Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. An Underwater Acoustic Positioning System is a system for the tracking and navigation of underwater vehicles or divers by means of acoustic distance and/or direction measurements, and subsequent position triangulation. Underwater Acoustic Positioning Systems are commonly used in a wide variety of underwater work, including oil and gas exploration, ocean sciences, salvage operations, marine archaeology, law enforcement and military activities.