277

1 INTRODUCTION

Modern-day navigation has been strongly influenced

by the technology revolution, particularly by

implementing ECDIS in 2018. Navigational bridges

are becoming abundant with automated systems with

a humane machine interface. In such an environment,

a navigator's attention is easily moving from the

bridge window and real surroundings to the

electronic presentation of information obtained by

numerous sensors. Such deprivation of attention may

lead to a lack of situational awareness. Situational

awareness is defined as being aware of situation and

hazards around you and their effect on you, now and

in the future [12, 17]. Apart from losing focus on the

environment, overreliance on the automated system

may erode basic navigation skills, including

orientation and spatial knowledge, which is useful

when automation eventually fails [43]. Unfortunately,

in recent years large numbers of accidents were

caused by an overreliance on technology and the lack

of chronic unease. Accidents included overreliance on

ECDIS, Global Navigation Satellite System (GNSS)

and Automatic Radar Plotting Aid (ARPA), and

failure to use traditional navigation skills [56].

Obviously, overreliance on technology is problematic

Overreliance on ECDIS Technology: A Challenge for Safe

Navigation

M. Kristić

, S. Žuškin

, D. Brčić

& M.Car

University of Dubrovnik, Dubrovnik, Croatia

University of Rijeka, Rijeka, Croatia

ABSTRACT: The Electronic Chart Display and Information System (ECDIS) became the central navigational tool

on modern ships. The system comprises numerous navigational and other components, each of them with its

limitations and reliability. Due to ECDIS's revolutionary features, navigators are tempted to place excessive

reliance on the system. Such reliance on it as a sole navigational aid is undoubtedly a problematic issue. The

proposed paper is a segment of a systematically carried out research among ECDIS stakeholders. ECDIS EHO

(Experience, Handling, and Opinion) research aims through research activities based on a user-centred

approach to develop and improve the educational framework.

The overreliance on the ECDIS system motivated the proposed research, which focused on system users'

opinions and practice regarding confirmation of the accuracy of information displayed on ECDIS, particularly

concerning positional sensors. Analysis of answers collected by the ECDIS EHO questionnaire represents a

backbone of the research supported by previous achievements. The answers have been categorized and

discussed, revealing certain worrying aspects referring to the system's positional error experienced by users.

Furthermore, preferred methods of cross-checking ECDIS information have been identified and have differed

among respondents based on their rank on board. Additionally, answers indicate certain doubts between users’

interpretation of the best confirmation method and the actual selection of the used method. The importance of

cross-checking navigational data in avoiding overreliance and maintaining situational awareness has been

presented in the conclusion chapter and the proposal for further work.

http://www.transnav.eu

the International Journal

on Marine Navigation

and Safety of Sea Transportation

Volume 15

Number 2

June 2021

DOI: 10.12716/1001.15.02.02

278

even when all equipment is working correctly. As

equipment errors are inevitable, overreliance becomes

even more problematic. Cross-checking of

information obtained by single navigational aid by

visual, radar, or any other available means is

characteristic of a prudent navigator. Among all other

navigational aids, the possibility for overreliance on

ECDIS is probably the greatest. This is due to its

power of integrating, which differs it from any other

navigational system before. It is a navigational system

consisting of hardware and software incorporating a

great part of navigational equipment. In the ECDIS

context, this equipment is considered as sensors, not

as standalone devices.

This paper presents research conducted within the

project ECDIS EHO (Experience, Handling and

Opinion). The crucial part of the research is an

international questionnaire conducted among the

officers of the navigational watch. It considers their

experience and the capacity in which they are

engaged. This paper analyses the part of the

questionnaire that focuses on navigators' opinions and

practices regarding confirmation of the accuracy of

information displayed on ECDIS. This paper aims to

identify potential problems in using the ECDIS

system, focusing particularly on ECDIS overreliance.

The background chapter refers to the ECDIS general

aspects, concentrating on overreliance on ECDIS as a

complex system integrating a variety of navigational

aids. The survey methodology has been demonstrated

with the ECDIS EHO survey's general characteristics

and this paper's research interest. Results bring up

analyze of answers of a targeted group on questions

of interest of this research paper.

2 BACKGROUND

Integration of various navigational data received by

the navigational officer through visual observation

and from navigational instruments represents a

crucial part of safe navigation. Until recently,

navigators were integrating all received data

personally to complete the picture of the surrounding.

Filtered and integrated data were further used by the

navigator in the decision-making process. To assist

navigator, ECDIS integrates numerous navigational

instruments, becoming a focal system in safe and

efficient navigation [4, 9]. In fact, its real value is

defined by the synergy it provides [49]. According to

IMO performance standards, ECDIS should be

connected to positioning, heading, and speed source

[21, 26]. These sensors are called mandatory sensors as

they are required for the system's full operability.

Additional sensors include a great range of

navigational devices. Presently the most common

devices used to fulfil official requirements are satellite

navigation receiver (SNR) (ship’s position fixing

system, GNSS receiver), a gyrocompass, and a speed

and distance measuring device (Figure 1).

Figure 1. ECDIS layout [9]

Despite apparent benefits by integrating numerous

navigational instruments, there is a risk to supplant

traditional navigational routines, especially visual

observations. The false impression of technology

infallibility connected with poor situational awareness

and erosion of basic navigational skills have the

potential to cause an error and lead to ECDIS assisted

accidents. Officer of Watch (OOW) oriented to ECDIS

display, relying entirely on technology, and

neglecting visual observation through the bridge

window is undoubtedly a serious problem [7, 42, 58].

Cross-checking information by other navigational

means is the primary countermeasure for

overreliance. It serves to detect anomalies, and it is

considered a routine navigational procedure. To

constantly scrutinize information obtained by various

sources, OOW has a limited capability, especially in

confined waters. The substantial problem is that the

meaning of reliance is very abstract, and its value

cannot be measured. It is hardly possible for any

OOW to judge an adequate level of reliance, and if

OOW is expected not to trust technology, it will create

an abnormal professional and psychological

atmosphere [51]. OOW has no choice but to rely on

information provided by ECDIS, always considering

equipment limitations. Information provided by the

ECDIS system consists of information obtained by

sensors and cartography information provided by an

electronic navigational chart (ENC). Both categories

have their limitations, which could negatively affect

officer reliance on the ECDIS system.

Additionally, the system is vulnerable to cyber-

attacks, a relatively new factor affecting safety of

navigation. The increasing risk of cyber-attacks is

recognised by shipping industry; however industry is

not fully prepared in facing emerging challenges [3].

ECDIS and its typical back arrangement presents

perfect environment for cyber security threats

connected with malicious codes distribution [53].

Recognizing these limitations, it is possible to

address certain shortcomings and solve them through

the educational process. The risk of overreliance on

ECDIS and the necessity for training to avoid using

ECDIS as the sole reliable aid of navigation was

recognized by the Maritime Safety Committee [19].

Not only training but rather a wide range of activities

should be used to solve this issue. It is a matter of

long-term activities to create proper navigational

279

culture starting firstly from the educational process,

subsequently by meticulous onboard procedures,

supervision of OOW by the master, and finally

training.

3 OVERRELIANCE

3.1 Overreliance on sensors

Good seamanship requires some healthy scepticism

about each piece of equipment, however sophisticated

and precise it could be. Such scepticism is part of

what is known as chronic unease [15]. ECDIS system

is a complex system integrating a variety of

navigational sensors, each with its advantages and

disadvantages. Knowing the limitations of sensors

and controlling them is a prerequisite for safe usage of

the ECDIS system. System output can only be as

accurate as the information entered into it or

expressed as "garbage in – garbage out."

3.1.1 GNSS

ECDIS's fundamental advantage is that the ship's

position is continuously and automatically plotted on

ENC. Such a position is obtained mostly by GNSS, a

space-based system that has significantly changed

navigation history. The system first used onboard as a

standalone apparatus that provides accurate position

to be plotted on the paper navigational chart (PNC)

has become a hidden system feeding ECDIS with

position data. The best-known GNSS system is Global

Positioning System (GPS), but others are Russian

GLONASS or European Galileo. In normal operation,

GNSS/GPS will give a position accuracy of around 5-

10 m. In order to achieve improved accuracy within 1

m, a Differential GPS (DGPS) is used. DGPS is a

generic name for augmentation systems based on

ground stations, satellites, or can take the form of a

data service enabling fast acquisition of information

[53].

Overreliance on GNSS's position could be tracked

even to 1995, and the grounding of Panama flagged

passenger ship Royal Majesty [41]. This incident is

well known as an incentive to adopt the performance

standard for the integrated bridge system. The

incident root cause was the wrong position indication,

caused by a detached Global Positioning System

(GPS) antenna cable. Instead of GPS position, the

automated display showed a Dead Reckoning

Position (DP). As a result, Officers of Watch (OOWs)

were not aware of the actual position, which was 17

NM away from the assumed position. All navigating

officers were heavily reliant on GPS position and did

not use any method to cross-check position. Available

methods included position fixing by LORAN C,

presence of coast in vicinity detectable by radar, and

finally visual observations of fairway buoys. This

accident was caused by technical failure, but besides

system-related vulnerabilities of GPS, there is also

propagation and interference weakness. When

passing through an atmospheric medium, the signal is

vulnerable to disruptions, while large errors could

result from multipath.

Furthermore, GPS signals, due to their weakness,

are vulnerable to unintentional and intentional

interference, resulting in possible denial of service

over large geographical areas [16, 55]. Intentional

disruption includes jamming, spoofing, and

meaconing [28, 55]. Accordingly, numerous maritime

threats connected with GPS interference have been

reported in recent years over the regions affected by

political tensions [34, 35].

Since 1995 and the grounding of Royal Majesty,

GNSS has become even more important as a

navigation tool. Due to its great precision, reliability,

and simplicity, there is a considerable risk of

overreliance on GNSS [29]. Furthermore, it is

tempting for navigational officers to pass charted

hazards much closer than advisable [37, 40, 62].

ECDIS is heavily dependable on GNSS, used as the

primary position source on most of today's merchant

navy. Usage of secondary positioning source in ECDIS

system as redundancy is a matter of safety of

navigation. Regrettably, despite some possible global

positioning candidates, the secondary position source

is mainly the second GNSS receiver [8]. Two receivers

of the same global positioning systems are not an

ideal safeguard of position accuracy. Other than

secondary positioning source, the appropriate

countermeasure for overreliance on GNSS is using a

traditional line of position (LOP) and manual plotting

on ECDIS. This method serves as a verification of the

ECDIS position source. Position checking interval is

normally prescribed by the company ship

management system (SMS), where OOW has to cross-

check information obtained on ECDIS by other

methods. These methods include radar and visual

observations. The problem is that under normal

conditions, the position obtained by these methods is

far less accurate than GNSS, so we are using an

inferior method to cross-check the superior source of

position. [50]. The answer to that could be cross-

checking by several methods, rather than one, in order

to cross-check information obtained by ECDIS.

Relying only on GPS position as a sole navigation

technique without conjunction with other methods is,

putting it bluntly, bad seamanship. Such a growing

tendency endanger crew, ship, and her cargo [37].

3.1.2 Speed and measuring device

Accuracy of measurement of speed and distance

measuring device is prescribed by the International

Maritime Organization as 2% of the speed of the ship,

or 0.2 knots, whichever is greater [22, 24]. Such an

accuracy should not be a problem in open sea

navigation but could present an issue during

manoeuvring and docking a vessel. During

manoeuvring and docking, it is advisable to use fixed

objects at the shore to confirm vessel movement.

Additionally, advanced terminals handling large

tankers use a laser docking system, which provides

the distance to the berth and approaching speed [44,

57].

3.1.3 Gyro compass

A gyrocompass is an equipment that determines

the direction of the ship's head in relation to

geographic (true) north [20]. Besides classic electro-

280

mechanical gyrocompasses mostly found on the ships,

some new technologies are commonly known as

electronic compasses. Whatever type of compass

being used for heading source to ECDIS, it is

necessary to check it periodically to determine its

error [38, 40]. Control of gyrocompass error is

customarily done each watch, and after any major

change of course, and observed error must be

recorded in the gyro error book. This practice keep

navigator familiar with traditional navigational

routines, such as aligning two charted objects or

observing azimuths and amplitudes of celestial

bodies. Research by Lushnikov et al. conducted on

merchant navy ships reveals negligence in controlling

gyro error [45]. One of the prerequisites of a reliable

ECDIS display is correct information input by sensors,

and if gyro error is not frequently checked and

monitored, it could lead to unreliable display on the

ECDIS system.

3.1.4 Radar

After World War II, the radar's introduction in a

merchant fleet has caused a new category of accident

known as "radar assisted collisions" [52]. Expression

was first used to describe the collision between Italian

passenger ship Andrea Doria and Swedish liner

Stockholm that happened on 25th July 1956. As

overreliance on radar was a major cause of this

accident, this was followed by mandatory training for

the use of radar to become more systematized and

widespread [46]. Except for its role as a collision

avoidance tool, radar is useful as a device determining

a ship's position in coastal navigation. Several

methods by measuring bearings and distances from

conspicuous fixed objects are available. Among

others, the measurement of radar bearings and ranges

from a single conspicuous object is a quick and

effective procedure [8]. Additionally, to position

fixing by a radar system, there is a Parallel indexing

method, a method of cross-checking ship's path by

monitoring line parallel with the ship's route, mostly

used in confined waters. Finally, radar's significant

advantage is the independence of external sources, as

the system relies on its own detection of objects in the

environment. However, its performance is affected by

the meteorological conditions (clutter), false echoes,

size, and material of detected objects and land

features [38]. According to IMO performance

standards, radar system range and bearing accuracy

should be within than 1.0% of range scale used or 30

m, whichever is greater for range measuring, and

within 1˚ for bearing measurement [25].

Modern ECDIS system is interfaced with radar,

allowing duplication of radar image over the ENC.

This possibility is called Radar Information Overlay

(RIO). While radar image often has numerous

distortions, including radial and angular distortions

of the radar echo, several difficulties to detect

systemic distortions [33], RIO is still the most

immediate means of verifying ECDIS cartographic

data and the output of navigation sensors [32, 54, 60].

Furthermore, the RIO advantage is real-time and

efficient cross-checking, allowing OOW to detect a

mismatch between radar echo and ECDIS data easily.

A possible mismatch that can be revealed includes

cartography errors, GPS/GNSS positional errors, and a

Gyro heading error. Thus, RIO emerges as an efficient

and valuable tool for cross-checking data obtained on

the ECDIS system.

3.1.5 Automatic identification system (AIS)

AIS is an automatic reporting system designed to

improve the safety of navigation, by exchanging vital

navigational information between ships and between

ship and coast station. AIS system could be interfaced

with ECDIS system as an additional sensor and

connected to both radar and ECDIS on many modern

ships. There are several significant drawbacks of the

system: many small ships are not equipped with AIS,

it can be even switched off on ship’s master judgment

[23], or to cover illicit operations, causing the

interruption of AIS reception [39, 47], the received

reports can be unintentionally incorrect, jammed or

deliberately spoofed [23, 39]. Overreliance on AIS as a

sole navigational aid is extremely dangerous, as in the

collision between Rickmers Dubai and Walcon

Wizard. The investigation established that OOW on

Rickmers Dubai was relying solely on AIS

information displayed on the ECDIS as an aid to

collision avoidance [36].

Considering all the above mentioned, AIS should

be used as supplementary information only to

information derived visually and by radar. In that

case, when supplemented by other navigational aids,

it can be an important ‘tool’ in enhancing situation

awareness at sea [14, 23].

3.2 Overreliance on chart data

Recent groundings of Dutch freighter Nova Cura in

2016 and tanker Pazifik in 2018 serve as a reminder

that chart data reliability even on state-of-the-art

equipment is often questionable. Both ships run

aground due to unreliable ENC data [11, 13]. ENC

data reliability depends on the quality of chart survey

data, which in many cases are outdated and based on

a survey from the beginning of the last century. This

mainly goes to remote areas of oceans, where low

chart accuracy could be expected (Table 1). The ENC

survey data’s accuracy is expressed by the Zone of

Confidence system (ZOC), developed by the

International Hydrographic Organization (IHO).

There are five basic levels within the system differing

levels of quality, starting from “very high confidence”

to “unsurveyed” [18].

Table 1. Analysis of 14 million square kilometres of coastal

ENC [11]

_______________________________________________

Category Area Area Area Confidence

percentage percentage percentage

of English of Singapore of the

Channel & Malacca world's

Strait coastal ENC

_______________________________________________

A1 3.6% 1.4% 0.7% Very Good

A2 9.4% 0.2% 1,0% Very Good

B 62.9% 2.5% 30.5% Good

C 21.3% 76.2% 21.8% Fair

D 2.8% 1.1% 20.5% Low

U 0,0% 18.5% 25.4% Low

_______________________________________________

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Large areas of the world are still poorly surveyed,

reflected as some ENC's questionable accuracy.

Overreliance on ENC as a sole source of information,

without proper knowledge of the ZOC system, could

result in an accident. Passage planning should include

all sources of information available, including

navigational publications but local knowledge as well

where required. Needless to say, all information must

be timely updated, not only ECDIS but all other

sources of navigational information as navigational

publications.

Additionally, there still exists some ENCs derived

from PNCs that cannot be accurately referred to

WGS84 datum, generally used by GNSS and ECDIS.

Differences between positions obtained by the satellite

system and position on this cell could be significant

[61]. Mariner must always strive to cross-check

position by all available means when sailing in this

area.

4 PREVIOUS RESEARCH AND ECDIS EHO

SURVEY METHODOLOGY

The risk of overreliance on ECDIS was recognized as

an important safety issue a decade before its full

implementation on merchant ships [27, 31, 62], and it

is continuously emerging as a problem [2,48,63].

Several surveys from the early beginning of the ECDIS

system's implementation period, conducted as a

questionnaire among end-users, revealed that

overreliance is considered by users themselves as a

problematic issue. In [4] Asyali has shown the result

of a study performed among 230 Turkish Officers and

Masters between June 2008 and October 2011, which

have indicated that main officers’ objections with

regards to ECDIS usage are danger of overreliance on

ECDIS, overconfident and over relaxed officers,

degradation of navigational skills, reliability of the

system. Another survey [30] by Karnicnik conducted

between March and April 2005 aimed at officers’

opinion on using electronic charts. Results revealed

that officers consider overreliance on ECDIS as a

severe disadvantage. Research [5] by Bakalar et al.,

among 69 experienced navigators, reveals a similar

result, as respondents clearly said that ECDIS's use

degrades navigation skills and makes navigators

indulgent. As recent years have been marked with a

sequence of marine accidents that indicated ECDIS as

a contributing element, several researches which

analyzed mentioned accidents indicated overreliance

on ECDIS as a contributing factor to the accident. In

[1], Acomi analyzed several ECDIS-related maritime

accidents and have recognized that the causes of

accidents are results of overreliance on the system. In

a recent paper [59], Turna et al. used the 4M

Overturned Pyramid (MOP) model to analyze twenty-

two accidents related to ECDIS or ENCs and have

recommended that officers should cross-check

information obtained by ECDIS by other navigational

methods.

Overreliance on ECDIS as an essential issue was

recognized by ECDIS EHO research through different

surveys of navigators’ interaction with the system. In

[9], Brcic et al. studied the handling of the ECDIS

system by end-user. Over 500 marine accidents were

processed, and accidents related to ECDIS were

analyzed. Results have shown overreliance on ECDIS

as a significant factor in analyzed accidents, while

improper ECDIS use is pervaded through all the

cases. ECDIS acceptance after the completion of the

implementation period, as seen by Masters, was in the

focus of research [10] by Brcic et al. Among several

key points, there is a problem of overreliance,

decisively emphasized by masters, as most

experienced persons on board. In [8], Brcic et al. dealt

with the ECDIS system's positioning and reliable

secondary positioning source usage. Overreliance on

technology was identified as an important issue

together with non-usage of ECDIS secondary

positioning source and other issues arising from the

transition period. Again, overreliance as a serious

problem is recognized in research [6] conducted at the

end of the ECDIS transitional period. Finally, as

improvements of the education process and training

activities have been in the focus of the ECDIS EHO

project since beginning in 2014, the matter of proper

education and training with regards to the system

including excessive reliance on it has been raised in

previous researches [6, 64].

The survey initially arose as a questionnaire

distributed among attendees of ECDIS courses in the

year 2014. The data were collected internationally

until 2018 and impart insight into various issues

regarding ECDIS implementation on board merchant

navy. There are three types of questions contained in

the questionnaire. Introductory questions serve to

profile respondents according to their rank, seagoing

and ECDIS experience, and ECDIS education level.

The second set of questions is related to the handling

of the system with a particular focus on navigation

safety. Finally, the opinion of navigational officers on

ECDIS benefits and shortcomings is covered by the

last section of questions. ECDIS EHO research from

the beginning aimed at educational improvement by

analyzing specific topics pertaining to the project's

theme. Navigational officer as end-user is in a central

point of research, providing feedback, generating

findings, and sometimes showing different

perspectives on the subject. This paper simultaneously

analyses two closely related questions regarding

confirmation of the accuracy of information displayed

on ECDIS and experience with position mismatch on

the ECDIS system. Among all information sources

connected to ECDIS, GNSS as a positional source

requires the most attention. It is due to its

vulnerability, history of overreliance, and insufficient

redundancy. Insight about officers’ confirmation

methods and practice to avoid dependence on ECDIS

as a sole navigational aid and their experience with

position reliability on ECDIS is given by an analysis of

the following questions:

1 1. Have you encountered position

mismatch/offset/error or any other problem related

to position display on the ENC? If YES, please

explain the case/s.(Q1)

2 2. What is the best confirmation of the accuracy of

information displayed on the ECDIS system (circle

and, if you think it is relevant, write and explain

the answer)? a. Radar; b. Visual observation; c.

Something else. (Q2)

Q1 consists of two parts. In the first part, besides

YES/NO answers, a N/A (not applicable) answer has

282

been introduced for ambiguous or blank answers. The

second part of Q1 clarifies positive answers, which

could be further categorized and elaborated.

Q2, as an answer, offers a choice of Radar, Visual,

or another method of accuracy confirmation.

Respondents have had the opportunity to explain the

answer closely, which is further elaborated.

5 RESULTS

The International EHO Survey contains responses

from 350 respondents: 99 Masters (M), 77 First mates

(1/O), 66 Second mates (2/O), 13 Third mates (3/O), 8

Staff captains (SC), 1 Marine safety consultant (MSC),

3 Safety officers (SO), 3 Environmental officers (EO), 4

Dynamic positioning operators (DPO), 1 pilot (P), 1

superintendent (SI), 1 supervisor (SV), 14 port State

control officers (PSCO), 25 trainees (T), 1 Yacht-

Master (YM) and 33 persons of unspecified position

making part of the navigational watch (U) (Figure 2).

3 3

1 1 1

100

120

Figure 2. All ECDIS EHO survey respondents

As a subject of this paper is the overreliance of

active users of the system, it was required to filter

respondents to a representative sample. Filtering was

done by using introductory questions, which were

used to distinguish the target group from the initial

sample (Figure 3). In the first stage (FS) of the survey,

respondents with no ECDIS experience were removed

from the sample. In the second stage (SS) other ranks

except for Master, Staff Captain, First Officer, Second,

Third Officers, and Trainees were excluded, as well as

a respondent with missing data with regards to

profile-defining introductory questions. In the third

stage (TS), respondents whose job profile does not

include working with ECDIS were excluded as well.

Finally, it gave us a total of 208 respondents who are

actively using ECDIS and have previous experience

with the system.

Finally, it gave us a total of 208 respondents who

are actively using ECDIS and have previous

experience with the system. Shares of target group

respondents according to their rank is presented in

Figure 4.

Figure 3. Target group selection stages

30.8%

2.9%

26.4%

27.9%

4.8%

7.2%

1/O

2/O

3/O

Figure 4. Target group respondents’ shares

The general share of answers on the first part of Q1

is shown in Figure 5. Most respondents did not

experience position mismatch on ENC (48%);

however, the share of respondents that encountered

position error is remarkably high (37%).

37%

48%

15%

Yes

N/A

Figure 5. General share of answers (Q1 – first part).

Analysis of the second part of Q1 deals with

respondents that positively answered the first part of

the question. Circumstances behind experienced

problems with regards to position display on ENC are

clarified in this part (Figure 6). Comments are

clustered into four groups that are based on typical

answers from respondents:

− Offset determination method

− Offset cause

− Offset geographic area

− Unclear

283

The offset of position is possible to determine by

comparing ECDIS primary position obtained by GNSS

and ideally secondary independent source, or by

position plotted using LOP obtained visually, by

radar or another available mean. Additionally, offset

could be recognized by comparing ENC cartography

with RIO, but the exact value cannot be determined

without position fixing. The offset cause could be a

result of sensor error or cartography issue. The offset

geographic area provides details of the area where the

error occurred. Some respondents even providing a

positive answer to the first part of Q1, did not provide

any explanation in the second part. These answers are

gathered into section Unclear, together with indefinite

answers. In comparison, some respondents explain

the case by the method of offset determination; other

states possible causes of the incident or area where the

incident occurred. Furthermore, some respondents

provided answers belonging to more than one group.

Determination method

Cause

Geographic area

Unclear

Figure 6. General share of answers (Q1 – second part).

Each group of comments is further analyzed

(Figure 7). Analysis discovers that respondents

explaining the method of offset determination have

mostly used radar (53%), while from the rest of the

answers, it is not clear what method was used to

recognize offset. The major share of respondents that

mentioned cause of offset identified chart accuracy or

wrong datum as a cause of position offset (39%),

followed by Lost GPS signal (35%) and GPS & Gyro

error (17%). Among respondents that identified the

incident's geographical area, most of them

experienced that issue in South America (40%)

followed by other areas.

Figure 7. Answers' categories on the cause, determination

method, and geographic area (Q1 – second part).

Figure 8 shows the general share of answers to Q2.

Results clearly illustrate almost the same percentage

of answers between radar (31.7%) and visual (30.8%)

confirmation of information displayed on ECDIS.

Active users of the system find both options equally

valuable. Interestingly the roughly same percentage of

respondents choose a combination of radar and visual

confirmation (30.8%) as their choice, even the question

was to specify the best method.

Logically best method can be only one, but clearly,

navigators cannot decide which method is better or

find them complementary. These two methods, alone

or combined, give 93.3% of answers. Other answers

with minor frequency include confirmation by GPS

(1.4%), radar, visual and echosounder (1.0%), radar

and GPS (0.5%), and undefined answers (3.8%).

Furthermore, to get a better insight into the survey,

the target group was divided into three major

subgroups: Masters (include Masters and Staff

Captains), Officers (include Chief Officers, 2nd

Officers, and 3rd Officers), and Cadets (Figure 9).

Figure 8. General share of answers on Q2

34%

59%

Masters Officers Cadets

Figure 9. Target subgroups’ shares

Methods of confirmation of accuracy are the same

as above: radar (R), visual (V), Radar & Visual (R&V),

GPS, Radar & Visual & Echosounder (R&V&E/S),

Radar and GPS (R&GPS), Undefined (U). The result

reveals differences and similarities between

subgroups (Figure 10). While Masters prefer radar

more than visual, officers declare both methods

equally important. The cadets' group has significantly

less confidence in radar as a source for cross-checking

compared to the other two groups and equally choose

visual confirmation and a combination of radar and

visual.

284

20%

40%

60%

80%

100%

Masters Officers Cadets

R V R & V

GPS R & V & E/S R & GPS

Figure 10. Results on Q2 for target subgroups

It is important to note that all three groups have

almost the same percentage for the sum of the first

three methods, i.e. radar, visual, and radar and visual

methods.

6 DISCUSSION

Considerable problem is revealed by results of Q1,

showing a significant share of respondents that have

encountered a problem with position mismatch on

ECDIS. As much as 37% of respondents experienced a

serious near miss, which can cause a catastrophic

accident. Position error was observed using a radar in

53% of cases, proving that radar and RIO are the most

favoured method of cross-checking. Significantly, for

the remaining 47% of answers, it is not clear what

method was used to recognize offset, so there is a

possibility that shares of errors observed by radar are

even larger than 53%. Detailed analysis of offset

causes discovers that more than a half respondent

(52%) explaining the cause of the offset mentioned

GPS as a source of trouble. This is expected as GPS is

the main source of position information to the ECDIS

system. This fact particularly emphasizes the need for

ECDIS secondary position source other than GNSS.

The major group (39%) mentioned chart accuracy or

wrong datum as the cause of position offset. Results

on Q1 stress the necessity of frequent cross-checking

of ECDIS information, especially in the coastal area,

where routine navigational methods are easily

available. All three significant causes of position offset

are easily recognizable by position cross-checking and

using a visual and radar confirmation, but only in the

coastal area. Answers do not provide information if

any of the position mismatches were detected at the

open sea. Results of Q2 recognize radar (31.7%) as a

preferable system, closely followed by visual

confirmation (30.8%) and a combination of radar and

visual (30.8%). A minor number of participants

mentioned other methods, such as GPS and

echosounder. As GPS is the main source of positional

information to ECDIS, it makes no sense to control

ECDIS by GPS. Echosounder is one of the possible

methods, but hardly the best one. None of the

respondents mentioned astronomical navigation as a

possibility to assess the accuracy of ECDIS

information at the open sea.

Among all groups, Masters, as the most

experienced group, prefer radar significantly over

visual observations, which is in line with the research

of Šakan et al. (2018) [50]. Cadets, as the least

experienced group, evaluate the visual method with

the highest rank. Officers, as the most represented

group, find both methods equally important. It seems

that radar preference goes hand in hand with

experience. Finally, Q2 provides a valuable outcome,

as, despite the question which was targeting the best

method of confirmation, a significant number of

respondents choose a combination of methods.

Clearly, the system's active users are aware of the

necessity to check position by all available means

available. Indeed, no method is perfect, so a

combination of methods to establish situational

awareness is good seamanship practice.

Nevertheless, the results of Q1 with regards to the

actual offset determination method where most of the

respondents that explained their experience used

radar to cross-check position on ENC does not fully

support answers from Q2. When asked about the best

method of confirmation, the same respondents choose

radar and visual observation as almost equal, but

none of the actual discoveries of position offset in Q1

was by visual method, or it was not clearly

mentioned. Does it mean that even respondents

consider both methods equally good, prefer using

radar confirmation in practice due to its feasibility?

Social-desirability bias is another explanation, i.e.,

respondents may tend to give answers which are

more acceptable to the community. In the case of Q2

visual observation is a favourable answer as it is

considered a prime navigation technique. In fact,

radar cross-checking is a more practical method,

providing instant information on possible

presentation errors. Visual observation is generally

less practicable than radar observations except in

narrow spaces like port areas or channels.

Several findings were observed:

− Position error is a frequent occurrence.

Fortunately, it can be detected in coastal navigation

by using available traditional cross-checking

methods.

− Position error is mostly noticed by the usage of

radar.

− Visual and radar confirmations of ECDIS

information accuracy are equally graded cross-

checking methods, but it seems that users in

practice detect anomalies by radar usage.

− Experienced navigators favour radar over visual

observations for confirming ECDIS information

accuracy.

Considering identified observation, a conclusion is

that radar is a navigational instrument mostly used to

assess ECDIS information accuracy, despite its

constraints. The conclusion further highlights the

necessity of ECDIS secondary position source such as

a hyperbolic navigational system, which would

significantly improve the confidence in the ECDIS

system.

A flow diagram showing the progression of

positional error is presented (Figure 11). Positioning

errors affecting situational awareness could be

categorized as system errors and human errors. While

system errors result from sensor error, ENC

285

cartography, or poor bridge layout, human errors are

affected by the experience, training, knowledge, and

navigational skills. By cross-checking, possible errors

are confirmed, rectified, and situational awareness is

established once again. Poor or no cross-checking at

all leads to overreliance, perilous situations where the

navigator has a dull sense of control over the

situation, while in fact, control over the ship is lost.

Cross-checking is the most important way to

control overreliance and hold a grip on situational

awareness, but it should be done with all available

means, not relying on one method only. Raising

awareness among navigators through educational

activities to keep them always positively suspicious is

crucial. Recognizing own and system limitations

actively raise navigator’s awareness, counteract

overreliance, and positively affect the safety of

navigation.

Figure 11. Flow diagram of overreliance effect on situational

awareness

7 CONCLUSIONS

The proposed paper deals with an overreliance on

information obtained by the ECDIS system,

specifically on information obtained by position

source. The survey is supported by the international

questionnaire. The questionnaire was conducted in

the period from 2014 to 2018, during the second half

of the ECDIS implementation period. The research

aimed to identify the frequency and details of wrong

position indications on ECDIS and the preferable

ECDIS information cross-checking method. The

answers from the target group were analyzed and

discussed. The findings indicated that the position

error on the ECDIS system is relatively frequent,

which entails potential high risks regarding

navigation safety. According to answers, GPS errors

are the leading cause of position deviations on ECDIS,

which is expected considering that GPS is the primary

source of position data to ECDIS.

Confirmation of ECDIS information accuracy or

cross-checking is performed by radar, visual

observation, or other available navigational means.

While visual and radar methods are almost equally

rated methods for confirming the accuracy of the

information, answers revealed that in practice, radar

is used more to detect deviations. Moreover, more

experienced navigators prefer radar over visual

observation. Despite obvious radar advantages in

terms of practicality, there are still some limitations of

the radar system that navigator must recognize. A

desirable solution to overcome ECDIS positional

accuracy failures could be a secondary position source

other than GNSS.

The fact that a significant number of respondents

are choosing more than one method to confirm the

accuracy of information denies degradation of

navigational skills so far. Educated and experienced

navigator stay alert even when everything looks

perfect and recognize the appropriate cross-checking

method depending on circumstances. Considering the

abovementioned, a key answer is a proper educational

framework customized for new generations of

navigators handling new technologies. By using cross-

checking, the navigator can detect eventual errors,

rectify them, and gain situational awareness.

Contrary, without cross-checking, the navigator

becomes over-confident on instruments, and

consequently, situational awareness is lost.

Future work will consider other significant ECDIS

information sources that could affect situational

awareness by over-relying on them.

ACKNOWLEDGMENTS

This study represents the continuation of the ECDIS EHO

project and research. The authors are grateful to all the

navigational ranks, officers of the navigational watch, and

other ECDIS stakeholders for their time and willingness to

complete the surveys, and participate in discussions. The

authors believe that their responses and opinions have an

immense significance for the appropriateness of the

research deliverables.

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