Layer Properties dialog box
Layers are used to calculate various values for a specific range in the water column. The calculated values can be displayed in the Numerical information field. All single target detections which are displayed in the Single Target Position information field and the Single Target Histogram information field are detected within a layer. The Layer Properties dialog box is used to change the current properties of the chosen ("active") depth layer.
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Prerequisites
To use the Layer Properties dialog box you must first select a depth layer in the Numerical information field (by clicking on the layer or in the the echogram.
How to open
The Layer Properties dialog box is located on the shortcut menus and on the Active menu.
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Description
Different species often occupy different depth layers. Such layers may be defined by salinity or temperature, or simply by ambient light or the availability of food. In order to study these species, the ME70 supports a Layer function. By means of this function, you can create your own depth layers in the water column to improve the dynamic data required for analysis.
Layers are used to calculate various values from the echo data collected within a specific depth range in the water column.
Once you create your own layer, all calculated values from this layer are displayed in the Numerical information field. When the layer is selected (“activated”) in the Numerical information field (layer data shown with red text) or in echogram, all data shown by the relevant information fields are calculated values from the echo data within the selected layer.
Tip
To create a new layer, use the New Layer dialog box.
To delete a layer, select it in the echogram or in the Numerical information field (layer data shown with red text), and then click Delete Layer.
The Numerical information field is the best tool for controlling your depth layers. All layers are listed, even those that may be located outside your current echogram presentation. The different layers can easily be activated by clicking the list of numerical data.
Details
Limits
Use these settings to control the upper boundary (start depth) and the range of the depth layer.
•  Start Relative Surface
When a Surface or Pelagic layer is chosen, this setting controls the depth at the upper boundary of the layer relative to the surface depth.
•  Start Relative Bottom
When a Bottom layer is chosen, this setting controls the depth at the upper boundary of the layer relative to the bottom.
•  Range
This parameter controls the vertical depth range for the layer. Positive values are always downwards. A start range relative to bottom of for example -10 m means 10 m above the bottom.
Tip
You can also change these settings by selecting the border line and drag them up and down.
Layer Type
You can choose from three different layer types.
•  Surface
The range settings for the layer are referenced to the surface. The layer is downwards limited by the detected bottom depth if this value is shallower than the specified lower range limit for the layer. "Pings" without a bottom detection are ignored in the calculations.
•  Pelagic
The range settings for the layer are referenced to the surface. The layer is not downwards limited by the detected bottom depth.
•  Bottom
The range settings for the layer are referenced to the bottom. The layer is downwards limited by the detected bottom depth.
Integration
•  Targets Integration
This value can be used to get an idea of how much of the biomass has been detected as single targets, compared with the normal integration (sA). Check this box to calculate integration values based on single target detections.
•  Bottom Margin
When you set up the ME70 to measure and calculate echoes from the water column, the bottom echo must be avoided. The strength of this echo will greatly influence the other acoustic measurements. Use the Bottom Margin option to define a vertical depth segment above the detected bottom echo. The data in this segment will not be included in the calculations.
•  Sv Threshold
The Sv Threshold option is a filter. It will remove the weakest echoes from the calculations the ME70 do.
Example
If you are bothered by plankton while investigating other species with higher target strength, use the Sv Threshold option to remove the plankton echoes.