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1 INTRODUCTION

1.1 Characteristics of DPS and DPclass

As an automatic position-keeping controller, i.e., the

Dynamic Positioning System (hereafter DPS),

maintains vessel’s position by automatically

controlling the power supply, thrusters and other

propulsion equipment [1]. The International Maritime

Organization (IMO) defines three classes of DPS based

on their degree of redundancy: classes A, B and C. In

Japan, the classification society, Nippon Kaiji Kyokai

(Class NK), established three identical classification

codes. DPclass A holds a significant share of the global

DPS market, primarily due to its lower cost and the

minimal design standards required for DP operation

compared to DP classes B and C. In contrast, DP classes

B and C are more expensive but offer greater

redundancy, ensuring that a single system failure does

not result in total system failure. Notably, DP class C

can maintain the vessel’s stability in a serious incident,

such as installation compartment loss due to fire or

flooding [1]. In contrast, DP Class Ahas no

redundancy, meaning a single fault could lead to a loss

of position. Consequently, the reliability of the three

DP classes varies [2].

1.2 DP Vessel Marine Incidents

The percentage of maritime incidents due to inaccurate

positioning of DP vessels has been increasing since

2019 and continues to rise (2015–2023; see Figure 1) [3,

4].

These incidents often entail DPS-equipped vessels

being in incidents due to incorrect positioning

information from the Global Navigation Satellite

System (GNSS) and other sources. Inaccurate

positioning can result in drift-off (vessel position

deviation due to power failures, generator issues or

The Use of Simulators for the Emergency Response

Training of Dynamic Positioning Operators of Class A

Vessels

H. Katakura

, M. Saito

& T. Takemoto

Toba National College of Maritime Technology, Toba, Japan

Marine Technical College, Ashiya, Japan

Tokyo University of Marine Science and Technology, Tokyo, Japan

ABSTRACT: The Dynamic Positioning System is classified into three types: DP class A, B, and C. DP class A

vessels hold an overwhelming market share, but it lacks redundancy and is prone to failures. Therefore, in case

of failure, there is a possibility of loss in positioning. Herein, we postulated that training Dynamic Positioning

Operators (DPOs) for emergencies should mitigate maritime incidents. Accordingly, simulators have been

proposed for achieving this objective. Using an experiential approach, nine DPOs were exposed to DPS simulation

emergency response training at a lab in Japan. Each participant was given four tasks and a checklist to assist in

decision-making to avoid collisions in various scenarios involving marine structures. An analysis of the simulator

experiments and outcomes indicated that the length of experience in ship handling and prior training influenced

DPOs performance. The study concluded that DPOs should take more effective training to maintain proper

positioning for the safe operation of DP vessels.

http://www.transnav.eu

the International Journal

on Marine Navigation

and Safety of Sea Transportation

Volume 19

Number 3

September 2025

DOI: 10.12716/1001.19.03.08

760

power supply failures), drive-off (deviation from the

target position due to inaccurate GNSS data) and force-

off (deviation caused by external forces), among others

[5].

Figure 1. Percentage of marine incidents due to incorrect

location of DP vessels (2015～2023)

Marine incidents on DP vessels are attributed to

several factors, as illustrated in Figure 2 [6]. Thruster

(propulsion system) and computer (information

processing system) failures account for over half the

marine incidents on DP vessels. Other contributing

factors include power (output system), the position

reference system, humans (human element) and the

environment (environmental element).

Figure 2. Causes of marine incidents on DP vessels (2023, n =

1230)

1.3 Significance of Human Resource Development on DP

Operations

Previous research has shown that operators must

possess appropriate seafarers skills to operate ships

safely and handle all potential situations efficiently [5,

7].

Accumulating sufficient experience to develop a

sense of ship handling through actual ship experience

is a complex task for operators [8]. Hence, ship-

handling simulators are an effective means of

supplementing experiential learning for inexperienced

operators [9].

Training to improve emergency ship handling skills

is also considered necessary to hone skills [5],

including responding to rare accidents on board, such

as emergency responses following an accident [2, 5] or

escaping from a crisis to avert a near accident [9].

The Certification and Accreditation Standards,

Volume 1 - Training and Certification, published by the

Nautical Institute (hereafter NI), an international

professional body for maritime professionals,

identifies Dynamic Positioning Operators (hereafter

DPOs) as pivotal to meeting safety standards. These

operators must possess the confidence, competence

and experience to respond appropriately to major DPS

failures. The DP Emergency Ship Handling Course is

designed to equip malfunctions [10].

1.4 Purpose of this Study

A review of previous studies has highlighted the

increase in maritime incidents attributed to the

incorrect positioning of DP vessels [4,5,8]. Several

factors have contributed to these accidents [5, 8]. Until

May 2022, domestic DP simulator training was not

conducted in Japan, leaving young DPOs without the

necessary training in crisis prevention maneuvering

techniques. The inability of inexperienced DPOs to

develop these essential skills highlighted a significant

training gap, particularly in Japan’s maritime

environment [11]. Given these realities, this study aims

to identify how changes in position information affect

emergency DP operations conducted by DPOs. The

study explores which DP operation features help

mitigate the risk of collisions and examines measures

to enhance DPO skills in emergencies. A simulator

experiment was conducted with DPOs to assess their

ability to avoid collisions with offshore structures

under diverse conditions to achieve this objective. A

results analysis yielded fundamental insights for the

development of training methods. Ultimately, the aim

is to gather pivotal data as input for improving training

and the current DPS training scenario needs to

consider that the content of a given task is of

cumulative importance to training and experience.

2 EXPERIMENTAL METHOD

2.1 Devices used in the experiment

2.1.1 DPS Simulator

The DPS used in the experiment was manufactured

in Japan and the same system was installed on

oceanographic research vessels and other types of

ships. These DP vessels are equipped with bow

thrusters and two stance thrusters (No. 1 and No. 2), a

controllable pitch propeller (CPP), a rudder and two

GNSSs: GNSS No. 1 (primary) and No. 2 (secondary).

Additionally, the vessels have two main generators

and one shaft generator. Three video cameras were

positioned to capture the experimental footage: one

behind the ship handling simulator, one in front of the

participant’s ship handling table and one behind each

participant in the study. Participants were also

equipped with an eye-tracking device to monitor their

gaze.

2.1.2 Monitoring function

The DPS simulator is illustrated in Figure 3. It

consists of an instructor’s console on the left and a

participant’s console on the right. During the

experiment, authors used a timer to record the

measured time, distance from the offshore structure to

the DP vessel, and speed and position while

monitoring the display at the instructor’s table.

Meanwhile, the participant performed DP operations,

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observing the four monitors (Figure.4-6) positioned in

front of the console.

Figure 3. DPS Simulator

The details of forwards screen 1 and 2 are illustrated

in Figure 4. Screen 1 illustrates the DP vessel’s track

chart, which can be viewed on the same view as the

instructor’s console. Screen 2 is displayed in Figure 4,

comprising a main screen on the left and a sub screen

on the right. The main screen allows selection from one

of the eight items, while the sub screen offers four

options from 19 items.

Figure 4. Screen 1(Left figure) & Screen 2 (Right figure)

2.1.3 Alarm Device & Remote Control Box

The DPS simulator’s forwards screen 3, illustrated

in Figure 3, alerts the user to the alarms, of which there

are two types: system and operational. System alarms

indicate equipment malfunctions and other issues

related to the DPS. In contrast, operational alarms

provide information pertinent to DP operations, such

as deviations between the actual heading and set

heading.

Figure 5 illustrates forwards screen 4, which can be

correlated with forwards screen 1, as it displays the DP

vessel’s track chart. Additionally, forwards screens 4

and 2 are identical.

Figure 5 illustrates the remote control box used in

the experiment, featuring a turn dial, a joystick and a

button for switching between the DP operation modes,

as illustrated in Figure 5.

Figure 5. Forwards screen 4 (participant’s console screen)

& Remote Control Box

2.2 Participants

The participants’ profiles are indicated in Table 1. Nine

DPOs participate in the experiment: four from a marine

survey company and five from a marine engineering

company. Their ages ranged from 27 to 45 years, with

a mean age of 32 ± 5.8 years. The years of experience

operating a DPS at sea ranged from 0.7 to 9.0 years,

with a mean experience of 3.0 ± 2.4 years. In Japan,

seafarers must meet specific experience requirements

to operate a DPS [1]. Table 1 illustrates that all

participants met the DP class A operating experience.

Table 2 presents the participants’ training and ship

handling history. Five participants completed the DPS

training provided by the manufacturer, while another

five had experience in emergency response.

Additionally, eight participants had experience DP

operation by a single.

Table 1. Participant profiles

DPOs

Age

Years of experience

(Boarding)

Years of experience

(DP operation)

DPS

class

Rank

2 years 5 months

1 year 11 months

3/O

1 year 4 months

1 year 1 month

3/O

–

2 years

A, B

2/O

–

9 years

A, B

1/O

–

1 year 6 months

2/O

–

3 years

A, B

Capt

–

3 years

2/O

10 months

8 months

3/O

1 year 5 months

1 year 2 months

2/O

Table 2. Participant’s training & ship handling history

Participants

NI Training

(end of the day)

Experience in emergency

response

Single DP

operation

〇

Control screen freeze, GPS

signal disruption, etc.

〇

Basic

(2020.2.21)

〇

Advance

(2014.1.10)

Thruster & generator stop,

etc.

〇

Basic

(2021.2.17)

〇

Basic

(2019.3.15)

Uncontrollable main

azimuth thruster etc.

Advance

(2022.9.2)

Out of position, suspend

the use of stern thrusters,

etc.

〇

GPS anomalies

〇

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2.3 Criteria and Setup contents of the experimental task

2.3.1 Setting criteria and items

The criteria for establishing the experimental tasks

were based on the emergency response plans and

procedures outlined in the class NK guidelines [12].

The number of domestic offshore structure

construction is less common than its European

counterpart. Factors such as domestic weather

conditions, work stoppage criteria and unique

regulations (e.g. the Ship Safety law) complicate

directly applying European standards. Therefore, by

setting the experimental task criteria to align with the

characteristics of domestic marine structure, the

authors believe that they can contribute to preventing

incidents in advance. The emergency response plan

should include the following, as necessary: (a)

emergency arrangements (communication network),

(b) adverse weather conditions (including strong

winds, lightning, etc.), (c) earthquake or tsunami,

(d)pre- determined limits of structural parameters,

(e)predetermined limits of resilience (or stability)

parameters, (f)DPS-related matters, (g) structural or

equipment damage, (h)mechanical, electrical or control

system failure, (i) fire, (j)collision, grounding, (k)

leakage, flooding and (l) personal injury [12]. The

experimental setup was designed to prepare for these

scenarios, assuming the operational tasks of a DP

vessel necessary for emergency response. All

participants consecutively performed Tasks 1–4 to

assess their emergency response and operational skills

in handling a near-accident crisis. Domestic marine

structure has anti-collision measures in sea area and

Marine Warranty Survey agree- d [12]. The four tasks

are illustrated in Figures 6–9.

2.3.2 Task 1

Task 1 is illustrated in Figure 6. The DP vessel

begins 150 (m) from the offshore structure, indicated

by the red circle at the top of the diagram. As the DP

vessel departs, it approaches the offshore structure

without equipment failure. However, one stern

thruster fails after the vessel has travelled 50 (m) (noted

by the orange circle). Consequently, the vessel has only

the bow thrusters and one functioning stern thruster.

DP vessels must avoid collisions with the offshore

structure, maintain a minimum distance of 100 (m)

from the departure point and stop at least 50 (m) away

laterally from the offshore structure. The end point is

marked by the red circle in the diagram in Figure 6.

Figure 6. Task 1 (Left figure: Start position of the DP vessel;

Right figure: Stop position)

2.3.3 Task 2

Task 2 is illustrated in Figure 7. Once the DP vessel

reached a position 50 (m) lateral from the offshore

structure, the stern thruster was activated, allowing the

vessel to commence Task 2 while positioned east of the

structure. During the experiment, DP vessels

maintaining a fixed point were exposed to steady

(northeast direction, less than 10 (m/s)) and gusty wind

(northeast direction, 10 (m/s)). Each measurement

period lasted 5 (min). The DP vessels must move away

if they are close to prevent collisions with offshore

structures. They are also expected to maintain a fixed

position for approximately 10 (min). The DPO must

also contact the individual in charge of the offshore

structure if the vessel departs from its vicinity.

Figure 7. Task 2 (DP vessel with gusty wind)

2.3.4 Task 3

Task 3 is illustrated in Figure 8. After the DP vessel

maintained a fixed position, a failure occurred in its

GNSS (No. 1/No. 2) when it was 100 (m) away from the

offshore structure. This failure led to inaccurate

positioning information for the DP vessel. The DPO

attempts to hold a fixed position but must also execute

an emergency breakaway to prevent colliding with the

offshore structure; thus, the DPO directs the vessel to

move to a position 100 (m) away. Following the DPO’s

emergency departure, the DP vessel was moved to the

designated distance, but the GNSS (No.1/No. 2)

subsequently malfunctioned.

Figure 8. Task 3 (Left figure: emergency leave; Right figure:

start position)

2.3.5 Task 4

Task 4 is illustrated in Figure 9. Once the GNSS

position information was confirmed as accurate, the

experiment began in an environment free of equipment

malfunctions involving the DP vessel and external

forces. On short notice, the individual in charge of the

offshore structure contacted the DPO regarding

transferring an injured person and instructed him to

approach the offshore structure. Measurements were

collected from the point where the DP vessel received

these instructions. The DPO manoeuvred the DP vessel

to turn around and approach the offshore structure.

The DP vessel had to stop, rotate its bow heading to the

south and maintain a lateral distance of 50 (m) from the

offshore structure to avoid a collision.

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Figure 9. Task 4 (Left figure: pivot-turn manoeuvring; Right

figure: final position of the DP vessel)

2.4 Experimental procedure

After explaining the experiment, the participants

engaged in the DP operation for approximately one

hour to familiarize the system. The experiment was

conducted between 13:00 and 17:00 to account for the

influence of circadian rhythms on the data. The

participants performed DP operations while seated at

their consoles, viewing the four monitor screens in

front of them. While the participants operated the DP

system at their consoles, the authors assumed the roles

of captain, chief engineer and person in charge of the

offshore structure at the instructor’s console. When

necessary, the participants communicated via a

transceiver with the captain, chief engineer or person

in charge of the offshore structure.

The participants manoeuvred the vessels using four

DP operation modes: STANDBY (standby), JOYSTICK

(manual), AUTO HEAD (semiautomatic operation,

where only the bow is automated and the DP operation

is conducted via JOYSTICK) and AUTO DP (fully

automatic operation).

2.5 Preliminary Experiment

A preliminary experiment was conducted with

students from a seafarers’ training institute to develop

research items focused on collision avoidance decision-

making for DP vessels [13]. The DPS simulator was

verified to be functional before the experiment. Figure

10 illustrates the preliminary experiment.

Figure 10. Preliminary experiment

The collision avoidance decision-making research

items listed in Table 3 were established using the

results of the preliminary experiments. Ten items were

examined for collision avoidance decision-making for

each task. During the preliminary experiments, the

order of the research items for collision avoidance

decision-making varied across tasks. The following

section details the items investigated for collision

avoidance decision-making.

Table 3. Collision avoidance decision-making research items

Task

Setting the DP point

Alarm confirmation

Range adjustment

Switching the sub screen

Generator check

Radio communication

Switching the operation

mode

Speed

Switching the main screen

Sensor check

Task

Switching the operation

mode

Heading

Setting the DP point

Use of capability plot

Switching the sub screen

Radio communication

Range adjustment

Emergency avoidance

Speed

Switching the main screen

Task

Alarm monitoring

Switching the operation

mode

Switching the main screen

Setting the DP point

Radio communication

Sea transfer

Switching the sub screen

Sensor check

Speed

Range adjustment

Task

Setting the DP point

Speed Heading

Setting of the DP Circle

Radio communication

Alarm monitoring

Switching the operation

mode

Switching the sub screen

Gain adjustment

Range adjustment

The DP point and DP reference point are illustrated

in Figure 11. The DP point, represented by a square

mark, is designated by the DPO to maintain the DP

vessel at a fixed location and is identified as the DP

reference point (illustrated as a blue circle). The DP

reference point is where the DPO must ensure the DP

vessel remains. The DPO can adjust the DP point and

DP reference point settings. The DP point operation

screen, highlighted in the red frame in Figure 11, is

organized into categories: latitude and longitude,

bearing and distance, north, south, east and west and

UTM coordinates (Universal Transverse Mercator,

projecting the Earth’s coordinates onto a planar view).

The DP point can be modified by entering the desired

coordinates on the screen on the red frame.

Changes to the DP reference points are illustrated in

Figure 12, with the operation screen on the left and the

coordinate system on the right. The operation screen is

organized into five categories from top to bottom:

Reference Point (hull reference point), BT Winch

(winch), CTD (Conductivity Temperature Depth:

oceanographic instrument), A-frame and Key-in

(numerical input). The coordinate system is presented

on the right side of Figure 12, specifying the x- (m) and

y-coordinates (m) for each item on the operation

screen. Consequently, the DPO can select from these

five items. Once the DPO has input the changes for the

DP point, the adjustments on the confirmation screen

(latitude and longitude) for the DP point operation can

be reviewed, as illustrated in Figure 13 (Left figure).

After entering the DP reference point change, the DPO

updates the DP reference point on the operation check

screen, as illustrated in Figure 13 (Right figure).

Figure 11. DP point & DP reference point (Left figure) &

Operation screen of the DP point (Right figure)

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Figure 12. Change of DP reference point

Figure 13. Operation check screen (Left figure: DP point;

Right figure: DP reference point)

‘Radio communication’ refers to the DPO’s use of a

transceiver to contact the captain, chief engineer or

person in charge of the offshore structure. ‘Alarm

confirmation’ denotes the DPO’s verification of the

system and operational alarms within the DPS. ‘Range

adjustment’ involves the DPO altering the scale of the

DPS screen by using the top left slide bar, as illustrated

in Figure 14. Speed refers to the DPO’s adjustment of

the DP vessel’s movement in the vector direction. The

setting of the speed is illustrated in Figure 14. When the

vessel operates in the AUTO DP mode, the DPO can

adjust the vessel’s speed by inputting the desired speed

into the screen highlighted in the red box in Figure 14.

Figure 14. Range setting (Left figure) & Setting of the speed

(Right figure)

The main screen and the sub screens are displayed

in Figure 15. ‘Switching the main screen’ refers to the

DPO’s implementing a single main screen change. The

DPO switches sub screens by selecting four out of the

available 19 sub screens and implementing the

necessary changes to these four.

Figure 15. Main screen (Green frame) & Sub screens

The ‘generator check’ requires the DPO to verify the

output values of the two main generators and one shaft

generator.

The ‘sensor check’ requires that the DPO ensures

the position sensor and GNSS (No.1/No.2) are

functioning correctly.

The ‘heading’ indicates the change in the bow

heading of the DP vessel as managed by the DPO.

‘Emergency avoidance’ refers to DPO utilizing the

operational mode for an emergency evacuation.

Figure 16 illustrates the capability plot. This

theoretical simulation graph corrects for noise in the

observed values. It provides an estimate based on

weather, sea conditions and the DP vessel’s capabilities

(e.g. number of thrusters) [14, 15].

Theoretical simulation graphs identify new

propulsion systems and sudden disturbances, estimate

bow heading and determine position deviations. DPOs

use capability plots to understand the limitations of

these indications DPOs should not place excessive trust

in the estimates provided by capability plots, however,

as they do not accurately reflect the actual field

environment.

Figure 16. Capability plot

‘Alarm monitoring’ is the DPO’s response to the

DPS information regarding the system and operational

alarms. For instance, if an ‘Out of Red Circle’ alarm

occurs (indicating that the position is outside the red

circle), the DPO corrects the issue by repositioning the

vessel within the red circle.

A ‘sea transfer’ occurs when a DPO moves a DP

vessel from one position to another.

The DP circle is illustrated in Figure 17. The centre

of the DP circle represents the DP point, while the

‘Setting of the DP circle’ involves the DPO establishing

three concentric circles. These circles are defined by the

allowable radii of the red, yellow and green circles. The

green circle is the closest to the DP vessel, the yellow

circle is the second closest, whereas the red circle is the

furthest away. The DPO manoeuvres the DP vessel to

ensure it remains within these designated circles.

Figure 17. DP circle (alarm circle)

Figure 18 illustrates the gain setting screen. The

gain adjustment process requires the DPO to modify

the dimensional and PD gains. Dimensional gains

control the movement of the DP vessel in the

forwards/backwards, left/right and turning directions.

In contrast, the PD gains refer to the proportional (P)

and derivative (D) gains for these same directions.

These two gains apply only to semiautomatic and fully

automatic operation modes. ‘Switching the operation

modes’ entails the DPO changing among the four

operational modes of the DPS. Figure 18 illustrates the

screen displaying the GNSS (No.1/No.2) malfunction

in the STANDBY mode. This screen is characterized by

the position information (e.g. latitude, longitude)

changing to red and accompanied by activating an

alarm.

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Figure 18. Gain setting screen (Left figure) & The screen of

GNSS (No.1/No.2) malfunction (Right figure)

3 RESULTS

3.1 Experiment (Task 1)

Table 4 indicates the experimental results categorized

by research items and participants. Results in Table 4

are marked with a 〇 if all participants completed 10

of the research items based on the information

obtained from the four forwards monitor screens;

conversely, they are marked with a ● if they were

unable to do so. All participants performed the

research items without issues, except for the ‘speed’

item. The speed varied from 0.1 (kt) to 0.7 (kt) for all

participants who had attended the training and

maintained a low ‘speed’.

Table 4. Experimental results by Research items (Task 1)

Under the ‘speed’ section, the set speed (kt) for

those operating with the AUTO DP and set speed with

the JOYSTICK is illustrated in Figure 19. The set speed

of AUTO HEAD can be used in the JOYSTICK. The use

of AUTO DP was five participants and the change in

speed (kt) with the AUTO DP is illustrated in Figure

20. Participants C, E and G, each with three years or

less of sea experience while operating with the AUTO

DP, had set vessel speeds of less than 0.5 (kt).

Participants C, E, G and H, each with three years or less

of experience at sea, operated the DP vessel at a

maximum speed of 1.6 (kt) or less, bringing it close to

the offshore structure.

Figure 19. Set speed with the AUTO DP (Left figure) & Set

speed with the JOYSTICK (Right figure)

Figure 20. Change in speed operated with the AUTO DP

The change in speed (kt) with the AUTO HEAD is

presented in Figure 21. Of the four participants while

operating with the AUTO HEAD, Participant D, with

nine years of experience at sea, operated the vessel at a

maximum speed of less than 0.5 (kt). In contrast,

Participants A, B and I, all with less than nine years of

experience, exhibited a significant change in speed.

With his nine years of experience and operating under

the AUTO HEAD, Participant D showed a minimal

speed change (kt). The results in Figure 19 (Right

figure), 21 validate Participant D’s AUTO HEAD

(JOYSTICK) operation, who has extensive in-service

experience. Participant D, while using the AUTO

HEAD, successfully approached the DP reference

point and halted the vessel by gradually reducing

speed, setting the JOYSTICK to neutral in small

increments, within 40% or less of the JOYSTICK output

value (left/right direction).

Figure 21. Change in speed operated with the AUTO HEAD

Figure 22 illustrates the deviation between the DP

point and DP reference point for Participants C, E, F, G

and H, all of whom had three years or less of in-service

experience and operated in the AUTO DP mode. In

these cases, the DP reference point position served as

the hull reference point, meaning that the distance

represented in Figure 22 corresponds to the distance

travelled by the hull reference point. As these

Participants adjusted the DP point’s position, the DP

point’s distance reflected the distance travelled by that

point.

Participants F and H, both with three years or less

of sea experience and operating in the AUTO DP, set

their DP points further from the DP reference point.

This led to significant speeds towards the DP reference

point due to the large deviation between the two.

Furthermore, Participants C and F incorrectly entered

the DP point settings within the first five minutes of the

experiment. It was also noted that Participant G

adjusted the DP point setting more than ten times,

resulting in an extended DP operation time.

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Figure 22. Deviation of the DP point & DP reference point

maneuvered with the AUTO DP

Figure 23 illustrates the DP reference point for

vessels operating in the AUTO HEAD mode is

illustrated. For Participants A, B, D and I, who also

operated in the AUTO HEAD, the distance to the DP

reference point corresponds to the distance travelled

by the hull reference point, as the DP and hull reference

points are aligned. While Participants A, B, D and I

stopped their DP vessels approximately 100 (m) from

their intended stopping point, there was some

variation in this distance.

Figure 23. DP reference point manoeuvered with AUTO

HEAD

3.2 Experiment (Task 2)

Table 5 presents the experimental results for Task 2,

organized by research item and participant. In this

table, the results are marked with a 〇 if all

participants successfully performed 10 research items

based on the information obtained from the four

forwards monitor screens; conversely, the results were

marked with a ● if they were unable to do so. Eight

participants, excluding Participant G, did not utilize

the ‘use of capability plot’. Additionally, Participants

F and H could not complete four and six items,

respectively, aside from the ‘use of capability plot’,

while both failed to avoid the emergency. The time to

switch modes illustrated in Figure 24. It was found that

the time taken to switch the modes was less than 4

minutes from the occurrence of the external force until

the collision with the marine structure. The research

item in Task 2, ‘Setting the DP points’, was examined.

Figure 24 illustrates the distance (in metres) from the

DP vessels to the offshore structures. As illustrated in

Figure 24, Participants A–I represent the nine DPOs

operating the vessel in the AUTO DP.

Table 5. Experimental results by Research items (Task 2)

They maintained a fixed position from the DP

vessel to the offshore structure, typically at a distance

of approximately 50 (m), although individual

differences were noted. The DP vessel maintained a

clearance of approximately 30 (m) or more.

Figure 24. Time to switch modes (Left figure) & Distance

from the DP vessel to the offshore structure (Right figure)

Figure 25 illustrates the deviation (m) between the

DP point and DP reference point (defined as wind

speed less than 10 (m/s)) as set by all participants. Each

participant adjusted the DP reference point positions to

align with the hull reference and DP points. The centre

point (x: 0 (m), y: 0 (m)) in Figure 25 represents where

the DP point and DP reference points overlap. The

coordinate values (x (m), y (m)) indicate a smaller

deviation (m) between the DP point and DP reference

point, due to the steady wind conditions affecting the

DP vessel. The results in Figure 25 suggest that all

participants operated the vessel while actively

changing the DP point and DP reference points, as

evidenced by their lack of overlap. The deviation

between the DP point and DP reference point was

smaller for Participants F and G, who each had three

years of experience at sea, compared to Participants A,

B, C, E, H and I, all with less than three years of

experience.

Figure 25. Deviation between the DP point and DP reference

point (Experience at sea: red 9 years; green 3years; orange less

than 3years)

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The deviation between the DP point and the DP

reference point (wind speed: 10 (m/s)) established by

all participants is illustrated in Figure 26. The centre (x:

0 (m), y: 0 (m)) indicates where the DP point and DP

reference point overlap. The coordinate values (x (m),

y (m)) displayed a greater deviation between the DP

point and DP reference point compared to those in

Figure 25, because the DP vessel was affected by wind

gusts. Participant D, who has 9 years of experience at

sea, had a smaller deviation between the DP point and

DP reference point. In contrast, Participants F and G,

each with 3 years of experience at sea, demonstrated

significant deviations, as did Participants A, B, C, E, H

and I, with less than 3 years of experience at sea. Figure

27 illustrates the heading of the DP vessel at wind

speeds of 10 (m/s). Participants D, E, F, H and I, who

had less experience at sea, did not orient the bow of the

DP vessel towards the windward side (northeast). This

oversight resulted in a greater deviation (in metres)

between the DP point and DP reference point.

Figure 26. Deviation between DP point and DP reference(m)

point (Experience at sea: red 9 years; green 3years; orange less

than 3years)

Figure 27.Heading of the DP vessel (wind speed: 10(m/s))

3.3 Experiment (Task 3)

Table 6 displays the experimental results for Task 3,

organized by research items and participants. A 〇

mark indicates that all participants successfully

completed 10 of the research items using the

information from the four forwards monitor screens; in

contrast, a ● denotes they were unable to do so.

Although all participants met the target for each item,

there was variation in ‘speed’, ranging from 0.9 (kt) to

1.7 (kt).

Table 6. Experimental results by Research items (Task 3)

Figure 28 illustrates a scatterplot displaying the DP

reference points for all participants during the ‘sea

transfer’. This scatter- plot also represents the hull

reference point’s position (coordinates (x(m), y(m))), as

all participants used the DP reference point as their

hull reference point. The centre of Figure 28, marked

by the coordinates (x(m), y(m)), indicates where the

GNSS ( No.1/No.2) fault occurred. All participants

were observed to have moved the DP vessel in various

directions, switched to the STANDBY mode from the

four operational modes and maintained their position

near the DP vessel. Participants A, B, C, E, F, G, H and

I, who each had three years or less of in-service

experience, demonstrated a wider range of hull

reference point positions, with the DP vessel remaining

close to the centre of Figure 28. In contrast, Participant

D, with nine years of in-service experience, had the hull

reference point positioned approximately 20 (m)

southeast of the centre of Figure 28, where the DP

vessel was waiting in safe waters.

Figure 28. Scatter plot of the DP reference point (m)

(Experience at sea: red 9 years; green 3years; orange less than

3years)

3.4 Experiment (Task 4)

Table 7 presents the experimental results for Task 4,

organized by research items and participant. The

results are marked as 〇 if all participants could

perform 10 of the research items based on information

obtained from the four forwards monitor screens;

conversely, ● indicated that they could not do so.

While all participants met the target for all items,

there was variation in ‘speed’, ranging from 0.2 (kt) to

1.2 (kt). The research item ‘speed’ in Task 4 was

examined, with the set speed (kt) while operating in the

AUTO DP illustrated in Figure 29. It was observed that

Participant D, with 9 years of experience at sea and

Participants C, E and G, each with less than 9 years of

experience, all set the speed to less than 0.5 (kt) as the

four participants operating the vessel in the AUTO DP.

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Table 7. Experimental results by Research items (Task 4)

The change in speed (kt) when using the AUTO DP

is illustrated in Figure 29. The use of AUTO DP was

four participants and Participants C, E and G, each

with less than 9 years of in-service experience, adjusted

their maximum speed to approximately 1 (kt), enabling

them to bring the DP vessel close to the offshore

structure. In contrast, Participant D, with 9 years of in-

service experience, manoeuvred the DP vessel close to

the offshore structure with speed below 1 (kt).

Figure 29. Change in speed operated with the AUTO DP

Figure 30 illustrates the change in speed (kt) while

operating in the AUTO HEAD mode. Among the five

participants who manoeuvred the vessel, Participant

H, with less than one year of experience at sea,

exhibited a greater change in speed.

Figure 30. Change of speed manoeuvred with AUTO HEAD

The research item in Task 4, ‘Setting the DP Point’,

was verified. The DP point and DP reference point,

both operated with the AUTO DP, are illustrated in

Figure 31. For Participants C, D, E and G, who operated

the DP vessel, the distance of the DP reference point in

Figure 31 is based on the hull reference point, which

was used to set the DP reference point’s position.

Participants C, D, E and G adjusted the DP point’s

position; thus, the distance of the DP point in Figure 31

reflects the distance transferred by the DP point itself.

Participant C, who has two years of experience

operating a vessel with AUTO DP, observed that

setting the DP point further from the DP reference

point result- ed in a greater speed towards the DP

reference point because of the increased deviation

between the two points. Of all the participants (A, B, C,

D, E, F, G, H and I), only those who reached the final

point successfully completed the experiment.

Figure 31. Deviation of the DP point & DP reference point

manoeuvred with the AUTO DP

Figure 32 illustrates the DP reference point for the

vessel operating in the AUTO HEAD mode. The

distance indicated represents the distance travelled by

the hull reference point. Participants A, B, F, H and I

also operated with the AUTO HEAD and used the DP

reference point’s position as their hull reference point.

Of these five participants, H, who had less than one

year of experience at sea, moved the DP vessel a greater

distance to reach the final location.

Figure 32. DP reference point manoeuvered with AUTO

HEAD

3.5 Status of achievement of task goals

Table 8 presents the results of the task goal

achievement by the participants. The results are

marked as 〇 if all participants successfully

completed 11 of the research items based on the

information obtained from the four forwards

monitoring screens and as × if they did not. In Task 1,

the items listed are ‘Do not collide with offshore

structure’, ‘Travel 100 (m) from the start point’, and

‘Stop at a position 50 (m) laterally away from the

offshore structure’.

Task 2 includes the following items: ‘Do not collide

with offshore structures’, ‘If in proximity to an offshore

structure, leave the offshore structure’, ‘The time for

DP vessels to hold a fixed point is approximately 10

minutes’, and ‘If leaving an offshore structure, contact

769

the person responsible for the offshore structure’. Item

of Task 3 is ‘Move to a position 100 (m) away from the

offshore structure’. The items for Task 4 are ‘Stop to

avoid collision with offshore structure’, ‘Heading is

south’, and ‘Stop at a lateral distance of 50 (m) away

from the offshore structure’. While all participants

achieved the targets for all items in all tasks except Task

2, two participants failed to complete the item ‘Do not

collide with offshore structures’, and five participants

did not meet the requirement for ‘Approximate time to

hold the DP vessel at a fixed point for approximately

10 minutes’ in Task 2. The failure in Task 2 for the item

‘Do not collide with offshore structures’ occurred

because the joystick was not tilted forwards and right

oblique (forwards and backwards: + (positive) %, left

and right: + (positive) %) during the emergency

avoidance operation, while Participant F tilted it

backwards (forwards and backwards: - (negative) %,

left and right: 0%) and backwards right oblique

(forwards and backwards: - (negative) %, left/right: +

(positive) %). Participant H tilted the joystick

backwards and rightwards diagonally

(forwards/backwards: - (negative) %, left/right: +

(positive) %). It suggests that improper DP operation

occurred due to the delayed switch modes and the

shorter duration of JOYSTICK compared to AUTO DP.

The five participants who failed to achieve the target of

‘Approximate time to hold the DP vessel at a fixed

point for approximately 10 minutes’ did so because the

bow of the DP vessel was directed northwest, causing

a significant deviation between the DP point and DP

reference point.

Table 8. Outcomes of task goal attainment by participants

4 DISCUSSION

4.1 Discussion of the experimental results for Task 1

For Participants F and H, a greater deviation occurred

when the DP point was separated from the DP

reference point, increasing the vessel speed. Therefore,

it is crucial to be able to ‘Setting the DP point’ and DP

operation training is essential in emergencies. In the

event of a failure of one stern thruster on a DP vessel,

the vessel must respond effectively to the command to

‘Setting the DP point’. Regarding the ability to ‘Setting

the DP point’, all participants met the target; however,

Participant F had no prior experience with single DP

operations, while Participant H had never received

training and lacked experience in emergency response

situations. In terms of ‘speed’, participants with prior

training were able to maintain a low speed.

4.2 Discussion of the experimental results for Task 2

Participant G is the only individual who cleared the

‘use of capability plot’. He had attended advanced

training and had experience in emergency response.

Conversely, among the two participants with multiple

failures in areas other than the ‘use of capability plot’,

Participant F had no history of operating a single DP

operation. At the same time, Participant H had neither

attended training nor had experience in emergency

response. DPOs with less experience at sea displayed a

significant deviation (m) between the DP point and DP

reference point for external forces, particularly with

wind speeds of 10 (m/s). When sudden external forces

occur, it is crucial to manage the ‘Setting the DP point

effectively’. The timely implementation of ‘Setting the

DP point’ by DPOs can help maintain clearance.

Additionally, the DPO adjusts the ‘Setting the DP

point’ to prevent collisions with offshore structures.

4.3 Discussion of the experimental results for Task 3

In the event of a GNSS (No.1/No.2) failure, the DP

vessel must be manoeuvred in all directions from the

point of failure. Therefore, ’Sea transfer’ is crucial for

DPOs with limited in-service experience. Participants

A and I achieved speeds of 1.5 (kt) or more, despite not

previously attending any training. Interconnections

between two tasks is possible to highlight how the

‘Setting the DP point’ in task 1 related to performance

in task 3. This demonstrates the cumulative importance

of training and experience in emergency situations.

4.4 Discussion of the experimental results for Task 4

Participant C believed that ‘Setting the DP point’ was

crucial because deviating more significantly from the

DP reference point allowed for increasing the vessel

speed. Additionally, if there is a change in instructions

from the person responsible for the offshore structure,

addressing the ‘Setting the DP point’ can ensure

sufficient time to implement DP operations.

Participants D and G, who had attended advanced

training and possessed experience in emergency

response, were able to meet the speed target.

4.5 Discussion on the achievement status of the task goal

Participant F, despite having experience in emergency

response and holding the higher rank of captain, failed

two items: ‘Do not collide with offshore structure’ and

‘Approx. 10 minutes as a guide time for holding a fixed

point on a DP vessel’. His performance may have been

affected because less than four years had passed since

he attended training, and he had no experience

770

operating a vessel alone—the only one to do so of the

nine participants. Participant H, who also failed two

items, had no previous training or emergency response

experience and had only eight months of DP operation

experience.

Participant D, a first officer, possessed nine years of

experience in DP operations and emergency response

experience, the longest in DP operations. Despite

performing well in many of the research items, he

failed to meet the requirement for the ‘Approximate

time to hold a DP vessel at a fixed point for

approximately 10 minutes’. Additionally, it had been

eight years and ten months since he completed the

advanced training course. Of the other two participants

who failed this item, Participant E had no experience in

emergency response, while Participant I had never

attended training.

4.6 Limitations of the Study

The study had some limitations, such as the simulator

used in the experiment. Since this was manufactured in

Japan, observing whether equipment manufactured in

other territories produced similar results would be

interesting.

5 CONCLUSION

The demand for maritime vessels with more flexibility

and power requires that DP operations keep abreast of

developments (16)and that the DPO’s response to

emergencies is aligned with these developments. The

following conclusions can be drawn from the

preceding discussion. First, factors such as attendance

at training sessions, the time elapsed since completing

training, years of DP operation experience and

experience in emergency responses are perceived to

influence participants’ performance. For instance,

Participant D’s performance demonstrated that issues

may occur in avoiding collision crises when

experienced DPOs have not retrained for several years

and lack adequate training in emergency response

relevant to real marine scenarios. In response to this

situation, the authors propose the following

recommendations:

1. The training content established by the training

center must be implemented for DP vessels to

mitigate DPO human errors in conducting in

adequate DP operations.

2. Retraining after a lapse of more than nine years

should be mandatory for all DPOs.

3. (3) The simulator training content necessary for

emergency response regarding ‘setting the DP

points’ and ‘sea transfer’ must be revised. These

contents were not included in the training content

provided by the training center.

4. In simulator training for emergency response, the

following objectives should be established:

− In the event of a stern thruster failure on a DP

vessel, the

− ‘Setting the DP point’ must adjusted

accordingly.

− In the event of external forces (wind speed: 10

(m/s)), the

− ‘Setting the DP point’ must be adjusted

accordingly.

− If a GNSS (No. 1/No. 2) fails, the DP vessel

should be moved to safer waters.

− If there is a change in the instructions from the

person responsible for the offshore structure, the

‘Setting the DP point’ should be adjusted

accordingly.

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