Simrad ES70 Operator's Manual page 121

When you use bottom expansion, the water surface is not the reference any longer, but
the bottom is. It is always 0. That means that the bottom in this echogram will always be
flat, even though it may vary in the upper echogram. To choose a vertical depth range for
the bottom expansion, set
the echogram. Then, set
height above the bottom. In this echogram positive depth is below the bottom, while
negative depth is above.
Typical settings may be:
• Range = 15 m
• Start range = –10 m
This provides you with a 15 meters high phased area starting at 10 meters above the
bottom to 5 meters below it.
Example 19 Start Range and Range in bottom related echogram
In a bottom echogram, set the
make the echogram start from 5 meters above the bottom. Set
5 meters plus 10 = 15 meters. The echogram will now show the area from
5 meters above the depth, and down to 10 meters "below" the bottom. The
bottom contour will appear as a flat line.
343539/B
to a positive value. This is the total vertical range of
Range
to a negative value. This is the echogram's start
Start Range
Start Range
Echo sounder theory
value to –5 meters. This will
Range
to the
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