Layers
The Layers heading in the Numerical field contains acoustic data related to the layers defined and used in the echogram. Active Region marks the layer which is currently active. The acoustic data is written in red to signal this is the current, active layer.
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Description
The following information is provided under the Layers heading.
•  Echogram
This identifies the echogram type in use.
•  Minimum/Maximum Range
These parameters identify the depth range covered by the layer.
•  sA: sA is the nautical area scattering coefficient. sA is commonly abbreviated as NASC. In this context the sA value presents the current biomass index.
•  Sv Treshold
This is called the scattering-strength parameter for volume and is measured in dB. The scattering strength is used for enhancing the incident wave or echo beam.
•  Number of targets
This information identifies the number of individual targets (single fish) in the depth layer.
•  Max TS in ping ... at depth
These parameters identify the strongest target strength detected, and at which depth.
•  Alongship angle / Athwartship angle
These parameters identify the alongship and athwartship offset angles for the transducer. These offset angles are taken from the calibration results. These parameters refer to the angle/direction of the Max TS in ping.