Kongsberg Simrad ST90, Reference Manual

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Description
Each Inspection view offered by the
ST90 system can show you a different
echogram type. Which type to see is
chosen on this
Echogram
page. The page
also allows you to select which TVG
curve to use for the chosen echogram.
The changes you make are by default
only valid for the active
Inspection view.
Click in the Inspection view to activate it. The active view is identified with a thicker border.
Tip
You can also select TVG setting with the
TVG
function. The
TVG
(Time Variable Gain)
function is located on the
Active
menu.
Details
TVG (Time Variable Gain)
When an acoustic pulse is sent through the water, it will gradually lose its energy.
The greater the distance between the transducer and the target(s), the greater the loss
of energy.
The TVG (Time Variable Gain) compensation is designed to counteract the natural
phenomena of geometric spread and absorption loss. The TVG compensation is
expressed as a logarithmic curve. You can choose from a selection of curves. Each
curve has a different slope creating a different gain compensation.
Select the
TVG
setting you want to use. Several TVG compensation settings are
available.
•
No TVG
: TVG compensation is not implemented. This option is hardly ever used.
•
School (20 log R)
: This setting offers weaker amplification close to the bottom. It
has been designed to provide the best echoes for schools. The physical size of a
school allows you to detect it even with reduced gain.
•
Fish (40 log R)
: This setting offers larger amplification closer to the bottom. It has
been designed to provide the best echoes from single fish.
•
Targets (40 log R)
: This setting uses the same TVG compensation as Fish (40 log R) ,
but additional filtering and compensation is implemented.
Only echoes detected and interpreted as single fish are shown. The echoes are
compensated for their physical position in the beam (beam compensation). This
Functions and dialog boxes