Towfish Commands; Towfish Command Set; Bottom-Tracking, Up And Down; Mute, On Or Off - C-Max CM2 User Manual

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CM2 Sidescan Sonar User Manual

8. Towfish Commands

8. TOWFISH COMMANDS

The CM2 towfish uses the same set of commands regardless of what acquisition software is being used.

Towfish start, stop, range selection and bottom-tracking control must be supported by all acquisition

software; other commands may or may not be supported. MaxView offers short-cut keys for range selection

and bottom-tracking control, as well as for towfish start and stop.

These allow the operator to force the indicated altitude to the correct value so that the altimeter can resume

lock on to the bottom. .

Mute, Off or On

Mute allows the towfish to run as normal but with no acoustic transmissions. This is useful for diagnostic

purposes where an echo sounder or other acoustic source may be interfering with the image. When muted,

indicated altitude is zero.

Shallow Mode, Off or On

Shallow mode is intended for use only in very shallow water where the user needs to use the towfish at less

than the normal altitude limit of 1.4m. In shallow mode the gain profile is started at the towfish position itself

instead of at the first bottom echo and the indicated altitude is zero.

Gain Hold, Off or On

Gain Hold allow the automatic gain to be inhibited, fixing the gain profile as it was when Gain Hold was

selected.

Normally the only reason to disable the automatic gain is if the image of a certain target, such as a wreck,

needs to be observed without the gain slowly changing. If the gain profile is held whilst the target is in view,

the reflectivity of any part of the target can be directly compared. Also if the target has a significant dark area,

holding the gain constant avoids the "gain shadow" as the scan moves back on to the relatively light

background again.

Caution: If the gain profile is held constant this automatically disables the towfish from measuring its altitude.

The reason for this is that changes in bottom reflectivity together with the fixed gain may mean that the

altimeter would have difficulty in bottom-tracking. However the altitude can still be adjusted by the operator

using the bottom-tracking, up and down controls. Also note that the correction for the shape of the acoustic

beams may be wrong if the altitude changes whilst the gain is held.

When Gain Hold is in the On state the overall gain profile can be adjusted up or down, in 1dB steps.

Version 3.6 (2008)

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