The choices in this menu depends on which view in the display presentation that is currently "active". The menu may therefore change from one view to another. The name of the currently active view is identified at the top of the menu. The screen capture may not show you all the menu choices.

Several of the functions offer Apply to All. If you select Apply to All your setting is applied to all the views in the current presentation mode.

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. TVG (Time Variable Gain) compensates for the loss of acoustic energy due to geometric spreading and absorption.

Ping‑Ping Filter

The Ping-Ping Filter analyses the historical information from previous consecutive pings in order to remove unwanted noise and interference from the echo presentation.

Pulse Type

The Pulse Type function allows you to select the "shape" of the transmitted pulses ("pings"). Different shapes have different qualities. Which pulse type to use depends on the current environmental conditions, your range to the target(s) and the type and speed of the target(s) you are observing.

Bandwidth

The Bandwidth function allows you to select the frequency range in the Hyperbolic Frequency Modulated (HFM) and Linear Frequency Modulated (LFM) transmissions.

Frequency

Use the Frequency function to specify the centre frequency for the frequency modulated (FM) transmissions (pings) and the operating frequency for the continuous wave (CW) pings. You can change the frequency in predefined steps from a "start frequency" to an "end frequency".

Horizontal TX Sector

In a horizontal swath the ST90 system transmits with a maximum horizontal opening angle of 360 degrees.   Use the Horizontal Tx Sector function to control the opening angle - and thus the size - of the horizontal search sector (swath). This is the physical area that is covered with each transmission ("ping").

Vertical TX Sector

The Vertical Tx Sector function is used to change the vertical opening angle in horizontal and vertical swaths.

Range Projection

The distance to a target located anywhere in the water column can be measured in two ways. This can either be the horizontal distance to the target (True), or along the tilt angle (Slant). The Range Projection function defines how this distance is measured.

AGC (Automatic Gain Control)

The AGC (Automatic Gain Control) function runs an automatic analysis of the echo strength.

RCG (Reverberation Controlled Gain)

The RCG (Reverberation Controlled Gain) function removes unwanted reverberation from the bottom and or from the sea surface. This enhances the visibility of schools. It may however also remove scattered fish from the presentation.

Target Threshold

The ST90 system provides a bottom filter to reduce the sometimes powerful echo from the seabed. This filter is useful if you try to find fish close to the bottom.A higher numerical value increases the filter efficiency and reduces the bottom echo accordingly.

Noise Filter

The Noise Filter removes unwanted acoustic noise from the display presentation. It reduces the interference from other acoustic systems (sonars and echo sounders), as well as the noise from the propellers.

Horizontal Scroll

The Horizontal Scroll function controls how fast the echoes shall travel across the Inspection view.

Vertical Reference

During operations in a vertical view you may wish to focus on the echoes in the upper or lower part of the view.Use Vertical Reference to hide a part of the view. The function is only available in the Vertical and Plane views.

Echogram

The Echogram dialog box allows you to control the echogram presentation in the Inspection views. Two pages control the horizontal lines and the echogram type with applied TVG (time variable gain). One page controls how fast the echogram travels horizontally across the presentation.

The following pages are provided:

Lines

The echo presentations in the Inspection views resemble the echograms you see on an echo sounder. The Lines page in the Echogram dialog box allows you to control the horizontal and vertical lines used in the echogram presentation. You can make the bottom easier to see, and add lines that hold additional information. The vertical scale of the echogram presentation can be changed. If you wish to add annotations to your echogram, these are enabled on this page.

Echogram

The echo presentations in the Inspection views resemble the echograms you see on an echo sounder. The Echogram page allows you to choose which type of echogram you wish to display. You can also control the TVG (Time Variable Gain). The ST90 system can work with several different TVG compensation settings. The TVG (Time Variable Gain) compensation is designed to counteract the natural phenomena of geometric spread and absorption loss.

Horizontal Axis

The echo presentations in the Inspection views resemble the echograms you see on an echo sounder. The echoes travel from right towards left across the echogram presentation. Use the Horizontal Axis to choose the horizontal scale of the echogram. This controls the "speed" of the echoes.

Information Pane Options

The ST90 system offers several information panes to provide additional and detailed data from the presentations. The information panes are opened and closed from the top bar. Several of the information panes are fitted with a Setup button. Select Setup to open the Information Pane Options dialog box. Use the Information Pane Options dialog box to change the operating parameters for the data provided in the information panes. This dialog box contains a number of pages selected from the menu on the left side.

The following pages are provided:

Size Distribution

The Size Distribution information pane presents a histogram with the echoes from single fish. The calculations are based on the fact that different fish species have different echo strength. The echo strength also depends on the operating frequency you use. Use the Size Distribution page to define the properties for the histogram shown in the Size Distribution information pane.

Fish Position

The Fish Position information pane shows the position of the detected single fish echoes. The information pane is only available when an Inspection view is "active". Use the Fish Position page to set up the presentation parameters for the Fish Position information pane.

Fish Size Adjustment

The Size Distribution information pane presents a histogram with the echoes from single fish. For various reasons, the fish sizes presented in the Size Distribution information pane may be inaccurate. Once you are able to assess your catch, you can use the Fish Size Adjustment page to change the average size of the various species.

School Mass Adjustment

When you have defined a priority target, the information in the Horizontal view includes an estimate of its area and volume. Once you are able to assess your catch, you can use the School Mass Adjustment page to change the weight/volume proportions. This will increase the accuracy of the information in the view.