Next: Introduction
75 kHz RDI Ocean Surveyor Evaluation:
Comparison with 150KHz Narrow Band,
R/V Endeavor, Feb. 17-23, 2001.
Draft document.
Jules Hummon - Eric Firing
Abstract:
During a recent transit from Florida to Rhode Island,
simultaneous single-ping data were recorded from two
acoustic Doppler current profilers on the R/V Endeavor: an
old
150-kHz narrow bandwidth (NB) model, and a new 75-kHz model
(Ocean Surveyor: OS) with a flat phased-array transducer,
operating alternately in narrow bandwidth (OSN) and broad
bandwidth (OSB) modes. In calm weather the NB, OSN, and OSB
data showed nearly perfect agreement, but the range of the
OSN (up to 800 m) was about twice that of the NB, and the OSB range was
about 85% of the OSN range. As weather worsened, the
returns from all three degraded, with reduced depth range
and with occasional pings returning no valid velocity
estimates. Reduction in data return was most severe in the OSB, least
severe in the NB. Performance degradation was associated
with a velocity bias towards zero in both the OSB and OSN
relative to the NB;
we believe this problem can be solved with improved
single-ping editing and averaging algorithms. Much larger
velocity bias occurred in OS bottom tracking data. Beam
sidelobes were 12-15 db higher in the OS than in the NB.
Although this did not cause obvious velocity profile errors
in the present dataset, we believe it will do so in regions
such as the eastern equatorial Pacific.
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Next: Introduction
Jules Hummon
2001-10-24