Table 2.

Three main categories of underwater navigations [56].

Classifications	Principles	Methods	Characteristics
Inertial/dead reckoning	uses accelerometers and gyroscopes to estimate the current state	Magnetic compass, barometer or pressure sensor, DVL, INS	Increasing and unbounded position error
Acoustic Navigation	measuring the time of flight (TOF) of signals from acoustic beacons to perform navigate	LBL, UBL, USBL	Depending on beacons
Geophysical Navigation	use external environmental information as references for navigation	Magnetic field maps, visual-based seabed images, identify feature acoustically	Depending on sensors to identify environmental features