3 Choosing Range and Start Range values in a surface-related echogram

A Surface echogram is mainly used when you wish to look at the entire water column starting from the sea surface and down to the sea bottom. In a Surface echogram, the start depth of the echogram is defined by the positive Start Range depth value. The range from this start depth and down is defined by the Range value.

Context

The Range setting defines how "deep" you wish the EK80 system to detect echoes. In other words, this is the vertical distance between the "top" and the "bottom" of the echogram. The Range setting specifies the "bottom" depth, while the Start Range setting specifies the "top" depth.

The range you specify applies to the currently selected echogram. It is identified with a thick border. Several echogram types are available.

In a Surface echogram, the Start Range value is used to determine from which depth the echogram will start. This is normally a few metres below the sea surface. The Range value is then used to define the vertical extension of the echogram. The Range may be set to Auto, but for scientific purposes a fixed range is recommended. The Auto setting allows the EK80 to automatically determine the depth range based on bottom detection.

Example

Start Range in a surface-related echogram

In a surface echogram, set the Start Range value to 0 metres. This will make the echogram start from the sea surface (provided that the transducer offset has been defined). Set Range to the current depth plus 20 metres. The echogram will now show the area from the sea surface and down to 20 metres "below" the sea bottom. The sea bottom contour is easily detected when the depth changes.

Procedure

Click in the view you want to activate.

The setting you choose will only be valid for the active view. The active view is identified with a thicker border.

Observe the Main menu.

Its default location is on the right side of the display presentation.

Locate the Start Range function.

Choose a positive value for Start Range to place the top of the echogram at the preferred depth below the sea bottom.

The following methods can be used to adjust this setting:

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Select [+] or [-] to choose the level.

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Select the middle of the button and keep the mouse button pressed. Drag the cursor sideways to increase or decrease the level.

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Select the middle of the button to open the menu. Type the requested value. (You can only do this if you have computer keyboard connected to your computer.)

Locate the Range function.

Choose a positive value for Range to place the bottom of the echogram at the preferred depth over or under the sea bottom.