ISSN:
1573-0581
Keywords:
Acoustics
;
backscattering
;
sonar image
;
multibeam echo sounder
;
sedimentology
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
,
Physics
Notes:
Abstract Since early 1991, the EM12 dual multibeam echo sounder mounted on R/V L'Atalante has been mainly used for regional mapping and more particularly for EEZ exploration. The acoustic imagery data, which is collected at the same time as the multibeam soundings, and positioned with the same accuracy, illustrates the variability of the acoustic interface. The working principles of the multibeam echo souder are at rirst presented. The backscattering phenomena are then considered, where the echo structure is interpreted in terms of insonified area, propagation loss and backscattering strength; the latter, especially important for the seafloor acoustical characterization, is described as contributions from the interface roughness and the volume inhomogeneities. Problems associated with the seafloor type interpretation from the backscattered level data are briefly evoked. Then, the various operations associated with ‘mosaic’ computations are presented, describing the transition from the original time signals to the final image usable by geologists. Three examples, selected from a large set of data collected by IFREMER for SOPAC (SOPACMAPS Project) and the Territory of New Caledonia (ZoNéCo Project), both in late 1993, show that there are well differentiated acoustic reflectivity levels. After a description of their regional geological environment, the three examples are presented with the main results. These reflectivities, not yet calibrated in terms of field truth, are tentatively related to the previous existing data on the nature of the bottom and to the basic rules of marine sedimentology.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00286090
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