The Student Poster Competition was held at OCEANS 13 Bergen, June 11–13, 2013 in Bergen, Norway. The conference was held in the exhibition hall of the Grieghallen conference center near the historic wharf area of Bergen. The following 21 students presented their posters:
Kazuki Abukawa, University of Tokyo
Sharbari Banerjee, Indian Institute of Technology-Delhi
Daniel Bongiorno, University of Sydney
Javier Busquets, Universidad Austral de Chile
Fauston Ferreira, Consiglio Nazionale delle Ricerche
Matthew Hall, University of Victoria
Chen Li, Memorial University of Newfoundland
Peng Liu, Kobe University
Ahmed Nait-Chabane, ENSTA Bretagne
Samir Ouelha, DCNS
Serena Parton, Florida Atlantic University
Himansu Pradhan, Indian Institute of Technology-Delhi
Qunyan Ren, Universitè libre de Bruxelles
Thomas Riedl, University of Illinois
Augustin Saucan, Institut Mines-Telecom Bretagne
Bo-min Seo, Kyungpook National University
Asm Shihavuddin, University of Girona
Joaquin Aparicio Sosa, University of Alcalá
Arnau Carrera Viñas, University of Girona
Carlos Viñolo, Polytechnic University of Catalonia
Xiaoxia Yang, Chinese Academy of Sciences
The students presented their posters to a panel of judges who made the following awards that were presented Wednesday night at the conference banquet.
The abstracts for each of the presented posters are reprinted below. The full poster paper of the first place winner is included following this article.
Kazuki Abukawa, University of Tokyo, Diagnostic methods of quay wall with acoustic measurement systems
Abstract—We used two acoustic measurement systems to assess the state of a quay wall. Collapse and subsidence of qßuay walls at harbors are often reported, and the development of a diagnostic method to help prevent collapse has become a significant concern. Collapse normally occurs because of an air hole inside the quay wall. Therefore, a robust, accurate diagnostic system to detect air holes is required. Hence, we evaluated a new diagnostic system that can assess the inside and outside states of an underwater quay wall. In this study, two acoustic measurement systems are utilized: dual-frequency identification sonar (DIDSON) and a narrow-beam parametric sub-bottom profiler (SES2000). The field experiment was performed at Iwanai port in Hokkaido, Japan (42° 59' N, 140° 30' E) on a damaged quay wall. DIDSON raw data was used to generate an image mosaic and a three-dimensional image of the quay wall surface. SES2000 created an acoustic profile of the inside of the quay wall. External and internal acoustic images of the damaged quay wall were reconstructed by data collected by DIDSON and SES2000. We detected a corrosion hole and age deterioration at some survey points using two- and three-dimensional images. The state of the quay wall was quantified and compared with the results obtained from direct underwater measurements by a diver.
Sharbari Banerjee, Indian Institute of Technology-Delhi, Underwater Acoustic Noise with Generalized Gaussian Statistics: Effects on Error Performance
Abstract—Noise in an underwater acoustic (UWA) channel does not necessarily follow Gaussian statistics, especially in a shallow water environment which is dominated by impulsive noise sources. However most of the receivers are designed with the assumption that the channel noise is additive white Gaussian (AWGN). Such receivers may not be the optimum ones to deal with the non-Gaussian UWA noise. Several non-Gaussian statistics have been proposed in previous literature to model UWA noise among which the Generalized Gaussian (GG) model has been very popular due to its flexible parametric form. However, to the best of our knowledge, no analytical error analysis with the assumption of channel noise being generalized Gaussian has yet been reported. In this paper, we derive the analytical expression for probability of error considering the presence of GG noise in the UWA channel. We also try to study the performance of an AWGN receiver in the presence of non-Gaussian noise. We consider three different communication systems using BPSK, QPSK and M-ary PAM constellations, and observe, for all three of them, that if noise kurtosis is greater than the Gaussian kurtosis, the system performance degrades. Thus here is an initial phase of designing UWA system with GG noise assumptions instead of the traditional Gaussian receiver. It is still a matter of argument, due to all possible redesign complexities, whether it is worth taking all the redesign complexities or the performance degradation can be tolerated as per the requirements of system application.
Daniel Bongiorno, University of Sydney, Dynamic Spectral-Based Underwater Colour Correction
Abstract—Optical sensing in an underwater environment can be challenging due to the complex attenuation and scattering properties of the water. These cause colour changes which can be variant on factors such as the constituents within the water, sunlight/weather changes and distance to the object of interest. It is desirable to correct for the water’s influence so as to recover a true reflectance/colour of the imaged scene. This is necessary in the application of benthic mapping where producing inter- and intra-site colour consistent images is important for classification and characterisation of these habitats. We present a new method which involves sensing the incoming irradiance to the scene from two locations above and below the water and colour correcting the image. The light is sensed in the hyperspectral domain, leading to other uses in the examination of the water column. In this paper we present colour correction in the trichromatic domain but this is equally applicable in the hyperspectral domain.
Javier Busquets, Universidad Austral de Chile, AUV and ASV in twinned navigation for long term multipurpose survey applications
Abstract—The coordination between a fleet of ocean automatic vehicles is an interesting area of research. The communication between an Autonomous Underwater Vehicle (AUV) and in-shore stations is a difficult question. Satellite communications are expensive; they provide only a limited bandwidth and the link is not always guaranteed when it is needed. High-speed communications are difficult from underwater vehicles since their antennas are affected by the sea surface conditions when they are on the surface, especially when rough sea conditions are present. Using a Surface Autonomous Vehicle (SAV) in the proximity of the AUV as a coordination station between a Command Center (CC) in shore and the AUV fleet will be an advantage for reaching a good guaranteed link between shore and the individual vehicles. The constraint of avoiding costly satellite communications on AUVs leads to the consideration of using commercial inexpensive communication systems based on UMTS and WIFI protocols, together with inexpensive acoustic underwater devices for range and bearing control and basic communications. In order to be useful for the mission the previously mentioned surface vehicle faces the challenge of operating in a wide range of weather conditions. In this paper a solution is proposed by considering a dual system composed by a SAV and a fleet of AUVs in tandem navigation strategy. In order to avoid vehicle damage, malfunction or loss of communication between shore and AUVs, robust and fault tolerant dual system propulsion and a multiple communication platform ASV is proposed.
Fauston Ferreira, Consiglio Nazionale delle Ricerche (CNR-IEIIT), Binary visual features for ROV motion estimation
Abstract—Binary feature descriptors are a recent and promising trend in the computer vision field. Nonetheless, they are not yet enough studied when compared to the more established floating-point features. Thus, the need of testing this kind of feature descriptors arises. In particular, in the underwater domain very few works used binary feature descriptors. Therefore, this article tries to explore this recent trend and to test the latest algorithms of this kind. The context of application is Remotely Operated Vehicle (ROV) motion estimation. Experimental data is used to validate each approach and both a qualitative and quantitative analysis is shown. The results show that BRIEF is the best approach for this kind of application.
Matthew Hall, University of Victoria, Evolving Offshore Wind: A Genetic Algorithm-Based Support Structure Optimization Framework for Floating Wind Turbines
Abstract—This paper presents a genetic algorithm-based optimization framework for floating offshore wind turbine support structures. Using a nine-variable support structure parameterization, this framework spans a greater extent of the design space than preexisting optimization approaches in the literature. With a frequency-domain dynamics model that includes linearized hydrodynamic forces, linearized mooring forces, and linearized wind turbine effects, the framework provides a good treatment of the important physical considerations while still being computationally efficient. The genetic algorithm optimization approach provides a unique ability to visualize the design space. Application of the framework to a hypothetical scenario demonstrates the framework’s effectiveness and identifies multiple local optima in the design space—some of conventional configurations and others more unusual. By optimizing to minimize both support structure cost and root-mean-square nacelle acceleration and plotting the design exploration in terms of these quantities, a Pareto front can be seen. Clear trends are visible in the designs as one moves along the front: designs with three outer cylinders are best below a cost of $6M, designs with six outer cylinders are best above a cost of $6M, and heave plate size increases with support structure cost. The complexity and unconventional configuration of the Pareto optimal designs may indicate a need for improvement in the framework’s cost model.
Chen Li, Memorial University of Newfoundland, Sea surface wind retrieval from GNSS delay-Doppler map using two-dimension least-squares fitting
Abstract—In this paper, a novel method is presented to retrieve sea surface wind speed and direction by fitting the two-dimensional simulated GNSS-R DDMs to measured data. The signal scattering model of Z-V and the sea surface roughness model of Cox and Munk are employed for the DDM simulation, and an 18-second incoherent correlation is performed on the measured signal to reduce the noise level. Meanwhile, a variable step-size iteration as well as a fitting threshold are used to reduce the computational cost and error rate of the fitting procedure, respectively. Unlike previous methods, all the DDM points with normalized power higher than the threshold are used in the least-square fitting. An optimal fitting threshold is also proposed. To validate the proposed method, the retrieving results based on a dataset from the UK-DMC satellite are compared with the in-situ measurements provided by the National Data Buoy Center, and good correlation is observed between the two.
Peng Liu, Kobe University, Velocity Error Analysis of Dual Time Interval Pulse-to-Pulse Coherent Doppler Sonar
Abstract—As a Pulse-to-Pulse coherent Doppler sonar has advantages of quick-response and high degree of accuracy and precision, it becomes widely used in the laboratory and the sea. However, the occurrence of range and velocity ambiguities brings serious limitations on the more general applications of the sonar. One method to deal with the ambiguities is to implement a dual pulse interval method that can provide acceptable ambiguity velocity while requiring uncomplicated equipment. In this paper, three measurement error analyses are carried out. One is a theoretical analysis as one bound of measurement error. The second is a numerical analysis by simulations, and the last is experimental analysis in the laboratory. The results of the error analyses verified that the dual time interval pulse-to-pulse coherent Doppler sonar could enlarge the ambiguity velocity with high accuracy and precision.
Ahmed Nait-Chabane, ENSTA Bretagne, Sidescan Sonar Imagery Segmentation with a Combination of Texture and Spectral Analysis
Abstract—This paper deals with the seabed classification from textured sonar images and specially the potential of the combination of features extracted from co-occurrences matrices and directional filter bank (DFB). The texture analysis based on the co-occurrences matrices is strongly dependent on the choice of parameter values (e.g. the distance and the angular direction for the estimation of the number of transitions). In most cases the choice is not trivial. To get representative features from textures with different spatial frequencies, a comprehensive set of co-occurrence matrices with corresponding displacements and orientation has to be computed. In this work, we investigate a non-classical approach based on the DFB. The approach uses a decomposition of the Fourier spectrum into three spectral bands: low, medium and high frequencies. A subsequent analysis of the pattern isotropy is conducted by dividing the medium spectral band into small, overlapped, angular sectors. The features extracted from this process are assessed so as to determine their potential on the classification performances. First, a comparison with classification performances result given by texture features derived from grey level co-occurrences matrices (GLCM) is made. Finally the global performance of the segmentation is assessed using the spectral features, the features extracted from GLCM and the grazing angle. The Klein 5000 experimental data used in this study have been acquired by DGA/GESMA during BP 02 experiment conducted by NURC.
Samir Ouelha, DCNS, A new time-frequency representation for underwater acoustic signals: the denoised hearingogram
Abstract—With the aim to develop a new process useful for underwater acoustic signal identification, with human perception considerations, we have presented in a previous paper the hearingogram. Despite the presence of noisy terms, experimentations on real data have revealed the validity of such an approach. In order to reduce the noise level, we propose, in this paper, to modify this time-frequency transform using a wavelet based denoising method. Experimentation on real underwater signals are presented and discussed.
Serena Parton, Florida Atlantic University, Acquisition and Registration of Bathymetric Acoustic Data and MOFSLI (Multiple Overlapping Field of View Serial Laser Imager)
Abstract—Obtaining three-dimensional sub-centimeter resolution views of the seafloor is advantageous in many areas. Sonar has the ability to provide three-dimensional bathymetry while laser line scan (LLS) systems are able to provide sub-centimeter resolutions. The ability to acquire and register these datasets simultaneously can provide these detailed seafloor views. A LLS prototype was developed at Harbor Branch Oceanographic Institute (HBOI) for use in conjunction with a sonar system. This prototype is coined Multiple Overlapping Field of View Serial Laser Imager (MOFSLI). The eventual goal is to create a combined laseracoustic survey sensor for an autonomous underwater vehicle (AUV). This paper gives an overview of the MOFSLI prototype system components as well as the experimental procedures and the process of registering the optical and acoustic datasets. Sea trials with the combined system were performed and data was successfully collected and registered.
Himansu Pradhan, Indian Institute of Technology-Delhi, Simulation of internal waves in the western Bay of Bengal using MITGCM: A case study
Abstract—MITgcm model is adopted probably first time for the western shelf region of the Bay of Bengal to model internal waves. Monthly climatological wind and density fields are considered in the model with real-time tides to generate internal waves in the region. The model simulations are compared with the actual observations available during 19–21 February 2012. Time series temperature data is collected at two locations off Gopalpur and is used to study internal wave characteristics. Thermal oscillations and energy spectra are studied and compared at the observed locations. It is found that internal waves of semi-diurnal nature are predominant over this region.
Qunyan Ren, Universitè libre de Bruxelles, Hybrid method to extract striation features from ship noise spectrogram
Abstract—The features of interference striations excited by a passing ship are strongly determined by the acoustic waveguide properties. These striation position and orientation have been used for environmental inverse problems. The ship noise spectrogram can be very noisy due to measurement conditions, i.e., high ambient noise level or transmission loss noise. It is necessary to enhance the underlying interference structure before extracting the striation features of interest. A hybrid image processing method is introduced in this paper for interference structure enhancement. It first uses a Gabor filter bank to provide the local image intensity maximum value in different directions, and then locally equalizes the resulting image. Different ship noise data sets from different experiments are processed by the proposed method. Preliminary results demonstrate that the hybrid method can effectively identify striations in both low and high frequency regions, especially for the data set collected under particularly difficult measurement conditions due to strong current, surface wave, high ambient noise level, complex time-varying source spectrum, etc. Consequently, better estimates of the position and orientation of local striations can be obtained, which will likely improve the accuracy of striation-based inversion techniques.
Thomas Riedl, University of Illinois, MUST-READ: MUltichannel Sample-by-sample Turbo Resampling Equalization And Decoding
Abstract—When an underwater acoustic modem is installed on a mobile platform such as an underwater vehicle, a buoy, or a surface vessel, Doppler effects distort the acoustic signal significantly. The acoustic path between a surface vessel and an underwater vehicle, for example, can experience Mach numbers of one percent and more which can be catastrophic if not compensated dynamically. In this paper, we derive a sample-by-sample, recursive resampling technique, in which time-varying Doppler is explicitly modeled, tracked and compensated. Integrated into an iterative turbo equalization based receiver, this novel Doppler compensation technique achieves unprecedented communication performance in field tests and simulations. Our field data stems from the MACE10 experiment conducted in the shallow waters 100 km south of Martha’s Vineyard, MA. Under challenging conditions (harsh multi-path, ranges up to 7.2 km, SNRs down to 2 dB and relative speeds up to 3 knots) our receiver achieved a raw data rate of over 39 kbits/s and a perfectly reliable net data rate of over 23 kbits/s (taking into account the overhead from equalizer training and channel coding) in less than 10 kHz of bandwidth. To illustrate the robustness of this approach to high rates of Doppler, a variety of simulations are also provided. We demonstrate that the performance of our algorithm does not depend on the absolute level of Doppler, but only on the rate of its variation.
Augustin Saucan, Institut Mines-Telecom Bretagne, Interacting Multiple Model Particle Filters for Side Scan Bathymetry
Abstract—In this paper we propose a multiple sea floor model based approach to improve bathymetry estimation with tracking algorithms. Traditionally interferometry is used to estimate the phase difference of signals received by two sensors, implicitly the direction of arrival (DOA) of the wave impinging both sensors. In our approach, we employ a state space model to describe data collected by a multi-sensor side scan sonar, and the evolution of the underlying DOA angle. The challenge with space state models is choosing the right model, and detecting the switch between models. We propose the use of several models that describe different sea-floor patterns and merge them within the framework of the interacting multiple model (IMM). Since the sonar array processing problem is non-linear and non-Gaussian, we propose an IMM particle filter algorithm to provide robust tracking while not sacrificing performance. Also an interesting new application is the swath segmentation, which appears as a side result implied by calculating the different model probabilities.
Bo-min Seo, Kyungpook National University, Design for Underwater Code Division Multiple Access Transceiver
Abstract— Code division multiple access (CDMA) is one of the promising medium access control (MAC) schemes for underwater acoustic sensor networks because of its robustness against frequency-selective fading and high frequency-reuse efficiency. In this study, we design the forward and reverse links of a CDMA transceiver so that it can be operated in underwater acoustic channel environments, and we evaluate its performance by computer simulations. A pseudorandom noise code acquisition process is added for phase-error correction before decoding the user data by means of a Walsh code in the receiver.
Asm Shihavuddin, University of Girona, Automated classification and thematic mapping of bacterial mats in the North Sea
Abstract—With the current availability of high quality optical sensors and the advancements of Autonomous Underwater Vehicles (AUVs), it is becoming increasingly accessible to acquire extremely large sets of benthic habitat images. Manual characterization and classification of such large number of images for relevant geological or benthic features can become very difficult and time consuming. This paper presents a novel method for automated segmentation, classification and thematic mapping of bacterial mat from shell chaff and sand, on mosaics created from an image survey on the North Sea. The proposed method uses completed Gabor filter response, grey level co-occurrence matrix (GLCM) and local binary pattern (CLBP) as feature descriptors. After chi-square and Hellinger kernel mapping of feature vector, Probability Density Weighted Mean Distance (PDWMD) is used for classification. Initial segmentation is done using TurboPixels. Our proposed method achieves the highest overall classification accuracy and have moderate execution times compared with the set of methods that are representative of the state-of-the-art in automated classification of seabed images. Our work illustrates that applying automated classification techniques to mosaic composites produces a rapid (in terms of expert annotation time) technique of characterizing benthic areas that can be used to track changes over time.
Joaquin Aparicio Sosa, University of Acalá, Influence of different phenomena on the errors in distance measurement using underwater acoustics coded signals
Abstract—The underwater channel is a highly variable medium due to the influence of several effects on the acoustic signal, and the physical variability of the environment. This behavior makes the underwater channel a very difficult one to model, and also a complex environment to work with. In acoustic-based positioning or sonar systems, where it is important to know accurately the time-of-flights of the signals, pseudorandom codes provide immunity to some of these effects. In this work, a statistical study of the influence in range detection of common effects in underwater acoustics, such as noise and wind speed, is presented. Through this study, the performance of a relative positioning system is also studied for different scenarios.
Arnau Carrera Viñas, University of Girona, Towards valve turning with an AUV using Learning by Demonstration
Abstract—AUVs have experimentally done the first steps to solve basic intervention tasks. First results have been promising in the task of retrieving an object from the seabed. In this paper we extend the complexity of the task with the help of a Learning by Demonstration (LbD) approach. An extension of a LbD algorithm to learn the pose and orientation of the trajectory is presented to achieve a valve turning task. A batch of demonstrations done in ROV mode is used by the LbD to learn the trajectory, taking advantage of the experience of the pilots. Moreover, the paper presents a controller able to coordinate the movement of the manipulator using the position or the orientation of the end-effector and also moving the AUV when it is required. Both systems have been tested together in a simulated environment to solve the task of interacting with a valve located on a ROV panel. The experiments have been done in an environment without perturbations and in an environment with different perturbations. The method has been able to overcome the perturbations and complete the task successfully. Furthermore, the proposed controller has simplified the use of the manipulator during the intervention task. The robot is equipped with a 4 DOFs manipulator having a griper as end effector to operate the T bar handles found in the panel. Panel and valve handle position and orientation are detected by a computer vision program based on template matching.
Carlos Viñolo, Polytechnic University of Catalonia, Sea motion electrical energy generator for low-power applications
Abstract—The main problematic about electronic systems deployed in the sea for long periods of time, is to find a feasible way to supply them with the necessary amount of power and no direct supervision. In this paper a new idea is proposed and studied to supply deep-sea low-consumption devices using low-cost disk piezoelectric elements. These piezoelectric components, together with a horizontal balance-like physical pendulum, create an electrical power generator that harvests the mechanical energy brought by the sea movements, preferably from the heave and pitch motion that sea waves induce in a moored-floating body as might be a buoy. The main purpose of this system is to unrelate the rate of impacts to the piezoelectric material from its natural oscillation frequency, making it viable to harvest energy from a slow motion environment such as the sea. Equations relating the energy extraction are presented and different experimentations are worked out to characterize the piezo elements. Finally a prototype with a proposed electronic harvesting system is built and tested in a real medium, showing the results before concluding the article.
Xiaoxia Yang, Chinese Academy of Sciences, Soft Decision Feedback Equalizer for Channels with Low SNR in Underwater Acoustic Communications
Abstract—Decision feedback equalizer (DFE) uses the past decisions in the feedback filter to mitigate the intersymbol interference (ISI). For the underwater acoustic channel, the impulse response often covers tens to hundreds of symbols, requiring at least tens of taps in the feedback filter. The error propagation easily occurs when the signal to noise ratio (SNR) decreases. In order to improve the DFE performance, a soft decision device is used in the feedback loop. Differently with the hard DFE, the soft DFE takes into account the reliability of the decisions, and the likelihood of these decisions is feedback to mitigate the ISI. The soft DFE is demonstrated to be useful from two aspects in the real sea test: 1). It can overcome the SNR loss brought by the timing synchronization error; 2). In the decision-directed mode, the hard DFE easily diverges facing the occasional powerful noises, while the soft DFE is robust to more likely to converge again without the help of any training sequence.