Reson SeaBat 7125 SV2, Operator'S Manual

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SYSTEM PERFORMANCE AND DATA TYPES
SeaBat 7125 SV2 Operator‟s Manual
Page 123 July 25, 2011
Version 3
7.4 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 ).
7.4.1 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 numb
er of samples used is marked „A‟ in
Figure 56 and is a small
percentage of the total number of samples. The noise is based on a mean of the square
of the samples in the second half of the “tail” of the detection window (marked „B‟ in
Figure 56
) and the square of the samples in the “head” of the water column (before the
first return
– marked „C‟ in
Figure 56 ).
Beams, whose SNR is greater than a predetermined threshold, will be flagged as
passing the brightness test.
For instructions on how to display the test results, see Quality in
section 5.7.4 Primary
Display Settings .
Bottom detection point
Adaptive gate
Comparison
window
A
B
C
Figure 56: Brightness Test
7.4.2 Colinearity Test
In general terms, this test will pass if a bottom detection point sample number for a given
beam falls on or near a line drawn through its neighboring beams' bottom detection
points. This is achieved using a moving polynomial fit of the points on either side of each
point. If a given point is within the window of the line fit, it is marked colinear.