Interferometric Sidescan Sonar Research Articles

Possibility of diagnostics of layered media with interferometric side-view sonar

A method is considered and an algorithm is developed that makes it possible to identify the layered structure of the propagation medium of a probing signal based on strip survey data from an interferometric side-scan sonar (ISSS) with antennas located in a vertical plane. Using the example of mathematical modeling of phase-difference measurements of ISSS for multilayer scattering planes, the capabilities of the proposed algorithm to determine their spatial position are demonstrated in the wave propagation medium. An analysis of the accuracy of calculating the position of scattering layers at heights (depths) and with different slopes was performed. The effectiveness of the method and algorithm for diagnosing the structure of layered media has been confirmed. The effectiveness of the method was tested on experimental data obtained using ISSS.

Moats & comets - A methodology to explore for submerged prehistory at sea floor erosional features formed at artificial reefs, Atlantic continental shelf, GeorgiaUSA.

Our primary objective is to demonstrate a method that uses marine processes, principally seafloor scour, to broadly expose prehistoric landforms and associated localities. Too often, the loss of prehistoric strata to scour processes such as ravinement during broad-scale, continental shelf transgressions, are decried without the recognition of the potential for erosion at the local scale can expose those same strata for systematic study. The analysis of sea floor erosional features formed around artificial reefs by turbulent flows in the Georgia Bight have used interferometric side-scan sonar (SSS), Remotely Operated Vehicles (ROVs), ultra-high-definition videography (UHD), and sedimentological, palynological, paleontological, archaeological analytical techniques. These techniques were integrated within a geoarchaeological methodology focused on exploring the Continental Shelf for preserved evidence of prehistoric landforms, flora and fauna once thereon. A stepwise protocol was developed to first gather interferometric side-scan sonar data to be then processed by commercial software packages such as HYPACK Hydrographic and HYSWEEP together with HYSCAN and SONAR Wiz software. The sonar mosaics were imported to ArcGIS/QGIS software to characterize scour features/targets around artificial reefs that had exposed paleo-land surfaces previously obscured by the modern palimpsest sand sheet. Analysis of scours and depressions - “moats and comets” - adjacent to reef structures were evaluated using the profile tool within the HYPACK-HYSWEEP editor package. Symbology for the bathymetric raster layers was edited to provide a clear contrast and measurement at scour features. Measured GIS images were then classified as to scour extent and depth with respect to prevailing current directions responsible for producing turbulence. A ranking of the artificial reefs by factors such as scour depth and extent was used to guide subsequent investigation by ROVs. Sediment cores and grab samples were collected, and those samples underwent particle size analysis (PSA), macro-and micro-botanical analyses. All data – geophysical, GIS, video and geological – were collated and synthesized to produce an assessment of the potential of sea floor scour features to expose previously buried geomorphological/geological, paleontological and/or archaeological features of interest.

The Ability to Detect Sound Scattering Layers by Interferometric Side-Scan Sonar

The Ability to Detect Sound Scattering Layers by Interferometric Side-Scan Sonar

The Ability to Detect Sound Scattering Layers by Interferometric Side-Scan Sonar

A method and algorithm for remote detection of sound-scattering layers in the seas and oceans using strip survey data of the bottom topography by interferometric side-scan sonar (ISSS) is considered. Based on mathematical modeling of phase-difference measurements of ISSS for multilayer scattering planes in seawater, we demonstrate the possibility of detecting sound-scattering layers and measuring their depths using the proposed algorithm. The accuracy of calculating the depths of sound-dispersing layers at a constant value of the sound velocity has been evaluated and the requirements to the ISSS have been determined to ensure the necessary accuracy of detection of individual layers located at different depths. The efficiency of the proposed method is demonstrated based on the example of processing by the developed algorithm of the experimental data obtained during bottom relief studies with an 85 kHz range ISSS.

Калибровка интерферометрического гидролокатора бокового обзора по данным съемки на участке дна с известным рельефом

The paper considers algorithms for calculating the parameters of the interferometric side scan sonar based on the processing of acoustic survey data of the seabed surface with a known relief. The algorithms were tested on mathematical models of signals reflected from a flat horizontal surface. The possibilities of the proposed algorithms are demonstrated on experimental phase-difference measurements of interferometric side scan sonar obtained on a site with a flat seabed. The effectiveness of algorithms for calibration of interferometric side scan sonars is shown.

Assessment of the Kuybyshev Reservoir bed state: a case study

The generalized results of the Kuybyshev Reservoir bed relief survey using modern methods are presented on the example of two sites. Sakony site area is located on the low left bank of the Kuybyshev Reservoir in the place of sand and gravel mix extraction, Sviyazhsk site – around the cultural heritage object Sviyazhsk island-town. The change in the bottom topography was monitored using the Interferometric Side-Scan Sonar and the HyScan software. Bathymetric maps and transverse profiles for study sites were built. A description of the bottom relief in the studied areas is given. As a result, reservoir bottom survey technique was developed to update its morphometry, possibility of obtained data application is discussed.

Methods to Increase the Accuracy of Calculation of the Phase Difference of Signals of an Interferometric Side-Scan Sonar

Methods to Increase the Accuracy of Calculation of the Phase Difference of Signals of an Interferometric Side-Scan Sonar

Effect of Decorrelation Factors on the Error in Measuring the Signal Phase Difference with Interferometric Systems

Based on the general model of signals scattered by the rough surface of the seabed, relations are developed for estimating the errors of measurement by the interferometric side-scan sonar (ISSS) of the arrival angles of echo signals caused by the decorrelation of the probing signals with a large base in the receiving channels due to the spatial separation of the antennas. The obtained relations allow us to adjust the signal processing algorithms received by the multiantenna interferometer to reduce the influence of additive noise on the accuracy of the measurements of the angles of arrival of echo signals.

Fusion of Swath Bathymetric Data: Application to AUV Rapid Environment Assessment

Building an accurate and large digital terrain model (DTM) of the seabed is a key issue in various applications, especially for covert rapid environment assessment using autonomous underwater vehicles (AUVs). New AUV generations are capable of acquiring bathymetry with multiple acoustic sensors: single-beam echosounder, Doppler velocity log, multibeam echosounder (MBES), interferometric sidescan sonar (ISSS), etc. As these sensors acquire the seabed with different geometries, they can be combined to produce a DTM in shorter time. For example, ISSS can reach a wide swath in shallow water but it shows an information gap at nadir, which is usually covered by completing an additional track. Simultaneously using the MBES to acquire the nadir removes the need for this additional track and reduces the energy consumption of the whole survey. This paper focuses on fusion algorithms to extract best information of the two sensors (MBES and ISSS) to feed DTM production software with optimal bathymetric information. This problem may be solved by taking into account the average information of the two sensors. However, the sensors do not always give accurate information and the average information therefore becomes biased. Another way to tackle the problem is to select a priori information given by the better of the two sensors based on a given geometric parameter (e.g., grazing angle). In this case, when the assumed best sensor fails, the information produced by the second sensor cannot be used to compensate for the erroneous information. Our approach consists in using all the available information and fuses it ahead of producing the DTM. Based on the theory of belief functions, this paper presents a framework to fuse the information coming from the two swath bathymetric sensors (MBES and ISSS). The belief theory, applied successfully to other fields, has been extended to handle the bathymetric information. The reliability and the uncertainty of each sonar are introduced in the fusion process to improve the estimation and the accuracy of the final terrain model. First, simulated sonar data, with perfectly known ground truth, are used to quantitatively assess the performance of the fusion process by comparing DTM obtained with and without fusion. Then, the experimental validation is conducted on actual data, acquired simultaneously by the two sonars systems (Klein K5000 ISSS, Reson 8125 MBES) mounted on the DAURADE AUV. Our evaluation of the fusion method shows significant quantitative and qualitative improvement in the production of the final DTM.

Methods of sonar signal processing to solve the sensing bottom surface problem

The paper deals with the processing of hydroacoustic data recorded with help of hydroacoustic research complexes. Particular attention to classic and interferometric sonars is paid. In accordance to the regulatory documentation, the minimum permissible measurement errors for the formation of bottom surface maps for various economic sectors are determined. As one of the important problems affecting the effectiveness of survey work with sonar complexes, the authors determine the problem of primary data compression, which, as a rule, leads to information loss without the possibility of its recovery. These drawbacks of the methods of primary information compression-recovery and processing of hydroacoustic data used in complexes reduce the overall effectiveness of the complexes usage both with the use of sidescan sonar and with the use of an interferometric side-scan sonar. In the framework of a numerical experiment, it has been shown that the use of chirp signals as probing pulses makes it possible to effectively apply the complex in the survey sonar mode. The results of the numerical experiment for estimating the spatial position of the object at the bottom of the sonar images using the phase difference information of the received signals using an interferometric sonar are presented. Based on the results of the experiment, the requirements for recording quality of reflected signals of various types in interferometric side-scan sonar are determined. A method of resolving the reflected (with partial overlap and overlay) hydroacoustic tones, based on the method of dividing the spectra is proposed by the authors. To improve the efficiency of the chirp signal processing, the authors suggest to improve the accuracy of the detection of the signal detection time due to the phase correction calculated through the slope of the frequency change rate of the chirp signal.

Automatic Detection of Marine Gas Seeps Using an Interferometric Sidescan Sonar

There is a significant need for reliable, cost-effective, and preferably automatic methods for detecting and monitoring marine gas seeps. Seeps at the seafloor may originate from natural sources including sediments releasing biogenic methane and volcanoes releasing CO2, or from man-made constructions such as pipelines or well heads, and potentially also from subseafloor CO2 storage sites. Improved seep detection makes it possible to estimate the amount of greenhouse gases entering the oceans, and to promptly detect and address potential leaks to reduce environmental and economical consequences. Sonar is an excellent tool for seep detection due to the strong acoustic backscatter properties of gas-filled bubbles in water. Existing methods for acoustic seep detection include multibeam and sidescan surveying, as well as active and passive sensors mounted on a stationary platform. In this work, we develop a new method for automatic seep detection using an interferometric sidescan sonar. We apply signal processing techniques combined with knowledge about acoustical and spatial properties of seeps for improved detectability. The proposed method fills an important gap in existing technology—the ability to automatically detect a seep during a single pass with an autonomous underwater vehicle (AUV) equipped with an interferometric sidescan sonar. Results from simulations as well as field data from two leaking abandoned wells in the North Sea indicate that small seeps are consistently detected on a sandy seafloor even when the observation time is limited (a single pass with the AUV). We explore the detection capability for different seafloor types ranging from silt to gravel.

Possible manifestations of underwater mud volcanoes based on results of sonar investigations in region of Taman Peninsula

This paper presents the results of three-dimensional acoustic seabed mapping in the region of the Taman Peninsula in the Black Sea using an interferometric side-scan sonar and an acoustic profiler. Mapping has revealed underwater objects identified as manifestations of underwater mud volcanism. Detailed analysis of sonar images of the relief and seabed profiles in the region of the objects has confirmed the original hypothesis.

Three-dimensional mapping of red stingray (Dasyatis akajei) movement with reference to bottom topography

Most demersal fishes maintain strong relations with bottom substrates and bottom depths and/or topography during their lives. It is important to know these relations to for understand their lives. In Tokyo Bay, red stingray, Dasyatis akajei, classified as near-threatened species by IUCN, has increased since the 1980s. It is a top predator and engages in ecosystem engineer by mixing the sand bed surface through burring behavior, and greatly influences a coastal ecosystem. It is reported that this species invades in plage and tidal flats and has sometimes injured beachgoers and people gathering clams in Tokyo bay. Thus, it is necessary to know its behavior and habitat use to avoid accidents and to better conserve the biodiversity of ecosystems. However, previous studies have not examined its relationship with the bottom environment. This study aims to describe its behavior in relation to the bottom environment. We sounded three dimensional bottom topography of their habitat off Kaneda Cove in Tokyo Bay with interferometric sidescan sonar system and traced the movement of red stingrays by attaching a data logger system to survey their migration. The results revealed that red stingray repeated vertical movement between the surface and bottom, and used not only sand beds but also rocky beds.

A method for synthesizing 3D images of the ocean bottom from interferometric side scan sonar

A method for synthesizing 3D images of scanned objects based on the output data of bathymetric and amplitude channels obtained from intereferometric side scan sonar is discussed.

IZANAGI ocean floor imaging surveys around Japan

Since 1989 the Ocean Research Institute at the University of Tokyo has started deep sea floor imaging surveys around Japan by using IZANAGI, which was developed by cooperation between the Ocean Research Institute, the University of Tokyo and Seafloor Surveys International, Inc. It is characterized by an interferometric sidescan sonar, towed at a shallow depth, typically 100 m below the sea surface at a speed of up to 10 kn (5 m/s). Two sets of transducer arrays are mounted on each side of the tow fish, transmitting 11 kHz on the starboard side and 12 kHz on the port side. They operate simultaneously at transmitting, but individually at receiving. The range of swath width can be varied from 20- to 1 km. A sidescan image is composed of 1024 pixels per one side of the swath; thus for a 10-km swath each pixel has a constant width of 5 m. Total coverage of our surveys is, so far, approximately 100 000 km2 from various geotectonic areas in the seas around Japan. The main objective of our surveys is to clarify detailed ocean floor topography which represents slope failure, active faults related to large earthquakes in the deep sea, sedimentary structure related to surface sediments transportation, and submarine volcanoes.