Comments: download file (cintal_rep).
Ref.: SiPLAB Report 02/17, SiPLAB, University of Algarve, February 2017.
In seismic geo-acoustic exploration, the use of ships towed long cables equipped with hydrophones, known as streamers, is of major concern due to the complexity of its operation. The European project WIMUST aims to improve the efficacy of actual geo-acoustic surveys through the use of autonomous underwater vehicles (AUV) towing short streamers. A Dual Accelerometer Vector Sensor (DAVS) was developed in order to complement the streamer’s data, allowing for the reduction of their size and facilitating the operation of the WiMUST distributed sensor configuration. Each DAVS consists of two tri-axial accelerometers and one hydrophone aligned along the vertical axis. This configuration has the ability to cancel or significantly attenuate the direct and the surface reflection paths, which are undesirable in seismic imaging. The objective of this report is to describe a DAVS’s calibration test and to present experimental results on the estimation of azimuthal directions when the DAVS is in motion. The calibration test took place on September 26, in the Oceanarium shallow pond, Lisbon. Signals in the 1-2 kHz band were emitted by the Lubell source deployed at 1.5 m depth and acquired by the DAVS mounted on the MEDUSA class AUV, from IST, which was following a pre-programed path with a 0.26 m/s nominal speed. The azimuth estimates are coherent with the MEDUSA trajectories even in curved paths where the thruster noise increases.