4 Choosing the depth range and the start depth for the echograms

In each echogram, the start depth is defined by the Start Range depth value. This is the "upper limit" of the echogram. 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 way the Range and Start Range settings work depends on the echogram type.

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Surface: 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.

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Bottom: A Bottom echogram is mainly used when you want to examine the echoes from fish close to the sea bottom.

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Pelagic: A Pelagic echogram is mainly used when you wish to look at the water column starting from any distance below the sea surface down towards the bottom, but without seeing the bottom contour.

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Trawl: The Trawl echogram covers the vertical opening of the trawl with reference to the depth of the headrope.

Procedure

Observe the Main menu.

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

Locate the Start Range function.

Make the necessary adjustment.

The following methods can be used to adjust this setting:

Select [+] or [-] to choose the requested setting.

Place the cursor on the button. Press and hold the left mouse button. Move the cursor horizontally over the button. Release the mouse button when requested value is shown.

Select the middle of the button to open it. If you have a keyboard connected to the EK80 system, type the requested value.

Locate the Range function.

Make the necessary adjustment.

The following methods can be used to adjust this setting:

Select [+] or [-] to choose the requested setting.

Place the cursor on the button. Press and hold the left mouse button. Move the cursor horizontally over the button. Release the mouse button when requested value is shown.

Select the middle of the button to open it. If you have a keyboard connected to the EK80 system, type the requested value.

Example

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.

In a bottom echogram, set the Start Range value to –5 metres. This will make the echogram start from 5 metres above the sea bottom. Set Range to the 5 metres plus 10 = 15 metres. The echogram will now show the area from 5 metres above the depth, and down to 10 meters "below" the sea bottom. The sea bottom contour will appear as a flat line.