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This paper presents a polarization-based enhancing system consisting of a rotating polarizing filter and an image fusion algorithm. A prototype was developed and tested in different light conditions, from early morning to late afternoon, and recordings of underwater scenes were taken in a sea stretch of the Mediterranean sea. Several images within the polarization range of 0° to 180° were used in...
The frequency diverse multiple-input multiple-output (FD-MIMO) sonar can use a group of small-bandwidth FD pulses to synthesize a large bandwidth signal, which brings a higher range resolution than traditional methods. However the range sidelobe level (SLL) is high due to the cross-correlation function (CCF) interferences and the spectrum leakage between auto-correlation functions (ACFs) of transmitting...
Image segmentation techniques are widely used for identifying marine oil spill regions in SAR images, with one representative technique being level set evolution. The accuracy of level set evolution highly relies on a proper initial level set function which roughly captures the marine oil spill layouts in a SAR image. However, marine oil spill regions are always complicatedly shaped, and it is time-consuming...
Underwater acoustic communications performance are severely limited by the high number of reflections especially in shallow water environment so producing large delay spread on the signal during the propagation. Multiple-input-multiple-output (MIMO) solutions combined with spatial multiplexing (SM) techniques have been investigated in order to increase the communication rate despite the bandwidth-limited...
Dumped chemical weapons that are corroding and exposed to the marine environment can cause contamination and health risks for marine fauna and humans. This paper describes some of the work that is done in the EU-DAIMON (Decision Aid for Marine Munitions) project including the development of a decision support method and previous field results that indicate that bottom trawling re-suspend sediments...
Underwater object detection and tracking is of great interest for offshore defense. Recently, a new method adopting direct-current resistivity techniques was introduced to complement conventional detection method. The new detection method needs high-speed localization of underwater target object for real-time tracking. In this paper, we propose real-time localization method using grid-based template...
Measurement of the seawater temperature at different depths to get a vertical temperature profile on the water column is presented in this paper: The acquisition system based on optical fiber Bragg gratings (FBGs) and the subsequent data processed is also presented. The temperature measurements are taken in distributed points along the fiber where the Bragg gratings are located. The paper reports...
The paper provides an overview of the development of a new Introduction to Engineering and Technology course for freshmen students. The course provides an opportunity to introduce engineering students early on to the field of ocean engineering and opportunities in the Navy STEM field. The course relies heavily on a hands-on laboratory component that builds on technical content introduced in the lecture...
For earth quakes happening in the ocean, the signals will be best picked up by ocean bottom seismometers (OBS) to have their fidelty. The seismic signal picked up by OBS's is often contaminated by the ocean surface waves. In order to separate the noises due to the ocean surface wave, a differential pressure gauge (DPG) is installed on OBS to detect the pressure change purely due to the water body...
The maximum number of targets that can be uniquely identified by the traditional MIMO sonar is limited by the number of virtual sensors. To alleviate this problem, we extend the idea of nested array to the case of MIMO sonar. To utilize the enhanced degrees of freedom (DOF) provided by the nested MIMO sonar, an efficient direction of arrival (DOA) estimation method is proposed based on compressed...
A design for MIMO sonar system based on subarrary and waveform diversity is proposed in this paper. Similar to co-located MIMO radar, the sonar transmitter and receiver are both closely spaced antennas. Different from the original co-located MIMO sonar, our scheme partitions the transmitting array into several subarrays. Multiple independent waveforms would be transmitted by each subarray, and the...
The challenge in the Autonomous Underwater Vehicle (AUV) navigation technology is how to ensure precise localization accurately. Extended Kalman filter (EKF) is the most widely used navigation method. Despite its long successful application, EKF has a number of problems in application, for instance, the system motion model usually not appropriate to be described as a linear system. This paper proposed...
Mobile Underwater Acoustic Networks (MUANs) is currently a enabling technology for a wide range of applications. However, the self-localization of mobile nodes is difficult. In this paper, we propose a range-angle based self-localization scheme for MUANs. Each mobile node only communications with the anchor node which sends localization message and mobility model to the network. Ordinary nodes can...
Time reversal is an effective method for channel equalization in underwater acoustic communication. Its temporal and spatial focusing efficiently can compensate intersymbol interference (ISI) caused by a rich multipath environment inherent in underwater acoustic channel. Additionally, time reversal is a promising solution also for multiple-input/multiple-output (MIMO) communication by realizing space...
The purpose of this paper is to provide guidance for AUV manoeuvering of two vehicles missions. In this paper, the numerical simulation of interaction between two vehicles with different size is conducted using CFD code. Mesh independence is tested and then validated with experimental results in previous paper. In an aim to predict the factors that influence the hydrodynamic performance, the simulation...
A Power-over-fiber extension for an existing fixed seabed observatory is presented in this contribution. The system is characterized by its versatility in respect to the sensors with which it can operate. Turbidimetry tests and results are presented.
Disentangling the source-specific signature of petroleum biomarkers against the often stronger regional fingerprint has posed a fundamental challenge to oil-spill forensics in a petroleum-rich locale (e.g. Deepwater Horizon, Gulf of Mexico, April 2010). Two-dimensional gas chromatography (GC×GC) captures the joint peak distribution of hundreds of hydrocarbon biomarkers in crude petroleum through high-resolution...
This study concerns the implementation of an underwater positioning system in shallow water environment. Shallow water localization of the beacon is done by using the propagation of acoustic signals in water. The experiment is based on the use of a boat equipped with two hydrophones and an emitting beacon. The signal received on each sensors are processed to compute the difference in time arrival...
This article concerns the formalization of a control framework for the fish-like motion control in a fluid due to a vector field generated by point vortices so that the overall power consumption required to travel between the departure and the arrival points is minimized. The control action is synthesized by specifying the time, location and circulation of at least one vortex and the extent to which...
Underwater communication channel put various kind of challenges like extended delay spread, large Doppler shift and low coherence bandwidth. As a result of which communication at higher data rate becomes difficult, moreover it enhances the complexity in receiver design. Researchers working in this area have suggested many techniques to combat the problems asso-ciated with underwater channel. One of...
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