Section 4 Operation
83
Adjust the Bottom Judgement Level
•If soft sludge has collected at the sea bottom, or it is the rock and the
contour variation is extreme, the Digital Depth Reading might not
coincide with the bottom echoes on the screen. In this case, adjust the
Bottom Judgment Level in the following procedure.
•In the normal operation, push the
and at the same
time to display the Bottom Judgment Level menu in the center of the
screen. Press the up or down to select the High or Low
frequency, and press it to the left or right to specify the offset value of
the Bottom Judgment Level. The offset values range between -20 and
+20, and it is set to zero for both High and Low frequencies on the
shipping from the factor. Use the following table as a guide and adjust
the offset value by looking at each screen of the High and Low
frequencies in the Standards Single Frequency mode so that the depth
reading is displayed stably.
Seabed Conditions Offset value
Rock Increase: 0 to +20
Soft sludge Decrease: -20 to 0
Note:
•If you decrease the offset value too much, the echoes of school fish
may be recognized as the sea bottom. In this case, the Depth Reading
will fluctuate. On the contrary, if you increase it too much, the sea
bottom may not recognized and no Depth Reading will not be
displayed. Be sure to adjust the offset value while looking at each
screen of both High and Low frequencies in the Standard Single
Frequency mode and check the bottom echoes and the Depth
Reading. Refer to "Seabed Conditions " p.90 for the information
about how to judge the quality of the sea bottom.
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