Swath bathymetry with GLORIA

For many years, GLORIA has been producing sonar images of the deep ocean floor. In the mid-1980's, the SeaMARC II system came to prominence producing depth values as well as sonar images. The basic method compares the phases of the signals returning from the seafloor to two rows of transducers....

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Bibliographic Details
Published in:IEEE journal of oceanic engineering 1996-10, Vol.21 (4), p.545-553
Main Authors: Le Bas, T.P., Somers, M.L., Campbell, J.M., Beale, R.
Format: Article
Language:English
Subjects:
Earth sciences
Earth, ocean, space
Exact sciences and technology
External geophysics
Image converters
Marine
Marine geology
Marine optics and underwater sound
Oceanographic techniques
Oceans
Phase estimation
Physics of the oceans
Reverberation
Sea floor
Sonar
Strips
Time frequency analysis
Transducers
Underwater sound
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Summary:For many years, GLORIA has been producing sonar images of the deep ocean floor. In the mid-1980's, the SeaMARC II system came to prominence producing depth values as well as sonar images. The basic method compares the phases of the signals returning from the seafloor to two rows of transducers. The phase differences are converted into angles of arrival and together with the arrival times converted into range and depth values. This capability has now been added to the GLORIA system. The fact that GLORIA uses a 2s FM pulse means the backscattered reverberation can come from a strip of seafloor up to 1.5 km wide. To accommodate this, overlapping complex FFT's are used to produce a time-frequency matrix for the returning signals. In this matrix, a constant range feature appears as a diagonal. Phases are then calculated using a least-mean-squares estimate along diagonals. The main source of error and bias is due to surface reflection, and this is taken into account. The GLORIA swath bathymetry system was tested on two cruises and it was possible to produce depth contours with a good level of confidence. The total swath width was over eight water depths and would have been greater with a more favorable velocity profile. Comparison with other bathymetry data (such as multibeam systems) showed excellent correlation, having a standard deviation of only 4% of total water depth.
ISSN:0364-9059
1558-1691
DOI:10.1109/48.544064