Browsing by Author "Mantouka, A."
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- On the performance of geo-acoustic estimation for a distributed sensor arrayPublication . Jesus, Sergio; Mantouka, A.; Felisberto, Paulo; Soares, CristianoThe vision underlying the Widely scalable Mobile Underwater Sonar Technology (WiMUST) project is that of developing advanced cooperative and networked control / navigation systems to enable a large number (tenths) of marine robots towing small acoustic arrays to act as a coordinated team for seismic sub-bottom imaging. The space-time coherent processing of bottom returns requires the ensemble of short acoustic arrays to be seen as a single spatially distributed sensor array. Since the vehicles are free to move along range, cross-range and depth the resulting distributed sensor array may take, at least conceptually, any spatial shape. With array shape freedom comes the question of which is the most suitable (or optimal) array geometry for sub-bottom imaging and inversion. The answer to this question hinges, among others, on the definition of performance of a seismic sub-bottom profiling system. Determining the optimal sensor array geometry is clearly a ill-posed problem, since the optimal geometry is itself bottom dependent, and there is no such environment as "one size fits all". This work addresses several criteria for sub-bottom profiling system performance including gain, resolution and probability of detection. Two physical models will be tested: one based on acoustic wave reflection used in traditional seismic imaging, and another normally used in matched-field bottom properties estimation, that includes propagation and refraction. Simulations to support the theoretical developments and algorithms were obtained on a scenario inspired in a real environment off the coast of Peljesac (Croatia).
- The application of a dual accelerometer vector sensor for the discrimination of seismic reflectionsPublication . Mantouka, A.; Felisberto, Paulo; Jesus, Sergio; J. Santos, P.; Sebastiao, Luís; Pascoal, A.This paper describes the application of a Dual Accelerometer Vector Sensor (DAVS) for the discrimination between the bottom reflections, the source direct arrival and the source ghost or multipath in an unconventional seismic acquisition scenario. The realisation of the DAVS device and the seismic acquisition scenario described in this paper, were carried out in the scope of the WiMUST project, an EU project, supported under the Horizon 2020 Framework Programme. The WiMUST project aims to improve the efficiency of the methodologies used to perform geophysical acoustic surveys at sea, using Autonomous Underwater Vehicles (AUVs) equipped with optimum sensors. In a classical reflection seismic survey scenario, the DAVS can contribute to this aim by steering its acoustic beam to the desired direction, therefore reducing the amount of post processing related to deghosting and multipath removal. Moreover, in an unconventional scenario, this steering capability offers the possibility of distinguishing between direct arrivals and multipath. In this paper, using data acquired during a WiMUST experiment, the device's directional estimation capabilities are demonstrated using a conventional beamformer for the determination of the Direction of Arrival (DOA) of seismic waves. The beamformer inputs are pressure and particle velocities in three directions. For the results presented here the pressure was derived from the devices' two accelerometers.