About Dynamic Range And Display Presentation - Simrad ES70 - REFERENCE MANUAL REV A Reference Manual

Simrad ES70
When you are looking for schools these will fill the entire beam, just as the bottom
normally does. A lot of gain is then not necessary. The
will provide an acceptable echo strength. When you use the
you will see that the bottom echo is very strong. The presentation will use stronger
colours with increasing depth.
About dynamic range and display
presentation
The ES70 echo sounder has a dynamic range of 140 dB. This means that the sounder can
receive both very strong and very weak echoes. Actually, the ES70 will detect echoes
from plankton to whales, bottom on all depths, and present the information free from
distortion. As a comparison, our old echo sounders ES380 and ET100 had a dynamic
range of approximately 65 dB.
Naturally, we can not present all these echoes on the display simultaneously, as this
would create a mess of colours.
When 12 colours are used, we create a 36 dB section and give each colour a 3 dB
strength. Every colour (3 dB) the represent a doubling of the echo strength. With the
12 colours (A) this will be a 36 dB colour range from grey to brown. Grey is used for
the weakest echoes, while the strongest echoes are brown. All echoes stronger than
brown will still be brown, while echoes weaker than grey will not be shown. The old
paper sounders had a dynamic range of 12 dB in their printouts using the "colours"
from light grey to black. The dynamic range in the ES70 colour presentation is thus a
lot larger; 24 dB or 250 times.
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The illustration shows how the gain close
to the bottom (B) is larger than just below
the transducer (A). The echoes from the fish
close to the bottom will then be shown with
the same strength as echoes from pelagic
The left vessel uses the
setting. This will cause single fishes to be
R)
shown smaller and smaller with increasing
depth, even though they may be of identical
size. The right vessel uses the
setting, and that will make identical
log R)
sized fish to appear with identical size
independent of the size.
School Gain (20 log R)
Fish Gain (40 log R)
School Gain (20 log
Fish Gain (40
setting
setting
338106/A