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You should read manual:

Towed Array Contacts

Because of the way the physics of the towed array construction, an ambiguous contact, a mirror image of each true contact, appears on the display along with the true contact. If you have a contact at the same bearing on your bow array, you can be fairly certain a contact at a bearing on your towed array display is on contact’s true bearing.
If the contact is not visible on another array, changing the course of Ownship allows you to determine which bearing is the actual and which is its mirror image on the display. After you maneuver, one contact remains at a consistent bearing and one appears to move in the display. The contact’s true bearing is that of the contact that remains constant.
When numerous contacts are present or the contacts are close together, this process can be very challenging!