First results from a combination side-scan sonar and seafloor mapping system (SeaMARC II)
SeaMARC II (Sea Mapping and Remote Characterization) is both a conventional side-scan sonar and a bathymetric mapping system. It is a 12kHz, long-range, shallow-towed, high-speed system that produces an ocean floor image up to 10km wide. (By contrast SeaMARC I is a 30kHz deep towed, slow-speed side-scan only system.) Bathymetry is determined by measuring 4000 times each second the magnitude and arrival angle of narrow band acoustic energy returned from each side of ship's track. Off-line processing of this series of vectors produces a seafloor bathymetric map along the track with a width 3.4 times the water depth. A 10 knot tow capability allows more than 4000 square kilometers to be surveyed each day. In practice, the average returns from a relatively flat part of the survey area are used to generate a function relating acoustic arrival angle to measured electrical angle. This procedure corrects for local sound speed structure. With this function, the measurements from returns with adequately large magnitudes are converted to acoustic arrival angle. These angles are corrected for tow body attitude and, with the arrival times (range), are converted to horizontal (X) and vertical (Z) distances from the tow body to the reflector. Side-scan images are a combination of the small scale reflecting properties of the bottom (micro-reflectivity) and the specular reflections from bathymetric slopes (macro-reflectivity). SeaMarc II has the unique ability to acquire synoptic data that will allow the two effects to be separated. This unique combination also allows more accurate and rapid understanding of bottom character than with either output by itself.
- Research Organization:
- Hawaii Inst. of Geophysics
- OSTI ID:
- 6979008
- Report Number(s):
- CONF-830514-
- Journal Information:
- Proc., Annu. Offshore Technol. Conf.; (United States), Vol. 1; Conference: Offshore technology conference, Houston, TX, USA, 2 May 1983
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
42 ENGINEERING
SEA BED
BATHYMETRY
MAPPING
ACOUSTIC MEASUREMENTS
IMAGE CONVERTERS
IMAGE PROCESSING
IMAGE SCANNERS
KHZ RANGE 01-100
MARINE SURVEYS
SONAR
SOUND WAVES
FREQUENCY RANGE
IMAGE TUBES
KHZ RANGE
MEASURING INSTRUMENTS
PROCESSING
RANGE FINDERS
SURVEYS
580500* - Oceanography- (1980-1989)
423000 - Engineering- Marine Engineering- (1980-)