Reson SeaBat 7125 ROV, Руководство оператора

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SYSTEM PERFORMANCE AND DATA TYPES
SeaBat 7125 ROV Operator‟s Manual
Page 106 May 30, 2011
Version 3
In order to achieve this uniform sounding spacing, it is necessary to decrease the beam
center-to-center spacing which requires a significant increase in the number of beams
formed. As an example, in the SeaBat 7125 ROV 400kHz system 256 or 512 beams are
formed in equiangular or equidistant mode over the same 128° (or 140°) swath. For
instructions on how to change the mode, see
section 3.3 Starting the 7k Control Center
and Sonar .
The beamformer is able to generate a receive beam centered on any angle within the
available swath and in equidistant mode a set of coefficients is selected that form a set
of receive beams that are centered on the midpoints of the footprints.
Figure 45 shows the difference in distribution between equiangular and equidistant
modes.
Figure 45: Across-Track Sounding Location on a Flat Bottom
7.3 Quality
The quality of each bathymetric bottom detection point is evaluated by the 7k Center
(see Bathy Point Color
in section 5.7.4 Primary Display Settings ).
7.3.1 Brightness Test
The brightness test measures the signal-to-noise ratio (SNR) of the signal strength
(magnitude) near the bottom detection point (as determined by the bottom detection
algorithm) versus the background noise in the rest of the beam.
The signal strength is the mean of the square of the sample intensity around the bottom
detection point. The number of samples used is marked „A‟ in
Figure 46 and is a small
percentage of the total number of samples. The noise is based on a mean of the square
of th
e samples in the second half of the “tail” of the detection window (marked „B‟ in
Figure 46
) and the square of the samples in the “head” of the water column (before the
first return
– marked „C‟ in
Figure 46 ).