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Special Issue "Advances in Undersea Remote Sensing"

A special issue of Remote Sensing (ISSN 2072-4292). This special issue belongs to the section "Ocean Remote Sensing".

Deadline for manuscript submissions: closed (31 January 2019)

Special Issue Editor

Guest Editor
Prof. Nicholas Makris

Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
Website | E-Mail
Interests: sensing and perception; acoustics; ocean exploration; marine ecology; scattering and propagation in random media; statistical estimation; marine geophysics; musical instrument acoustics and evolution; polar and icy satellite exploration

Special Issue Information

Dear Colleagues,

Significant challenges exist for sensing in the world's oceans, which cover more than 70% of the Earth's surface. A variety of methods have been developed over the last century to explore undersea ecosystems, geophysical phenomenon and to detect submerged objects. Many of them involve the use of acoustics, but other approaches, such as the use of optics and lasers, also have been shown to have advantages in certain scenarios.

This Special Issue of Remote Sensing on "Undersea Remote Sensing" is designed to explore all aspects of remote sensing in the underwater environment, including methods and applications. For example, we would like to invite authors to submit original manuscripts on the following topics:

  • underwater sensing of marine life
  • sensing of marine geophysical features and phenomena
  • underwater ambient sounds and noise
  • underwater sensing in polar environments
  • underwater remote sensing methods, systems and instruments
  • propagation and scattering in underwater sensing
  • signal processing in underwater acoustic remote sensing
  • sensing in extraterrestrial oceans

Prof. Nicholas Makris
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Remote Sensing is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Undersea Sensing
  • Ocean Acoustics
  • Ocean Optical Sensing
  • Ocean Laser Sensing
  • Underwater Acoustics
  • Hyrdroacoustics
  • Undersea Exploration
  • Underwater Sensing

Published Papers (11 papers)

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Research

Open AccessArticle
A Comparison of Three Sediment Acoustic Models Using Bayesian Inversion and Model Selection Techniques
Remote Sens. 2019, 11(5), 562; https://doi.org/10.3390/rs11050562
Received: 15 January 2019 / Revised: 21 February 2019 / Accepted: 2 March 2019 / Published: 7 March 2019
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Abstract
Many geoacoustic models are used to establish the relationship between the physical and acoustic properties of sediments. In this work, Bayesian inversion and model selection techniques are applied to compare combinations of three geoacoustic models and corresponding scattering models—the fluid model with the [...] Read more.
Many geoacoustic models are used to establish the relationship between the physical and acoustic properties of sediments. In this work, Bayesian inversion and model selection techniques are applied to compare combinations of three geoacoustic models and corresponding scattering models—the fluid model with the effective density fluid model (EDFM), the grain-shearing elastic model with the viscosity grain-shearing (VGS(λ)) model, and the poroelastic model with the corrected and reparametrized extended Biot–Stoll (CREB) model. First, the resolution and correlation of parameters for the three models are compared based on estimates of the posterior probability distributions (PPDs), which are obtained by Bayesian inversion using the backscattering strength data. Then, model comparison and selection techniques are utilized to assess the matching degree of model predictions and measurements qualitatively and to ascertain the Bayes factors in favor of each quantitatively. These studies indicate that the fluid and poroelastic models outperform the grain-shearing elastic model, in terms of both parameter resolution and the ability to produce predictions in agreement with measurements for sandy sediments. The poroelastic model is considered to be the best, as the inversion based on it can provide more highly resolved information of sandy sediments. Finally, the attempt to implement geoacoustic inversion with different models provides a relatively feasible remote sensing scheme for various types of sediments under unknown conditions, which needs further validation. Full article
(This article belongs to the Special Issue Advances in Undersea Remote Sensing)
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Open AccessArticle
Multi-Frequency, Multi-Sonar Mapping of Shallow Habitats—Efficacy and Management Implications in the National Marine Park of Zakynthos, Greece
Remote Sens. 2019, 11(4), 461; https://doi.org/10.3390/rs11040461
Received: 22 January 2019 / Revised: 15 February 2019 / Accepted: 18 February 2019 / Published: 23 February 2019
Cited by 2 | PDF Full-text (43417 KB) | HTML Full-text | XML Full-text
Abstract
In this work, multibeam echosounder (MBES) and dual frequency sidescan sonar (SSS) data are combined to map the shallow (5–100 m) benthic habitats of the National Marine Park of Zakynthos (NMPZ), Greece, a Marine Protected Area (MPA). NMPZ hosts extensive prairies of the [...] Read more.
In this work, multibeam echosounder (MBES) and dual frequency sidescan sonar (SSS) data are combined to map the shallow (5–100 m) benthic habitats of the National Marine Park of Zakynthos (NMPZ), Greece, a Marine Protected Area (MPA). NMPZ hosts extensive prairies of the protected Mediterranean phanerogams Posidonia oceanica and Cymodocea nodosa, as well as reefs and sandbanks. Seafloor characterization is achieved using the multi-frequency acoustic backscatter of: (a) the two simultaneous frequencies of the SSS (100 and 400 kHz) and (b) the MBES (180 kHz), as well as the MBES bathymetry. Overall, these high-resolution datasets cover an area of 84 km2 with ground coverage varying from 50% to 100%. Image texture, terrain and backscatter angular response analyses are applied to the above, to extract a range of statistical features. Those have different spatial densities and so they are combined through an object-based approach based on the full-coverage 100-kHz SSS mosaic. Supervised classification is applied to data models composed of operationally meaningful combinations between the above features, reflecting single-sonar or multi-sonar mapping scenarios. Classification results are validated against a detailed expert interpretation habitat map making use of extensive ground-truth data. The relative gain of one system or one feature extraction method or another are thoroughly examined. The frequency-dependent separation of benthic habitats showcases the potentials of multi-frequency backscatter and bathymetry from different sonars, improving evidence-based interpretations of shallow benthic habitats. Full article
(This article belongs to the Special Issue Advances in Undersea Remote Sensing)
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Open AccessArticle
Modeling Microseism Generation by Inhomogeneous Ocean Surface Waves in Hurricane Bonnie Using the Non-Linear Wave Equation
Remote Sens. 2018, 10(10), 1624; https://doi.org/10.3390/rs10101624
Received: 2 July 2018 / Revised: 30 September 2018 / Accepted: 4 October 2018 / Published: 12 October 2018
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Abstract
It has been shown that hurricanes generate seismic noise, called microseisms, through the creation and non-linear interaction of ocean surface waves. Here we model microseisms generated by the spatially inhomogeneous waves of a hurricane using the non-linear wave equation where a second-order acoustic [...] Read more.
It has been shown that hurricanes generate seismic noise, called microseisms, through the creation and non-linear interaction of ocean surface waves. Here we model microseisms generated by the spatially inhomogeneous waves of a hurricane using the non-linear wave equation where a second-order acoustic field is created by first-order ocean surface wave motion. We treat range-dependent waveguide environments to account for microseisms that propagate from the deep ocean to a receiver on land. We compare estimates based on the ocean surface wave field measured in hurricane Bonnie in 1998 with seismic measurements made roughly 1000 km away in Florida. Full article
(This article belongs to the Special Issue Advances in Undersea Remote Sensing)
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Open AccessArticle
Side-Scan Sonar Image Mosaic Using Couple Feature Points with Constraint of Track Line Positions
Remote Sens. 2018, 10(6), 953; https://doi.org/10.3390/rs10060953
Received: 25 April 2018 / Revised: 1 June 2018 / Accepted: 12 June 2018 / Published: 15 June 2018
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Abstract
To obtain large-scale seabed surface image, this paper proposes a side-scan sonar (SSS) image mosaic method using couple feature points (CFPs) with constraint of track line positions. The SSS geocoded images are firstly used to form a coarsely mosaicked one and the overlapping [...] Read more.
To obtain large-scale seabed surface image, this paper proposes a side-scan sonar (SSS) image mosaic method using couple feature points (CFPs) with constraint of track line positions. The SSS geocoded images are firstly used to form a coarsely mosaicked one and the overlapping areas between adjacent strip images can be determined based on geographic information. Inside the overlapping areas, the feature point (FP) detection and registration operation are adopted for both strips. According to the detected CFPs and track line positions, an adjustment model is established to accommodate complex local distortions as well as ensure the global stability. This proposed method effectively solves the problem of target ghosting or dislocation and no accumulated errors arise in the mosaicking process. Experimental results show that the finally mosaicked image correctly reflects the object distribution, which is meaningful for understanding and interpreting seabed topography. Full article
(This article belongs to the Special Issue Advances in Undersea Remote Sensing)
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Open AccessFeature PaperArticle
Underwater Acoustic Pulsed Source Localization with a Pair of Hydrophones
Remote Sens. 2018, 10(6), 883; https://doi.org/10.3390/rs10060883
Received: 17 May 2018 / Accepted: 30 May 2018 / Published: 6 June 2018
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Abstract
A series of underwater acoustic localization experiments were conducted in the Eastern Mediterranean Sea to test the performance of a Bayesian method for localization of pulsed acoustic sources exploiting time differences between direct and surface-reflected arrivals at two hydrophones of known depth. The [...] Read more.
A series of underwater acoustic localization experiments were conducted in the Eastern Mediterranean Sea to test the performance of a Bayesian method for localization of pulsed acoustic sources exploiting time differences between direct and surface-reflected arrivals at two hydrophones of known depth. The experiments involved a controlled source (pinger) at various depths/ranges as well as vocalizing sperm whales encountered off southern Crete. The localization method provides primarily range and depth information. In addition, if the location of the hydrophones in the horizontal is known, horizontal localization can be performed as well, subject to left–right ambiguity; this was applied for whale localization. The localization results confirmed the anticipated behavior of range, depth, and bearing estimation errors, which, according to theory, depend mainly on the source azimuth. In particular, range and depth estimation errors are larger for source locations close to broadside to the array and smaller towards endfire, and they increase with range. Conversely, bearing estimation errors are larger close to endfire and smaller towards broadside. Localizations in this paper were performed to ranges of about 3.5 km. The limiting factors for localization to longer ranges were the loss of ability to resolve direct and surface-reflected arrivals as well as the self-noise of the hydrophones. Full article
(This article belongs to the Special Issue Advances in Undersea Remote Sensing)
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Open AccessArticle
Compressive Sound Speed Profile Inversion Using Beamforming Results
Remote Sens. 2018, 10(5), 704; https://doi.org/10.3390/rs10050704
Received: 9 April 2018 / Revised: 24 April 2018 / Accepted: 2 May 2018 / Published: 4 May 2018
Cited by 3 | PDF Full-text (8178 KB) | HTML Full-text | XML Full-text
Abstract
Sound speed profile (SSP) significantly affects acoustic propagation in the ocean. In this work, the SSP is inverted using compressive sensing (CS) combined with beamforming to indicate the direction of arrivals (DOAs). The travel times and the positions of the arrivals can be [...] Read more.
Sound speed profile (SSP) significantly affects acoustic propagation in the ocean. In this work, the SSP is inverted using compressive sensing (CS) combined with beamforming to indicate the direction of arrivals (DOAs). The travel times and the positions of the arrivals can be approximately linearized using their Taylor expansion with the shape function coefficients that parameterize the SSP. The linear relation between the travel times/positions and the shape function coefficients enables CS to reconstruct the SSP. The conventional objective function in CS is modified to simultaneously exploit the information from the travel times and positions. The SSP is estimated using CS with beamforming of ray arrivals in the SWellEx-96 experimental environment, and the performance is evaluated using the correlation coefficient and mean squared error (MSE) between the true and recovered SSPs, respectively. Five hundred synthetic SSPs were generated by randomly choosing the SSP dictionary components, and more than 80 percent of all the cases have correlation coefficients over 0.7 and MSE along depth is insignificant except near the sea surface, which shows the validity of the proposed method. Full article
(This article belongs to the Special Issue Advances in Undersea Remote Sensing)
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Open AccessArticle
The Effect of Surface Waves on Airborne Lidar Bathymetry (ALB) Measurement Uncertainties
Remote Sens. 2018, 10(3), 453; https://doi.org/10.3390/rs10030453
Received: 8 February 2018 / Revised: 2 March 2018 / Accepted: 7 March 2018 / Published: 13 March 2018
Cited by 3 | PDF Full-text (20529 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Airborne Lidar Bathymetry (ALB) provides a rapid means of data collection that provides seamless digital elevation maps across land and water. However, environmental factors such as water surface induce significant uncertainty in the ALB measurements. In this study, the effect of water surface [...] Read more.
Airborne Lidar Bathymetry (ALB) provides a rapid means of data collection that provides seamless digital elevation maps across land and water. However, environmental factors such as water surface induce significant uncertainty in the ALB measurements. In this study, the effect of water surface on the ALB measurements is characterized both theoretically and empirically. Theoretical analysis includes Monte Carlo ray-tracing simulations that evaluate different environmental and hardware conditions such as wind speed, laser beam footprint diameter and off-nadir angle that are typically observed in ALB survey conditions. The empirical study includes development of an optical detector array to measure and analyze the refraction angle of the laser beam under a variety of environmental and hardware conditions. The results suggest that the refraction angle deviations ( 2 σ ) in the along-wind direction vary between 3–5° when variations in wind speed, laser beam footprint size and the laser beam incidence angle are taken into account. Full article
(This article belongs to the Special Issue Advances in Undersea Remote Sensing)
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Open AccessArticle
Seismic Remote Sensing of Super Typhoon Lupit (2009) with Seismological Array Observation in NE China
Remote Sens. 2018, 10(2), 235; https://doi.org/10.3390/rs10020235
Received: 26 December 2017 / Revised: 27 January 2018 / Accepted: 1 February 2018 / Published: 3 February 2018
Cited by 2 | PDF Full-text (8622 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The p-wave double-frequency (DF) microseisms generated by super typhoon Lupit (14–26 October 2009) over the western Pacific Ocean were detected by an on-land seismological array deployed in Northeastern China. We applied a frequency-domain beamforming method to investigate their source regions. Comparing with [...] Read more.
The p-wave double-frequency (DF) microseisms generated by super typhoon Lupit (14–26 October 2009) over the western Pacific Ocean were detected by an on-land seismological array deployed in Northeastern China. We applied a frequency-domain beamforming method to investigate their source regions. Comparing with the best-track data and satellite observations, the located source regions of the p-wave DF microseisms, which corresponded to the strongest ocean wave–wave interactions, were found to be comparable to the typhoon centers in the microseismic frequency band of ~0.18–0.21 Hz. The p-wave DF microseisms were probably excited by the nonlinear interaction of ocean waves generated by the typhoon at different times, in good agreement with the Longuet–Higgins theory for the generation of DF microseisms. The localization deviation, which was ~120 km for typhoon Lupit in this study, might depend on the speed and direction of typhoon movement, the geometry of the seismological array, and the heterogeneity of the solid Earth structure. The p-wave DF microseisms generated in coastal source regions were also observed in the beamformer outputs, but with relatively lower dominant frequency band of ~0.14–0.16 Hz. These observations show that the p-wave DF microseisms generated near typhoon centers could be used as a seismic remote sensing proxy to locate and track typhoons over the oceans from under water in a near-real-time and continuous manner. Full article
(This article belongs to the Special Issue Advances in Undersea Remote Sensing)
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Open AccessArticle
Instantaneous 3D Continental-Shelf Scale Imaging of Oceanic Fish by Multi-Spectral Resonance Sensing Reveals Group Behavior during Spawning Migration
Remote Sens. 2018, 10(1), 108; https://doi.org/10.3390/rs10010108
Received: 17 December 2017 / Revised: 17 December 2017 / Accepted: 10 January 2018 / Published: 14 January 2018
Cited by 1 | PDF Full-text (3855 KB) | HTML Full-text | XML Full-text
Abstract
The migration of extensive social groups towards specific spawning grounds in vast and diverse ocean environments is an integral part of the regular spawning process of many oceanic fish species. Oceanic fish in such migrations typically seek locations with environmental parameters that maximize [...] Read more.
The migration of extensive social groups towards specific spawning grounds in vast and diverse ocean environments is an integral part of the regular spawning process of many oceanic fish species. Oceanic fish in such migrations typically seek locations with environmental parameters that maximize the probability of successful spawning and egg/larval survival. The 3D spatio-temporal dynamics of these behavioral processes are largely unknown due to technical difficulties in sensing the ocean environment over wide areas. Here, we use ocean acoustic waveguide remote sensing (OAWRS) to instantaneously image immense herring groups over continental-shelf-scale areas at the Georges Bank spawning ground. Via multi-spectral OAWRS measurements, we capture a shift in swimbladder resonance peak correlated with the herring groups’ up-slope spawning migration, enabling 3D spatial behavioral dynamics to be instantaneously inferred over thousands of square kilometers. We show that herring groups maintain near-bottom vertical distributions with negative buoyancy throughout the migration. We find a spatial correlation greater than 0.9 between the average herring group depth and corresponding seafloor depth for migratory paths along the bathymetric gradient. This is consistent with herring groups maintaining near-seafloor paths to both search for optimal spawning conditions and reduce the risk of predator attacks during the migration to shallower waters where near-surface predators are more dangerous. This analysis shows that multi-spectral resonance sensing with OAWRS can be used as an effective tool to instantaneously image and continuously monitor the behavioral dynamics of swimbladder-bearing fish group behavior in three spatial dimensions over continental-shelf scales. Full article
(This article belongs to the Special Issue Advances in Undersea Remote Sensing)
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Open AccessArticle
Angular Resolution Enhancement Provided by Nonuniformly-Spaced Linear Hydrophone Arrays in Ocean Acoustic Waveguide Remote Sensing
Remote Sens. 2017, 9(10), 1036; https://doi.org/10.3390/rs9101036
Received: 18 August 2017 / Revised: 2 October 2017 / Accepted: 3 October 2017 / Published: 11 October 2017
Cited by 4 | PDF Full-text (4875 KB) | HTML Full-text | XML Full-text
Abstract
Uniformly-spaced apertures or subapertures of large, densely-sampled, discrete linear receiver arrays are often used in remote sensing to increase the signal-to-noise ratio (SNR) by coherent beamforming that reduces noise coming from directions outside the signal beam. To avoid spatial aliasing or the presence [...] Read more.
Uniformly-spaced apertures or subapertures of large, densely-sampled, discrete linear receiver arrays are often used in remote sensing to increase the signal-to-noise ratio (SNR) by coherent beamforming that reduces noise coming from directions outside the signal beam. To avoid spatial aliasing or the presence of grating lobes in real spatial directions, the uniformly-spaced array inter-element spacing d sets a limit on the maximum frequency f max < c / 2 d of signals suitable for beamforming with the array, where c is the medium’s wave propagation speed. Here, we show that a nonuniformly-spaced array, for instance, formed by combining multiple uniformly-spaced subapertures of a nested linear array, can significantly enhance the array angular resolution while simultaneously avoiding dominant grating lobes in real angular space, even for signals with frequencies beyond the maximum that the array is designed for. The array gain, beam width, and maximum grating lobe height are quantified for the Office of Naval Research Five Octave Research Array (ONR-FORA) for various combinations of its uniformly-spaced subapertures, leading to nonuniformly-spaced subarrays. Illustrative examples show angular resolution enhancement provided by the nonuniformly-spaced ONR-FORA subarrays over that of its uniformly-spaced individual subaperture counterparts in both active and passive ocean acoustic waveguide remote sensing, drawn from measurements in the Gulf of Maine 2006 Experiment. Full article
(This article belongs to the Special Issue Advances in Undersea Remote Sensing)
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Open AccessArticle
Active Nonlinear Acoustic Sensing of an Object with Sum or Difference Frequency Fields
Remote Sens. 2017, 9(9), 954; https://doi.org/10.3390/rs9090954
Received: 26 July 2017 / Revised: 30 August 2017 / Accepted: 6 September 2017 / Published: 14 September 2017
Cited by 2 | PDF Full-text (2980 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A number of nonlinear acoustic sensing methods exist or are being developed for diverse areas ranging from oceanic sensing of ecosystems, gas bubbles, and submerged objects to medical sensing of the human body. Our approach is to use primary frequency incident waves to [...] Read more.
A number of nonlinear acoustic sensing methods exist or are being developed for diverse areas ranging from oceanic sensing of ecosystems, gas bubbles, and submerged objects to medical sensing of the human body. Our approach is to use primary frequency incident waves to generate second order nonlinear sum or difference frequency fields that carry information about an object to be sensed. Here we show that in general nonlinear sensing of an object, many complicated and potentially unexpected mechanisms can lead to sum or difference frequency fields. Some may contain desired information about the object, others may not, even when the intention is simply to probe an object by linear scattering of sum and difference frequency incident waves generated by a parametric array. Practical examples illustrating this in ocean, medical, air and solid earth sensing are given. To demonstrate this, a general and complete second-order theory of nonlinear acoustics in the presence of an object is derived and shown to be consistent with experimental measurements. The total second-order field occurs at sum or difference frequencies of the primary fields and naturally breaks into (A) nonlinear waves generated by wave-wave interactions, and (B) second order waves from scattering of incident wave-wave fields, boundary advection, and wave-force-induced centroidal motion. Wave-wave interactions are analytically shown to always dominate the total second-order field at sufficiently large range and carry only primary frequency response information about the object. As range decreases, the dominant mechanism is shown to vary with object size, object composition, and frequencies making it possible for sum or difference frequency response information about the object to be measured from second-order fields in many practical scenarios. It is also shown by analytic proof that there is no scattering of sound by sound outside the region of compact support intersection of finite-duration plane waves at sum or difference frequencies, to second-order. Analytic expressions for second-order fields due to combinations of planar and far-field wave-wave interactions are also derived as are conditions for when wave-wave interactions will dominate the second order field. Full article
(This article belongs to the Special Issue Advances in Undersea Remote Sensing)
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