The International Maritime Organization (IMO) aims
to ameliorate human element management in the
shipping industry. The empirical evidence and
accident data point towards the impact of human error
in maritime accidents and most shipping failures,
including collisions, allisions and groundings. An
analysis of accident data from Australia, Canada,
Norway, and the UK revealed that despite the overall
reduction of maritime accidents, human error
remained the main reason behind them in up to 80-85%
of all cases, or even 96% [2, 3]. Likewise, the Japan P&I
Club considers human error as the primary factor in
84% of 1,390 cases of maritime accidents [4], regardless
of advances in marine technology contributing to
reducing the frequency and severity of marine
accidents [5].
This paper aims to assess the current and future
technology used for navigational purposes, the
advantages and disadvantages of autonomous vessels,
and the importance of the human element in future
navigational technology and reach conclusions
regarding our proximity to the era of industry-wide
autonomous navigation.
2.1 The Radar
The name "Radio Detection & Ranging" (RADAR)
comes from the initials of the English phrase RADAR.
This means "detection and range of electromagnetic
waves". As the name suggests, the operation of radar is
based on electromagnetic waves, and according to Gao
et al. (2022), in particular, the distance determination is
based on a time measurement from the point when the
electromagnetic wave pulse is emitted to the returning
echo, the waves ultimately representing the detectable
object) [6]. Also, the Radar uses a rotating antenna to
determine the direction it emits and emits pulses of
A Theoretical Analysis of Contemporary Vessel
Navigational Systems: Assessing the Future Role of the
Human Element for Unmanned Vessels
D. Polemis
, E.F. Darousos
& M. Boviatsis
University of Piraeus, Piraeus, Greece
World Maritime University, Malmoe, Sweden
ABSTRACT: This article aims to investigate the contemporary challenges of electronic navigation and assess the
appropriate amendments should autonomous vessel technology becomes widespread in the near future. Vessel
control systems and maritime communication are essential and sending and receiving alarm signals is critical to
contemporary ship navigation. Numerous location and shipping information systems, such as GPS, Loran-C, and
Decca, have arisen in recent decades to improve navigational safety. Other systems, including VHF and Inmarsat,
have been developed to enhance the efficiency of maritime communication on board and to transmit risk and
safety-related data. Additionally, safe navigation requires systems like Navtex, EGS, DSC, Epirb, and others [1].
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 16
Number 4
December 2022
DOI: 10.12716/1001.16.04.05
electromagnetic waves in the form of a beam of light. It
also receives an echo back to it [7].
Today, depending on their use, the main types of
radars relevant to the shipping industry are as follows
Surface detection radar or navigation
Air detection radar
Meteorological radars
Fire control radar
Radar speed measurement
2.1.1 Surface detection radar or navigation
Surface detection radars or navigation radars are
installed on the coast or on vessels to detect the surface
of the sea. However, they can also detect airspace, but
at minimal heights. Instead, they detect solid objects
from relatively conductive material at sea level or low
altitudes and provide accurate information about the
distance and view of the target they locate. Precise
detection is possible regardless of the visibility
conditions and at distances more significant than the
visible horizon [9].
2.1.2 Air detection radar
Placed on the ground (near mountain peaks or
airfields) and boats, they explore long-distance and
high-altitude airspace. The air detection radar ensures
air traffic control to ensure the direction of the aircraft
and the detection of enemy aircraft from long
2.1.3 Meteorological radars
These weather radars ensure the timely detection
and monitoring of upcoming storms and cyclones.
2.1.4 Fire control radar
Part of various weapon systems, they provide the
necessary launch elements and even corrective
elements for the direction of certain types of remote-
controlled projectiles.
2.1.5 Radar speed measurement
Used to accurately measure the speed of ships in sea
areas where speed limits apply [10].
3.1 The ARPA System
Obligations in Article 7(b) and other relevant
provisions of the International Collision Avoidance
Code refer to the observation of targets on a bridge
deck or further corresponding systematic observation,
performed via an automated printing system called
automatic radar protection equipment (ARPA) [11, 12].
Current technology, especially in cases of multiple
targets and situations of limited visibility, can lead to
limited monitoring, an issue expected to be solved
through ARPA. Many targets are accomplished with
the help of the Automatic Radar Plotting Aid (ARPA),
including reducing the minimum effort required to
obtain more target information displayed on the radar
screen. Also, the ability to evaluate situations
accurately and continuously as the ARPA
microcomputer equipment receives information on the
target area and line of sight for radar equipment. Plus,
the course and speed of the nearing vessels vessel are
combined for sublimation, specifically the Closest
Point of Approach (CPA) and the Time of the Closest
Point of Approach (TCPA) in which the target will
pass, giving the navigators the target's direction and
speed the direction and speed of the target. The ARPA
range is 16 nautical miles [13, 14].
3.2 The Gyroscopic Compass
The gyroscope is an instrument rotating around an
axis, passing through its centre. Solids are rotary and
symmetrical around this axis. Initially conceived by
Foucault in 1851) and with the first gyroscopic compass
constructed in 1908, the gyroscopic inertia proves that
the Earth revolves around its axis [15].
Regardless of its specific subtype, each
contemporary gyroscope requires frictionless action
for one or two gyroscopic flywheels that are part of a
three-phase motor. In addition, of course, the engine
must have a unique power supply to rotate. A suitable
control system is also necessary so that their axis of
rotation or the component of the axis of rotation of a
gyroscope or two gyroscopes looks for the meridian
direction of the site. Finally, there must be a sufficient
power transmission system, which the instructions of
the wind turbine of the main compass to be electrically
transmitted to their wind turbines repeatedly via an
electrical supply [16].
3.3 Free gyroscope and its properties
A free gyroscope consists of a torsional mass, most of
which is distributed on its periphery and is thin and
balanced. The clamp has 3 degrees of freedom; that is,
it can move three axes freely around its axis of rotation,
the horizontal axis and the vertical axis. This is
achieved by using the correct suspension. When the
free gyroscope rotates around its axis, the gyroscopic
inertia and transition are received, with the former
being the free gyroscope that retains its properties. The
transition is the property of the gyroscope. As a result,
if a particular force is applied to the free gyroscope, a
specific force will cause the axis of rotation of the
moving gyroscope. Thus, the free gyroscope will
become a controlled gyroscope, free for a short time yet
controlled upon using the compasses. There are two
methods for the free gyroscope to turn the Compass
gyroscope: The Sperry method, with a northern part of
the gyroscope and the Anschutz method, with weight
at the bottom of a system of two round flywheels [17].
3.4 Gyroscopic compass errors
A regular series of inspections are needed to avoid
multiple errors associated with the gyroscopic
compass, including the (a) error of navigation,
direction, and velocity, (b) depreciation error, (c)
ballistic diversion error and (d) ship wall fault. The
inspections include comparison with magnetic
compass indications at least daily and checking the
accuracy of the observations on the ground objects or
celestial bodies [16].
4.1 Radiogoniometer properties
A Radio Direction Finder direction detector (RDF) is
the oldest radio navigation aid used to identify the
address of the station to which the received
transmission was sent to the receiver of the device's
signal. The basic principle of operation of a
radiogoniometer is based on its antenna characteristics,
providing the receiver with a variable power signal
depending on the direction from which the signal
reaches the transmitter. The simplest radiogoniometer
antenna is a simple loop or frame antenna, which may
have a circular shape, rectangle, triangle, etc. [18].
4.2 Radiogoniometer errors
Under ideal viewing conditions, the radiogoniometer
can be highly accurate. However, this is often not the
case. Indicatively, when the recipient determines the
address from which he receives the transmitter’s signal
(beacon, ship, etc.), it is usually not the same as the
corresponding signal. This difference is due to several
factors affecting radio wave propagation and
producing deviations from their regular route. These
factors contribute to various errors in the
radiogoniometer. They are errors due to meridians,
polarities or nocturnal effects, coastal refraction or its
effects due to ship bugs and square error, semicircle
error, total error and radiogoniometer calibration [19].
5.1 Automatic rudder
Autopilot is an advanced electromechanical and
electronic system. It is connected to the gyroscopic
transmission system through ship repeaters to know
that the ship deviates from its steady course, and with
a turn of the rudder blade, the vessel may return to its
course. An alternative automatic rudder also exists,
which uses separate magnets and a compass to
automatically follow the correct route in case of a
vessel’s gyroscopic compass failure [20].
5.2 Automatic rudder function
When the ship leaves its course, the sailor must turn his
steering wheel to the opposite to reestablish the
system. This depends on how many times the number
of degrees the ship is off course has, so it should be
placed at a right angle. Its rudder is usually small
enough to bring the boat back into orbit. On its bridge
is a deck control unit in which a repeater (relay motor)
is operated by a gyroscopic compass on board,
activating the entire autopilot mechanism [21].
5.3 Double unit rudders
Transmission of electrical signals from the deck control
unit to the steering wheel of a double unit to the power
unit of the stern turns into a mechanical or hydraulic
drive. Of course, one should follow the operating
schedule as accurately as possible. The stresses of the
ship, the rudder, the automatic rudder, and the
automatic rudder must also be reduced. This also
depends, of course, on the sea conditions and the
towing capacity of the vessel. Finally, the autopilot is
nowadays equipped with a computer unit that can
plan the entire trip and automatically performs the
required course changes during this time [22].
6.1 The sonar technology
The sonar is an electronic naval instrument that
informs sailors of the ocean’s depth under a ship’s keel.
The operation of the device is based on the emission of
sound waves under the keel perpendicular to the
bottom. The emitted sound waves travel to the bottom,
face it, and then are absorbed, diffused or reflected in
different directions. Most of the reflected sound energy
will return to the source as an echo. With a properly
programmed operating cycle, an audio device changes
its operation from an audio transmitter to a receiver.
The device accurately measures the time elapsed
between the onset of a sound wave and its reflection is
received and determines the depth of the sea by
calculating the speed-space-time ratio [23].
6.2 Principe of operation of sound instruments
The operation of the sonar is based on the constant
speed at which it moves. Ultrasonic waves in seawater
where their reflections when they hit the seabed or
other solid objects from which they return to the
reflected waves form echoes. Unique grooves in the
area of the keel are in place to prevent its destruction.
At the same time, a particular oscillator has been
installed that can receive pulses and ultrasonic waves
of high power of a very short duration perpendicular
to the bottom. Part of the energy of each ultrasonic
pulse as it hits the bottom is also reflected in the form
of echoes at the same frequency as the ultrasonic pulse
returning to its keel and being taken from another
sensitive oscillator. After the frequency propagation,
the time from the launch time to the launch time of the
ultrasonic wave is constant, but the return time is also
constant from projection time to projection time. The
return corresponding to each echo pulse will be
proportional to twice the distance from the ship's keel.
The propagation rate of ultrasonic waves is constant
Loran-C is a long-range positioning system whose
position lines are determined by time difference
measurement and phase comparison. The location of
the corresponding chain is used to determine the
location in the zone. A Loran-C station chain consists
of a primary station, M and two, three or four
secondary stations denoted by the letters X, Y, Z and
W, which are located around the central station in the
centre of the area. Each station emits a long-distance
pulse signal at a frequency of 100 kHz. To determine
the position, the system receiver on board measures the
time difference it receives from the central station. Each
master-slave station determines the position line above
and the ship's position by the intersection of the two
unnecessary position lines. In practice, the seafarer
identifies the Loran-C position in one of the ways: by
using unique Loran-C maps on which the excessive
position lines corresponding to the measured time
differences are drawn, or by measuring matrices, or
even directly by the indications of width and length
provided by certain modern receivers [25,26].
The points identified by the Loran-C system are
some that are divided into systematic and random.
According to some physicists, systematic errors or
mathematical laws lead to the same result in all
measurementserrors due to the Loran-C signal
propagating on land [27].
Random errors due to unbalanced factors are
generated, and it is not accidental since they are not
even observed, so it is impossible to calculate the
corresponding correction [28].
The Global Position System (GPS) system is a second-
generation satellite system. Its development began in
the early 1970s and was completed between 1992 and
1995. It can give sequentially to any area on Earth (a)
High precision placement in three dimensions (width,
length and height of the sea ) (b) Accurate World Time
U.T.C. (c) Ship speed data [29].
GPS positioning is based on the measurement of the
distance of the receiver from three satellites whose
positions are determined at the intersection of three
spheres focused on the position of the satellite, with the
measured distance as a radius, accurately identifying
the location of any part of the earth. The computer
which controls and coordinates all the functions of the
receiver shall be selected by the most appropriate
available satellite, applying corrections, and
calculating the position and speed as well as the
location of the vessel and the dispersion to be followed
to reach the destination and the distance from the given
point [30].
9.1 Introduction to autonomous vessels
Maritime transportation faces tremendous challenges
in our time, such as a significant increase in transport,
environmental and institutional requirements, and
expected reductions in human resources. The
development of technology led to the development of
new navigation equipment solutions, a gradually but
steadily advancing wave of automation. This
development may improve shipping operations by
promoting the adoption of a more sustainable mode of
navigation by reducing the time of seafarers’ onboard
engagement and the subsequent elimination of
seafarer fatigue, stress, and errors [31].
The terms "autonomous" and "unmanned" can be
used several times to identify the same thing. At this
point, it would be reasonable to give the full definition
of the above words. Referring to the word
"autonomous", we explain that the ship can then carry
out some defined operations with little or no care by
the guard officers of the bridge. It does not close the
possibility that there may be a human being. Contrary
to the term "unmanned", we mean that there is no one
in the cockpit of the bridge to supervise any action.
Apart from that, however, the crew may still be on
board. With the term " Maritime Autonomous Surface
Ship " (MASS), it has already been proposed by the
IMO to characterise as a term an autonomous ship.
MASS was established as "ships which have varying
degrees of autonomy and can operate independently of
human interaction" [32].
The Maritime Unmanned Navigation through
Intelligence in Network (MUNIN) organisation carried
out a preliminary Conception and Research for the
Implementation of Unmanned Ships in the shipping
industry; however, several difficulties and doubts
prevent unmanned ships from being widely adopted
by the industry, involving, indicatively, loss of control
while the ship is at sea, accidental damage to the ship
and during the voyage, and insufficient monitoring in
dangerous areas [33].
The absence of a human element is not the only
difference between traditional and autonomous ships.
An essential difference between the two is the
formulation, management and implementation of
individual decisions made by the crew and the master
on conventional ships. Unmanned ships can be
achieved through a combination of remote, automatic
and autonomous control, according to the IMO [34].
An autonomous vessel is a vessel controlled by
automated systems for navigation, including its
engine. These systems will be pre-programmed as we
can now have a pilot who follows the prescribed route
plans. However, autonomous ships are not necessarily
uncrewed. The maintenance team may be involved
during the voyage to maintain or repair systems on
board, as described above, where ships are expected to
be manned as they approach and leave the port. A
reliable communication system will be one of the
challenges of the system; if the autonomous systems
cannot cope, such systems will be retained as a last
resort. An increase in autonomy is expected to reduce
the need for the crew on board [35].
The IMO proposed the following four degrees of
autonomy [32, 36]:
Ship with automated processes and advanced
decision-making functions. The crew should be on
board and control and operate all its systems and
Remotely operated ship with a crew on board. The
ship is controlled and operated from some remote
location, but the crew is still on board.
Remote-controlled ship without crew on board. The
ship is controlled and operated from some remote
location, with no crew on board.
Fully autonomous ship. The ship's operating
system can make decisions and handle all situations
without human intervention.
9.2 The importance of technology for autonomous vessels
Recently, the strengthening of satellite
communications and the continuous improvement of
other transport aids/systems, such as the AIS, The
GMDSS Risk and High Identification and Monitoring
System, or the scope of LRIT, is a reality. All these
have laid the technical foundations for the
advancement of the shipping industry, being strongly
related to its group of remote-controlled ships.
Therefore, the concept of unmanned vessels presents
many vital concepts, such as advantages in the design
and construction of ships, in the reduction in operating
costs such as fuel and labour and, finally, the
environmental impact associated with conventional
vessels. However, the implementation of such
autonomous systems focuses on long-distance
commercial maritime transportation and is still limited
to passenger vessels. Naturally, the autonomous
operation of unmanned ships requires as much
possible navigation and control with high reliability,
error detection and a high safety rate [37].
This requirement, however, includes an inherent
need to provide basic information such as the position
of the ship in real time to avoid allisions and collisions
with other vessels or other obstacles. Contemporary
technology offers automatic collision avoidance and
critical reconnaissance systems, sensors such as radars
and cameras to identify and sweep the vessel’s
environment, and sea navigation and support for
passenger services [38].
Future needs must also focus on the interaction
between manned and unmanned vessels and
autonomous ship control centres. The IMO defines
electronic navigation as a unified collection, integrity,
exchange, visibility and separate analysis of marine
information on board and on land by electronic means
to improve navigation, anchorage and improvement
services responsible for safety and development,
marine protection and protection of the marine
environment. The international conventions lay down
rules for the prevention of collisions with ships and
regulations for the prevention of maritime collisions,
the so-called COLREGS by the International Maritime
Organization IMO. While the COLREGS Convention
mainly focuses on manned vessels, the main objective
is that these regulations also apply to automation
regulations and s