the lake has almost completely drained, providing a unique opportunity for direct studies of exposed ice gouges using both in situ and remote-sensing techniques. These data could add to our current understanding of the scales and drivers of ice impact on the bottom of shallow seas and lakes.

Underwater operation of a full tensor SQUID gradiometer system

For the first time a mobile underwater full tensor magnetic gradiometer (FTMG) system based on low-Tc superconducting quantum interference devices (SQUIDs) has been deployed in order to scan the sea floor for magnetized targets. The application is mainly focused on waste deposits and unexploded ordnance (UXO), but could also include shallow geological features as well as archaeological remains. The main methods for detection and localisation of underwater UXO and waste deposits are side sonar scanning and magnetic mapping. While modern sonar scanners can achieve a very high spatial resolution and long detection range, they still have problems detecting targets under cover—for magnetic sensors a layer of non-magnetic sand or ooze does usually not have an effect on the signal apart from an increased distance. In this paper we discuss the setup of the mobile underwater FTMG SQUID system, its challenges and main performance features. It also illustrates its detection and localization capabilities in tests on known magnetic targets.

Object Detection In Underwater Acoustic Images Using Edge Based Segmentation Method

Abstract Image segmentation techniques play a vital role in partitioning the image into segments. These techniques are used for detecting the objects in the images. The real challenge in the acoustic image segmentation lies in differentiating the sea floor, sediments and the objects. Due to the typical characteristics and low resolution of the acoustic images, segmentation techniques such as region based, morphological based and edge based methods are not suitable. The sediments will also be traced along with the objects that makes the detection process a very difficult one. In this research paper, edge based segmentation method that uses the morphological operations for identifying the edges followed by a object tracing algorithm is proposed. The images used in this work are captured in real time using Edgetech 4125 Side scan sonar device. The acoustic images are first pre-processed using Wiener and Median filters and a morphological gradient is obtained by subtracting the morphologically dilated and eroded image. Next the edge map of the acoustic images are obtained using binarization method by which the object’s boundary is made visible. Finally a Moore’s object tracing algorithm is used for detecting the objects in the images.

Automated Survey in Very Shallow Water using an Unmanned Surface Vehicle

The paper describes a combined survey campaign using an unmanned surface vehicle and integrating a side scan sonar and two magnetometers in a gradiometer set-up in very shallow water of the coastal transition zone from land to water. For the survey several areas have to be covered to provide an unexploded ordnance clearance for identifying places suitable for positioning of a jack-up barge needed for a subsequent offshore drilling campaign. Next to the limited water depth the necessary small line spacing especially for the magnetometer measurements were challenging. In that way, the paper discusses the adaptation of the necessary modules for guidance, navigation and control of the vehicle to run the survey campaign with a reliable coverage of the measurement area. Therefore, methods and applications are presented used for path planning, straight line path following, sensor integration and fusion as well as vehicle motion control. Further, the paper describes the connection between the modules to establish the entire closed system. In addition, the paper gives an overview about the requirements the survey campaign and the specified instrumentation as well as the resulting vehicle set-up. Especially the unconventional installation of the magnetometers was essential for the measurements in very shallow water. The paper finishes with results of the side scan sonar and magnetometer measurements and discusses the motion control process with regard to the survey requirements.

Side Scan Sonar Image Super Resolution via Region-Selective Sparse Coding

Side scan sonar using low frequency can quickly search a wide range, but the images acquired are of low quality. The image super resolution (SR) method can mitigate this problem. The SR method typically uses sparse coding, but accurately estimating sparse coefficients incurs substantial computational costs. To reduce processing time, we propose a region-selective sparse coding based SR system that emphasizes object regions. In particular, the region that contains interesting objects is detected for side scan sonar based underwater images so that the subsequent sparse coding based SR process can be selectively applied. Effectiveness of the proposed method is verified by the reduced processing time required for image reconstruction yet preserving the same level of visual quality as conventional methods.

Sensor Fusion-based 3D Reconstruction by Two Sonar Devices for Seabed Mapping

We propose a sequential method to extract height information for 3D mapping by using sensor fusion of two sonar devices. The 3D reconstruction using sonar image from forward scanning sonar (FSS) is an ill-posed problem, thus we need additional constraints to extract 3D information from the sonar images. Our approach is to utilize complementary information from an additional sonar which is profiling sonar (PS) and geometric constraints between the installations of two sonars. Two sonars are fixed in the specialized installation, thus data from one sonar device can be converted into that of another one by using geometric constraints. The fusion process proceeds in three stages. The first stage is to carve out no object area using the occupancy grid mapping scheme. The second stage is to predict the elevation angle of the FSS by using the PS measurement and geometric constraints. The third stage is particle filtering using the generated particles by computing the weight and to collect the data of FSS. To verify the proposed method, we applied the proposed method in simulation and experiment in engineering basin with AUV.

Characterizing Lake Bottom Sediments Using Marine Geophysical Tools

Missouri is a state with rich karst terrain. Geotechnical evaluation of foundation design for bridges and dams requires an understanding of the characteristics of subsurface geological environment, including sediments, bedrock and benthic habitat. It is crucial that the community empowers itself with the knowledge of the karst system’s characteristics in order to potentially use it as a source of water and drainage, but also to avoid the disaster of building constructions too close to vulnerable land on top of massive karst caverns. Electrical resistivity tomography profiling (underwater cables), and continuous resistivity profiling (towed cable) surveys were conducted to characterize the lake sediments (rock and soil) beneath the man-made Little Prairie Lake, in Central of Missouri State, United States. Electrical resistivity (with marine cables and towed cable) was used to determine variability in the lithology and thickness of sediments (soil and rock) beneath the lake with conjunction of echo sounder in order to calculate water depth. Side scan sonar was used to map the variations in the lithology/nature of exposed lakebed sediments and to locate the potential hazard of trees. On land, electrical resistivity tomography was used with multi-channel analysis of surface wave method to determine sediments, joints, and the depth of bedrock. Analyses of the acquired data revealed the location and orientation of the original stream channels (prior to the construction of the earth fill dam). Underwater electrical resistivity tomography and continuous resistivity profiling determined joints, sediments, and bedrock underneath water bodies. Integrated marine geophysical tools help to evaluate the subsurface prior to any construction project (dam or bridge), are useful in determining the characteristics of lithology (fractured rock, intact rock and soil), and make it possible to map benthic habitat and the submerged potential hazards of trees on the lakebed as well as accurately measuring water depth.

Reclaimed artificial coastal territories for the development of urban areas

The article discusses the possibility and perspectives of using the reclaimed artificial areas in the coastal zone of marine estuaries for the sustainable development of urban infrastructure and creation of modern architectural ensembles with the background of green economy using the example of Lakhta-Center on the northern coast of the Neva Bay (St. Petersburg, Russia). The geo-ecological stability of underwater and coastal landscapes of the coastal zone of the Neva Bay is analyzed using side scan sonar. The environmental sensitivity of coastal ecosystems is estimated. The received data can be used on practice for planning the construction work and for the development of the infrastructure of urbanized coastal zone of the Neva Bay. The general geo-ecological situation in the observed area is rather stable. The coastal zone has good perspectives for the development of a sustainable urban infrastructure against the backdrop of the green economy. The special attention should be paid to migration of birds and fish, who are using the North Lakhta coast as a temporary refugium during Spring and Autumn migrations. An effective solution from both environmental and economic points of view could be the organization of the Nature Conservation Reserve, which is spatially associated with the Lakhta Center zone. Such type of the complex using of the coastal zone could be a good example of the spatial planning in the environmentally sensitive area.

Low-Altitude and High-Speed Terrain Tracking Method for Lightweight AUVs

This paper proposes a new method for cruising-type autonomous underwater vehicles (AUVs) to track rough seafloors at low altitudes while also maintaining a high surge velocity. Low altitudes are required for visual observation of the seafloor. The operation of AUVs at low altitudes and high surge velocities permits rapid seafloor imaging over a wide area. This method works without high-grade sensors, such as inertial navigation systems (INS), Doppler velocity logs (DVL), or multi-beam sonars, and it can be implemented in lightweight AUVs. The seafloor position is estimated based on a reflection intensity map defined on a vertical plane, using measurements from scanning sonar and basic sensors of depth, attitude, and surge velocity. Then, based on the potential method, a reference pitch angle is generated that allows the AUV to follow the seafloor at a constant altitude. This method was implemented in the AUV HATTORI, and a series of sea experiments were carried out to evaluate its performance. HATTORI (Highly Agile Terrain Tracker for Ocean Research and Investigation) is a lightweight and low-cost testbed designed for rapid and efficient imaging of rugged seafloors, such as those containing coral reefs. The vehicle succeeded in following a rocky terrain at an altitude of approximately 2 m with a surge velocity of approximately 0.8 m/s. This paper also presents the results of sea trials conducted at Ishigaki Island in 2017, where the vehicle succeeded in surveying the irregular, coral-covered seafloor.

Pemberdayaan Masyarakat Nongsa Dengan Pembelajaran Penentuan Daerah Penangkapan Ikan Berbasis Teknologi Dibidang Kelautan

Keterbatasan teknologi di bidang kelautan merupakan masalah besar yang dimiliki setiap daerah pesisir di Indonesia. Dengan melihat penurunan tingkat pendapatan di daerah Kota Batam dan secara keseluruhannya adalah di Pulau Batam, maka teknologi adalah jawaban untuk mengatasi permasalahan ini. Kegiatan pengabdian masyarakat ini bertujuan untuk meningkatkan pemahaman dan keterampilan masyarakat Pantai Bale-bale, Nongsa, Batam mengenai penentuan dan pemetaan daerah penangkapan ikan (DPI), hak kekayaan intelektual (Lokasi Penangkapan Ikan), serta pengembangan bahan ajar (buku ajar) di kampus Politeknik Negeri Batam. Masyarakat bermatapencaharian nelayan di Pantai Bale-bale, Nongsa, Batam ini sudah mampu mengoperasikan GPS Map 585 dan alat deteksi kedalaman instrumen Side Scan Sonar untuk mendeteksi dan menyimpan data lokasi yang terdapat banyak ikan. Berdasarkan hasil kegiatan pengabdian masyarakat tersebut, dapat disimpulkan bahwa partisipasi masyarakat di daerah Bale-Bale khususnya remaja yang mempunyai jiwa muda dan terampil, merupakan faktor kunci yang sangat menentukan keberhasilan proses pemanfaatan teknologi di bidang kelautan untuk menduga stok ikan dan membantu meningkatkan tingkat efisiensi dalam proses melaut.

Synergistic Use of UAV and USV Data and Petrographic Analyses for the Investigation of Beachrock Formations: A Case Study from Syros Island, Aegean Sea, Greece

Up until the last ten years, remote sensing data and especially high-resolution satellite data and airphotos were mainly used in shallow water mapping. The evolution and low cost of unmanned aerial vehicles (UAVs) provides a new tool for coastal area monitoring. This paper presents the synergistic use of a small commercial UAV and an unmanned surface vehicle (USV) for beachrock mapping in Syros Island, Greece. RGB images collected with a quadcopter were processed using Structure from Motion (SFM) photogrammetry in order to create digital surface models (DSMs) and orthophotos of the coastline. A beachrock lying in shallow waters was detected and mapped using the UAV derived products. At the same time, a USV equipped with a compact side scan sonar (SSS) and bathymetric sonar system, provided the shape of the beachrock by mosaicking the backscatter strength of the SSS. In order to evaluate the results of the UAV and USV data derivatives, the beachrock perimeter and its depth were also mapped using a differential global navigation satellite system (GNSS) receiver. During the fieldwork, samples from the beachrock were collected and analyzed in the laboratory. The mineralogical composition of the bulk samples was determined by powder X-ray diffraction (XRD). Further petrographic study was also performed by petrographic polarizing microscope, macroscope, and scanning electron microscopy (SEM). Beachrock samples are classified as fine to medium grain sandstones and conglomerates. The mineral compositions of their grains and lithoclasts reflect the bedrocks of Syros Island (mainly metamorphic rocks) while a micritic high-Mg calcite constitutes the cement of these rocks.