133
1 INTRODUCTION
About 80% of ship collision is reported to be caused
by human error. And most of this human error is
"lack of situational awareness". One of the methods to
prevent the collision caused by the "lack of situational
awareness" is the adoption of a system that constantly
grasps the level of collision risk with vessels
encountered and assists in selecting the optimal
method of collision avoidance manoeuvring.
Therefore, the authors developed an automatic
collision avoidance system that helps prevent human
error. Several researches have been done on automatic
collision avoidance system [1],[4],[5]. The system
developed by the authors is a system constantly
calculating optimal manoeuvring method from the
risk and economic preference in the ship
manoeuvring space where the course change and the
deceleration are performed. The system basically
takes actions according to the International
Regulations on the preventing collision at the sea
(COLREGs) and also considers the manoeuvrability of
the ship. In order to verify the effectiveness of this
system, many verification experiments were
conducted using a full mission simulator. And
experiments were also successfully conducted to
verify the effectiveness of the proposed automatic
collision avoidance system on the actual ship
navigating in congested waters. It was verified by this
verification experiment on an actual ship that it was a
practical level as a collision avoidance support
system. This system is not limited to the collision
avoidance support system, and in the future, it is one
of the extremely effective elemental technologies as an
automatic collision avoidance system to be installed
on unmanned autonomous ship.
In addition, the authors proposed a method to
quantitatively evaluate the collision avoidance
manoeuvring results. Using this evaluation method,
Development o
f
Automatic Collision Avoidance System
and Quantitative Evaluation of the Manoeuvring
Results
S. Nakamura & N. Okada
J
apan Marine Science Inc., Kawasaki, Japan
ABSTRACT: The automatic collision avoidance system introduced in this paper is a system constantly
calculating optimal manoeuvring method from the risk and economic preference in the ship manoeuvring
space where the course change and the deceleration are performed. The authors also propose a system that
quantitatively evaluates the collision avoidance manoeuvring results. Based on the evaluation results of this
system, the authors are setting parameters so that ship manoeuvring that does not give anxiety to target ships
to be avoided is also realized in automatic collision avoidance manoeuvring. In addition, comparison between
the manoeuvring results of the automatic collision avoidance system and the veteran captain's manoeuvring
results was quantitatively compared by the proposed evaluation system. Verification experiments were
successfully conducted to verify the effectiveness of the proposed automatic collision avoidance system on the
actual ship navigating in congested waters.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 13
Number 1
March 2019
DOI: 10.12716/1001.13.01.13
134
we have compared the results of the automatic
collision avoidance system with the results of ship
manoeuvres by humans, and based on these
evaluation results, we confirmed that the automatic
collision avoidance system performs manoeuvres
equal to or better than veteran captains.
Furthermore, the authors point out that it is
important to conduct manoeuvring in which the
manoeuvring by the automatic collision avoidance
system does not give anxiety to other ships in the sea
area where the ships manoeuvred by humans and
ships manoeuvred by the automatic collision
avoidance system coexist. The developed automatic
collision avoidance system objectively verified that it
did not give anxiety to other ships.
2 CONCEPT OF AUTOMATIC COLLISION
AVOIDANCE MANOEUVRING
2.1 Strategic Collision Avoidance Manoeuvring
The authors developed an automatic collision
avoidance system considering the realization of
strategic collision avoidance manoeuvring. Strategic
collision avoidance manoeuvring means ship
manoeuvring which minimizes the economic loss,
constantly selects a low-risk course from an early
stage and reduces the encounter situation where the
manoeuvring load is high. General ship navigator
selects avoidance manoeuvring method in
consideration of avoiding the risk of collision and
minimizing economic loss. However, there are
individual differences in the collision avoidance
method. The method of collision avoidance
manoeuvring is not uniform, such as a method of
choosing to alter her course drastically after the risk of
collision becomes prominent, or a method of slightly
altering her course before rules defined by CORLEGs
is applied. The automatic collision avoidance system
for realizing the strategic collision avoidance
manoeuvring proposed by the authors is based on the
latter manoeuvring.
2.2 Calculation of Collision Risk and Preference in the
Collision Avoidance Manoeuvring Space[3]
When a navigator decides the method to prevent a
collision, two principal requisites should be
considered. One is the risk of collision and other is the
economic loss of voyage. These two factors conflict
with each other and have a different dimension,
however both factors can be assessed on the same
plane by using the collision avoidance manoeuvring
space concept. Figure 1 shows the collision avoidance
manoeuvring space model (X
i, j). The horizontal axis is
a course (i), the longitudinal axis is a speed (j) and the
evaluation value of each manoeuvre (Pb(X
i,j)) is
extended perpendicularly upward. In the collision
avoidance manoeuvring space, the evaluation value
for each ship manoeuvring method is calculated from
the collision risk and the economic preference. The
shape of a figure like a roof in the Figure 1 shows one
model of preference order as expressing a general
tendency with exponential function. The model of
preference order is expressed as follows;
,0
0,
,,00,
ic
jv
ij i j
Pb X exp a Co
Pb X exp a V
Pb X Pb X Pb X
(1)
where, Pb(X
i, j) is evaluation value of preference of
manoeuvre X
i, j, ∆Co is degree of altering course, ∆V is
ratio of reduction speed, a
c and av are the coefficient to
calculate the preference order. In this figure, the
evaluation value is highest for maintaining the
present course and the present speed. Altering the
course to the starboard is higher than altering the
course to the port. According to this preference
model, as a method of avoidance manoeuvre, first,
altering the course to the starboard is given priority at
the present speed.
Preference evaluate value
P
b
(
X
i
,j
)
: 0 to 1.0
Model of Preference order
Collision Avoidance
Manoeuvring Space
Present Speed
Present Course
Stop
Pb(X
i,j
)
Figure 1. The collision avoidance manoeuvring space, and
one model of preference order as expressing a general
tendency: Pb(X
i,j)
b
d
a
c
D
i
s
t
a
n
c
e
D
i
r
e
c
t
i
o
n
o
f
R
e
l
a
t
i
v
e
M
o
v
e
m
e
n
t
Vt
Own Ship
V
o
Vt
Rv
Relative y-axix
Relative x-axix
Abusolute X-axix
Abusolute X-axix
Ryk
Rxk
1.0
1.0
Target Ship
衝突危険度を表す関数
衝突危険度を表す関数
X
t
Y
t
X
o
Y
o
Function indicating collision risk
Function indicating collision risk
Y
Rx
Ry
Figure 2. The basic idea how to calculate the collision risk
by using exclusive area
135
𝑅𝑎𝑣 =
(
𝐴∙𝑉
𝑅
+𝐵
∙
𝐿
𝑜
2
+𝐿
𝑡
2
2
(3)
Rav : Risk calculation starting distance
VR : Relative speed (m/s)
Lo : Own ship LOA (m)
Lt : Target ship LOA (m)
A, B : Coefficient
r : Coefficient (𝑟 ≒
𝑅𝑎𝑣
3
)
𝜃 : 45 degree
θ
r
Rav
𝑉
V
R
Own Ship
Tar
g
et Ship
Rav
(m)
Figure 3. Risk calculation starting distance
Figure 2 shows the basic idea how to calculate the
collision risk by using exclusive area which is shown
as an ellipse. The size and location of this ellipse (a, b,
c, d,) were defined by summarizing the results of
statistical studies that had been done by the authors
[2],[3].
The area where the risk calculation is performed is
determined by the size and relative speed of the ship
as shown in Figure 3. Taking into account the
COLREGs, to calculate the risk of the ship seen on her
starboard at an early stage, the ship's position is
shifted by a distance r. The risk of collision was
defined as followings.
,
,1
ij x y
Tcpa
RX MaxR R
Wtcpa
(2)
In above equation, Ry means the risk in direction
of the fore and aft line of a target ship, and Rx means
such as the transverse direction. Then the larger one
was adopted as the risk of collision on such
manoeuvre; X
i, j. (Rx, Ry; 0: No risk, 1: Maximum risk).
And further, a margin of Time to Closest Point to
Approach (Tcpa) was considered as a ratio of type to a
certain constant time; Wtcpa. Figure 4 shows the
degree of risk in the collision avoidance manoeuvring
space when there is a crossing situation with a target
ship.
2.3 Model of Automatic Collision Avoidance
Manoeuvring [3]
In the automatic collision avoidance system, the
preference evaluation function for selecting the
manoeuvring method is defined by the following
equation from the risk shown in Figure 4 and the
preference shown in Figure 1. The meaning of this
equation is to subtract Figure 1 to Figure 4.
., ,
1,
max
Ij ij ij
km
Ev X Pb X R X
(4)
Risk evaluation value
R(X
i,j
): 0 to 1.0
Risk degree distribution
Present Course
Present Course
Stop
Present Speed
Own Ship
LOA:170m, 12kts
Target Ship
LOA:150m, 12kts
Figure 4. The degree of risk in the collision avoidance
manoeuvring space when there is a crossing situation with a
target ship: max{R(X
i,j)}
Own Ship
LOA:170m, 12kts
Target Ship
LOA:150m, 12kts
Figure 5. Distribution chart of the preference evaluation
index of each manoeuvre: Ev(X
i,j)
The second term of a right side means that the
maximum risk value of targets in encounter situation
(the number of vessels k=1 to m) and α is a coefficient
to adjust the relation between a preference and a risk.
According to the definitions mentioned above,
distribution chart of the preference evaluation index
of each manoeuvre are shown in Figure 5. This Figure
136
5 is obtained by subtracting Figure 1 to Figure 4 in the
manoeuvring space according to the expression (4).
(Here, α = 1)
In the automatic collision avoidance system, the
manoeuvring method X
i, j having the highest
preference evaluation index Ev(X
i, j) is selected. In the
example in Figure 5, it is altering course 18 degrees to
starboard at the present speed. Although detailed
description is omitted here, other matters considered
in this system are briefly described below. The
manoeuvrability of the ship is taken into
consideration in the risk calculation process. Also,
when directing the course to the next waypoint, it is
considered in the calculation process of the preference
of the manoeuvring method.
3 EVALUATION METHOD OF COLLISION
AVOIDANCE MANOEUVRING RESULTS [2]
According to the research by the authors, the main
factors for the navigator to recognize the risk of
collision with other ships are the relative distance
between the own ship and other ships, the rate of
change in bearing, the bow crossing, the stern
crossing, and the crossing direction. Therefore, the
authors propose a method of defining "Danger area",
"Caution area", "Safety area" with relative distance
and bearing change rate shown in Figure 6 as an
index for evaluating the collision avoidance
manoeuvring result. In order to create this area, it was
formulated in an experiment with a simulator in
which 12 Captains and Pilots participated.
Experiments were conducted using 135 encounter
scenarios and formulated from the results. The total
number of data reaches approximately 30,000 points.
For the evaluation of the collision avoidance
manoeuvring result, calculate it as ‘-2’ for weighting
coefficient when the ship enters 'Dangerous area', ‘-1’
for 'Caution area', ‘0’ for 'safety area'. Specifically, it is
expressed by the following expression.
0
21
100
end
t
tt
t
end
Dangerous Cautionary
Score
t
(5)
where
Score: Evaluation score (Deduction point) 0 points if
there is no danger, minus points increase if many
dangerous situations occur.
Dangerous
t: Period/time that existed in the danger
area (sec.)
Cautionary
t: Period/time that existed in the caution
area (sec.)
t
end: Period/time of ship manoeuvring (sec.)
[Head-on / Crossing Situation] [Same-way Situation]
Bow Crossing
Stern Crossing
Safety
CautionDanger
Bea ring Changing rate [deg./min.]
Bea ring Changing rate [deg./min.]
Safety
Safety
Caution
Caution
Danger
Dist. [Miles]
Dist. [Miles]
Figure 6. The evaluation area diagram (The “Danger area”,
“Caution area”, and “Safety area” defined by the relative
distance and rate of change of the bearings)
4 PARAMETER SETTING FOR CONDUCTING
AUTOMATIC COLLISION AVOIDANCE
MANOEUVRING THAT DOES NOT GIVE
ANXIETY TO THE TARGET SHIP
The manoeuvring method using the automatic
collision avoidance system developed this time is
depend on the parameters set in Figure 1 to 3 and
Equations 1 to 3 etc. These parameters are basically
set as a function of the degree of BC: Blocking
Coefficient that represents the degree of congestion
[3]. The authors point out that it is important not to
give anxiety to the target ship to be avoided in setting
parameters. In order not to give anxiety to target
vessels, it can be rephrased as not to enter the”
Danger area” and the “Caution area” in the
evaluation area diagram shown in Figure 6.
Examples of the difference in collision avoidance
manoeuvring method due to the difference in
parameter setting will be shown below. The situation
when the bow crossing distance was 1.2 miles as a
result of the collision avoidance manoeuvre is shown
in Figure 7. Figure 8 shows the situation of seeing
own ship from the other target ship at the same time.
Figure 9 shows the situation in the evaluation area
diagram shown in the previous section. The bow
crossing distance is 1.2 miles, the bearing changing
rate is sufficient, it is not a situation that gives anxiety
to the target ship.
Figure 7. The situation when the bow crossing distance was
1.2 miles as a result of the collision avoidance manoeuvre
(Manoeuvring using a simulator)
137
Figure 8. The situation of seeing own ship from the other
target ship at the same time.
Bow Crossing
Dist. [Miles]
[Head-on / Crossing Situation]
Danger
Caution
Safety
Figure 9. The evaluation area diagram, Bow crossing
1.2miles
Figure 10 shows a view of the situation at the bow
crossing distance 0.4 miles as a result of collision
avoidance manoeuvring. And Figure 11 shows the
situation of seeing own ship from the other target ship
at the same time. Figure 12 shows the evaluation area
diagram. All plots are evaluations of “Caution area”.
In Figure 11, it is a situation still shows own ship
starboard side to the other target ship at the distance
is 0.4mile. It can be said that it is a situation giving
anxiety though collision can be avoided. In the
automatic collision avoidance system proposed this
paper, the parameters are set so as to avoid collision
without giving anxiety as shown in Figure 10 to
Figure 12. In other words, parameters were set not to
enter the “danger area” or “Caution area” in the
evaluation area diagram.
Figure 10. The situation when the bow crossing distance
was 0.4 miles as a result of the collision avoidance
manoeuvre (Manoeuvring using a simulator)
Figure 11. The situation of seeing own ship from the other
target ship at the same time. (Situation still shows own ship
starboard side to the other target ship at the distance is
0.4mile)
Safety
Caution
Danger
[Head-on / Crossing Situation]
Dist. [Miles]
Bow Crossing
Figure 12. The evaluation area diagram, Bow crossing
0.4miles
5 COMPARISON OF MANOEUVRING RESULTS
BY AUTOMATIC COLLISION AVOIDANCE
SYSTEM AND MANOEUVRING RESULT BY
HUMAN
Verification experiments were carried out using a full
mission simulator manufactured by Japan Marine
Science (JMS). The photograph of the full mission
simulator to be used in this study is shown in Figure
13. The angle of visibility of the full mission simulator
is 360°, and it is capable of reproducibility in the
downward direction as well. In addition, the JMS full
mission simulator uses a high-resolution projector (4
times the resolution of a normal high-definition
television: 4 K).
Figure 13. Full mission simulator used in this study (Japan
Marine Science made)
Experimental scenario in actual congested sea area
is shown in Figure 14. It is a real congestion sea area
in the coast of Japan. In order to head to Osaka bay,
the own ship encounters many crossing vessels and
138
sets <056> as the initial course and then alters her
course to <020>, <003>. It is a difficult scenario to alter
her course while avoiding crossing vessels from her
starboard side and port side. In the experiment,
automatic collision avoidance system is acquiring
data of other vessels from automatic identification
system (AIS).
0 20NM
0 38000m
Head-on Vessels,
Same way Vessels
<056>
<020>
<003>
Own Ship
Planed Route
Figure 14. The scenario in which verification experiments
were carried out (A real congestion sea area in the coast of
Japan)
Figure 15 shows the results ship track chart and
relative track chart of collision avoidance
manoeuvring by the automatic system. Figure 16
shows collision avoidance manoeuvring by veteran
captain. Figure 17 shows collision avoidance
manoeuvring by inexperienced officer. Figure 18
shows the situation of relative distance and bearing
change rate of all encounter vessels in Evaluation area
diagram. Evaluation points (deduction points)
calculated by Equation (5) are shown in Table 1. There
was a deduction only for manoeuvring by an
inexperienced officer. There was no deduction point
in manoeuvring of the automatic system and the
veteran captain.
Track Chart Relative Track Chart
Own Ship
Own Ship
2 1 0 1 Dist. [Miles]
0 2 4 Dist. [Miles]
2 1 0 1 Dist. [Miles]
0 2 4 Dist. [Miles]
Automatic System
Figure 15. The results ship track chart and relative track
chart of collision avoidance manoeuvring by the automatic
system
0 2 4 Di st. [Miles]
2 1 0 1 Dist. [Miles]
Relative Track ChartTrack Chart
Own Ship
Own Ship
2 1 0 1 Dist. [Miles]
0 2 4 Dist. [Miles]
Veteran Captain
Figure 16. The results ship track chart and relative track
chart of collision avoidance manoeuvring by veteran
captain
2 1 0 1 Dist. [Miles]
0 2 4 Di st. [Miles]
Relative Track ChartTrack Chart
2 1 0 1 Dist. [Miles]
0 2 4 Dist. [Miles]
Own Ship
Own Ship
Inexperienced Officer
Figure 17. The results ship track chart and relative track
chart of collision avoidance manoeuvring by inexperienced
officer
Dist. [Miles] Dist. [Miles] Dist. [Miles]
Bow CrossingStern Crossing
Bearing Changing rate [deg./min.]
Danger Danger
DangerCaution
Caution
Caution Caution
Caution
Safety
Safety Safety
Safety
Safety
Safety
The evaluation diagram of the same way was omitted
Automatic System Veteran Captain Inexperienced Officer
[Head-on / Crossing Situation]
[Head-on / Crossing Situation]
[Head-on / Crossing Situation]
Figure 18. The situation of relative distance and bearing
change rate of all encounter vessels in Evaluation area
diagram
Table 1. Evaluation points (Deduction points)
_______________________________________________
Automatic Veteran Inexperienced
System Captain Officer
_______________________________________________
Score -0.0 -0.0 -5.7
_______________________________________________
When comparing the own ship's track chart,
human steering is deviated to the larger than the
manoeuvring by the automatic system in order to
avoid the crossing vessels. The automatic system
constantly calculates the optimum course for all
vessels in the area shown in Figure 3 as well as in the
immediate dangerous vessel. As a result, even if there
were many crossing vessels from the starboard, the
deviation was relatively small. Comparing the
navigation between the automatic system and the
veteran captain, the own ship’s track chart is slightly
different, but neither has a deduction point and it is
judged that it was almost equivalent manoeuvring.
Veteran captain and the automatic system only
139
avoided the two crossing vessels from the starboard
side, but inexperienced officer delayed his judgment
and also avoided the third crossing vessel. As a result,
the deviation became bigger and the evaluation of the
crossing vessels entered the “Caution area” and a
deduction occurred.
6 VERIFICATION EXPERIMENT ON ACTUAL
SHIP
Validation experiments were conducted to verify the
effectiveness of the automatic collision avoidance
system on actual ship navigating congested waters in
Japan's coastal waters. The verification experiment
was conducted for 3 days. The main Particulars and
photographs of "Kouzan Maru" boarded for the
experiment are shown in Figure 19.
Cement carrier
GT:
Deadweight tons:
LOA:
Lpp:
Draft:
Speed:
“Kouzan Maru”
14,902t
22,053t
160.9m
153.7m
8.9m
13.0kt
Figure 19. “Kouzan Maru” boarded for the experiment
In the verification experiment on a real ship, risk
calculation was carried out using mainly AIS
information. At the time of navigating in congested
water area, AIS information reached about 500 ships,
but there was no problem in processing in real time.
Figure 20 shows the view of the on-board experiment
off the coast of Yokohama immediately after leaving
Tokyo. The track chart and relative track chart sailing
off the coast of Yokohama according to the instruction
by the automatic collision avoidance system are
shown in figure 21.
Figure 20. The view of the experiment off the coast of
Yokohama immediately after leaving Tokyo
Relative Track Chart
Track Chart
Own Ship
Own Ship
Crossing Ships
Crossing Ships
Same-way Ship
Same-way Ship
Yokohama
Alter Course to Stb’d 10 deg.
2 1 0 1 Dist. [Miles]
8 6 4 2 0 Dist. [Miles]
2 1 0 1 Dist. [Miles]
6 4 2 0 D is t. [Miles]
Figure 21. The track chart and relative track chart sailing off
the coast of Yokohama (Automatic Manoeuvring)
Preference Course : Stb’d 10 deg
.
Preference order
Risk
Own Ship
Crossing Ships
Same-way Ship
Preference Course
Figure 22. A picture of a situation where the automatic
collision avoidance system instructs to alter her course to
starboard (Sailing off Yokohama)
Ca uti on
Ca uti on
Bow CrossingStern Crossing
Bearing Changing rate [deg./min.]
[H ea d- on / Cro s sin g Situation]
[Same-way Situation]
Dist. [Miles]
Dist. [Miles]
Danger
Ca uti on
Figure 23. The result in the evaluation area diagram
(Distance and bearing change rate), sailing off Yokohama
A picture of a situation where the automatic
collision avoidance system instructs to alter her
course to starboard is shown in Figure 22. It is a
situation where crossing ships from the starboard side
are encountered with the manoeuvring area being
restricted by same-way ships. The instruction of the
automatic collision avoidance system is an altering
course to starboard 10 degrees. The evaluation result
in the evaluation area diagram (Distance and bearing
change rate) in the same area is shown in Figure 23.
140
Figure 24. The view of the experiments in areas with
relatively high congested water around Japan coast
Own Ship
Own Ship
Head-on Ships
Head-on Ships
2 1 0 1 Dist. [Miles]
2 1 0 1 Dist. [Miles]
8 6 4 2 0 Dist. [Miles]
Alter Cour s e to Stb’d 8 deg.
Track Chart
Relative Track Chart
8 6 4 2 0 D ist. [Miles]
Figure 25. The track chart and relative track chart in the
situation of encounter with head-on ships
Own Ship
Risk
Preference order
Preference Course : Stb’d 8 deg.
Head-on Ships
Preference Course
Figure 26. A picture of a situation where the automatic
collision avoidance system instructs to alter her course to
starboard (in the situation of encounter with head-on ships)
Figure 24 shows the view of the experiments in
areas with relatively high congested water around
Japan coast. In the situation of encounter with head-
on ships, the track chart and the relative track chart is
shown in Figure 25. Figure 26 shows a picture of a
situation where the automatic collision avoidance
system instructs to alter her course to starboard to
avoid end on target ships. And the evaluation result
in the evaluation area diagram (Distance and bearing
change rate) is shown in Figure 27. A sufficient
distance and bearing change rate can be secured.
Danger
Caution
Caution
Caution
[Head-on / Crossing Situation] [Same-way Situation]
Bow CrossingStern Crossing
Bearing Changing rate [deg./min.]
Dist. [Miles]
Dist. [Miles]
Figure.27. The result in the evaluation area diagram
(Distance and bearing change rate), in the situation of
encounter with head-on ships
The comments of Master of “Kouzan Maru” are as
follows.
There is no discomfort in the collision avoidance
manoeuvring method instructed by the automatic
system.
Captain himself makes a bigger course change in
order to clearly show the intention of avoiding
own ship to the target ship, compared with the
automatic system. (In case of Figure 26)
A system that graphically displays the status of
risk calculation to the operator is effective as a
navigation assistance device.
7 CONCLUSION
Main findings obtained by this study are described
below.
In order to carry out strategic collision avoidance
manoeuvring, an automatic collision avoidance
system constantly calculating optimal
manoeuvring method was introduced.
A system that evaluates the situation that entered
"Danger area" and "Caution area" using the
relative distance and bearing change rate with a
deduction-based evaluation system was proposed.
It was introduced that the parameters for the
proposed automatic collision avoidance system
were set so as to avoid collision without giving
anxiety to the target other ships.
Validity verification of the developed automatic
collision avoidance system was carried out
compared to the manoeuvring results of veteran
captain and officers.
It was verified that the collision avoidance
manoeuvring by the automatic collision avoidance
system is almost equal to that by veteran captain.
Compared to human steering, the automatic
system constantly calculates the optimum course,
which suggests that there is a tendency for less
deviation from the planned route.
Verification experiments were successfully
conducted to verify the effectiveness of the
proposed automatic collision avoidance system on
the actual ship navigating in congested waters.
It was confirmed that the manoeuvring method
instructed by the automatic collision avoidance
system has no discomfort for Master and officers.
Master of “Kouzan Maru” who joined the
experiment commented that he himself would
141
make a bigger course change in order to clearly
show the intention of avoiding own ship to the
head-on target ship, compared with the automatic
system. This is a future study topic.
It was confirmed that graphically displays the sta-
tus of risk calculation to the operator is effective as
a navigation assistance device.
In this experiment, other ships information was
acquired only by AIS. It is necessary to consider
incorporation of radar information in order to
obtain information on vessels, obstacles etc. not
equipped with AIS. In the next experiment on the
actual ship, authors plan to incorporate radar
information.
ACKNOWLEDGEMENTS
The authors thank Capt. Kuwabara and Chief Officer Ms.
Nishimura of JMS for their cooperation in the simulator
experiment. And also, thanks Capt. N. Saburoumaru /
Master of “Kouzan Maru” and other officers.
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