Attack_angle is an analysis export variable available in exported integration analyses when the schools detection module is licensed.
It reports the attack angle of a school represented by a region on an echogram (degrees), as defined by Diner (1998).
Diner defines the attack angle as the angle between a vertical line, from the transducer, and another line, towards the school edge, measured at the moment when the school detection is just beginning. This happens when the number of fish, within the acoustic beam, is high enough to produce an echo signal amplitude just above the processing threshold.
See Schools detection module algorithms for a mathematical definition.
This variable is exported only if it is selected on the Export page of the EV File Properties dialog box.
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Schools detection module algorithms