International Journal

on Marine Navigation

and Safety of Sea Transportation

Volume 5

Number 1

March 2011

1 INTRODUCTION

The year 2012 will be the first year of mandatory in-

stallation of the Electronic Chart Display and Infor-

mation Systems (ECDIS) onboard ships. The first

installation requirements refer to newly built vessels,

depending on their type and size. Then in the years

2016-2018 the regulation will come in force for

ships in service. The navigator of the vessel under

the mandatory requirements of the SOLAS Conven-

tion will receive an essential tool changing the rules

of navigation, watchkeeping and assessment of

ship’s safety. This tool has alarm and indicator func-

tions that provide important aid to the navigator. Its

proper use requires a valid user-defined parameters

of safe navigation and activation of selected alarms.

A large number of applicable safety features causes

difficulties in its use in navigation along a desired

route. Therefore, it is advisable to specify a group of

basic safety parameters as a minimum for the plan-

ning and safe monitoring of sea passage.

The analysis of alarms and related safety parame-

ters was carried out on with ECDIS NaviSailor

3000i device by Transas Ltd. (Transas, 2004a,

Transas, 2004b, Grzeszak et al. 2009)

It should be noted that not all alarms and safety

parameters dealt with are mandatory according to

the performance standards for ECDIS systems (IMO

Resolution A.817/19 1995, IMO Resolution

A.232/82 2006, Weintrit 2009). Some of them are

introduced by manufacturers of such systems as part

of enhancing their functionality.

2 ALARMS IN ECDIS

2.1 Types of alarms

There is a large number and variety of alarms, so

they can be classified according to various criteria.

The authors propose the division of alarms accord-

ing to these criteria: 1) priority of the alarm, 2) pos-

sibility of activation and deactivation, 3) source, 4)

the scope of the alarm, and 5) basic / others.

The first criterion divides the alarms into: a)

alarms, b) indications . This division results from the

provisions of IMO Resolution A.817(19), A.232(82)

and IMO "Code on Alarms and Indicators" (IMO-

867E). The state of the system requiring attention

and action is signaled by an alarm in the form of

acoustic or acoustic and optical signal. The state of

the system requiring attention mainly of the user,

without having to take immediate action, is indicated

in the form of an optical indication only.

Among alarms implemented in ECDIS system the

following are distinguished (criterion 2): a) the

alarms that cannot be deactivated (e.g. Safety Con-

tour, Depth Safety), b) alarms that can be deactivat-

ed (e.g, Sounder Depth, Anchor Watch), c) alarms

that can be deactivated, but the user responsible for

the safety protects them with a password. These

alerts are activated in different ways, and some re-

quire implementation of the safety parameter in ad-

vance.

The division of alarms due to the source (criterion

3) includes alarms by: a) hardware, sensors) b) sys-

tem. The former signal states of disability or reduced

functionality of devices, including sensors of the

Navigation Safety Assessment in the Restricted

Area with the Use of ECDIS

Z. Pietrzykowski & M. Wielgosz

Maritime University of Szczecin, Szczecin, Poland

ABSTRACT: This paper presents an analysis of vessel safety parameters used in the ECDIS system while

navigating in restricted areas. Apart from defining their priorities, a group of parameters indispensable for the

safe navigation in restricted waters is identified.

The function of ship domain is proposed on the basis of safety parameters defined in the ECDIS system. This

function may be utilized in the navigation decision support system that uses ECDIS data and included as a

new function in the ECDIS system.

system and the system as a whole, such as network-

ing. The other group contains alarms associated with

the implementation of functions relating to naviga-

tional situation. They signal a significant event for

the safety of navigation.

The fourth division includes the proposed classi-

fication of alarms according to the criterion of scope

of activities. This term is understood as the functions

of alarms associated with the types of threats. These

can be distinguished: a) antigrounding alarms b)

alarms associated with the route of the ship – “Route

alarms” c) Target / Radar alarms d) Area type alarms

or "Area alarms" , e) other alarms; f) AIS alarms g)

alarms and indications related to the scale and type

of the chart.

Experiments conducted at the Maritime Universi-

ty of Szczecin during model ECDIS courses, result-

ing in issuing the ECDIS operator's certificate, show

that course participants do not use many system ca-

pabilities, and also have problems with the interpre-

tation of alarms and indications. This is mainly due

to the different specifics of the work on the ENC as

compared to working with paper or raster charts.

Lack of understanding by the operator of the princi-

ples of interpretation of ENC content by the ECDIS

system results in significantly reduced utilization of

the system, and even the use inconsistent with the

idea of the system. This involves the use of ECDIS

system on the principles applied to classical paper

charts, where interpretation of the contents of the

chart lies belongs to the user only. It is connected

with the fact in that during the process of navigator

training primarily paper charts are still used. A better

use of ECDIS systems requires, therefore, wider use

of ENC in the training of navigators.

Table 1. Alarms classification criteria

_________________________________________________

Criterion

_________________________________________________

Alarm type Activation/ Source Scope of Priority

deactivation activities

_________________________________________________

1 2 3 4 5

_________________________________________________

a) alarm deactiv. equipment, anti- basic

impossible sources groun-

ding

_________________________________________________

b) indication deactiv. system route other

possible

_________________________________________________

c) deactiv. target

possible

(password-

protected)

_________________________________________________

d) area alarms

_________________________________________________

e) others

_________________________________________________

f) AIS alarms

_________________________________________________

g) chart alarms

_________________________________________________

Significant help in the correct use of the system

may be an additional division and allocation of

alarms and indications (criterion 5): a) basic alarms

and indications, necessary for safe voyage monitor-

ing b) other, complementary to the previous one.

These criteria and the classifications of alarms are

summarized in Table 1.

2.2 Basic and other alarms

Taking into account the above, an analysis of alarms

and indications was performed according to the cri-

terion of ECDIS scope of activities (criterion 4),

with the proposal and explanation for the division

into basic and other alarms (criterion 5).

The alarms in question are presented in Table 2.,

categorized by the groups of alarms identified in the

ECDIS NaviSailor 3000i system.

Table 2. Groups of alarms according to the presented criteria

(see Table 1).

_________________________________________________

Group of Location Criterion

alarms/ (ECDIS 1 2 3 4 5

indications NaviSailor

3000i)

_________________________________________________

antigroun- monitoring/ a, b

a, b, c

b a a

ding alarms nav. alarms

______________________________________

system a, b

a, b, c

b a a

_________________________________________________

route monitoring/ a a, b

a, b

alarms route mon.

______________________________________

system a a, b

a, b

_________________________________________________

target/ targets/ a a, b

a, b

a, c

a, b

alarms ARPA

______________________________________

system a a, b

a, b

a, c

a, b

_________________________________________________

areas/ monitoring a a b d a

basic areas nav. alarms

_________________________________________________

areas/ monitoring a a b d b

add. areas nav. alarms

_________________________________________________

other monitoring/ a a b e a, b

alarms nav. alarms

______________________________________

system a a b e a, b

______________________________________

config. a a b e a, b

_________________________________________________

AIS alarms alarms/ a a b d a

AIS alarms

_________________________________________________

chart system a, b

b b g a, b

______________________________________

alarms charts a, b

b b g a, b

______________________________________

monitoring. a, b

b b g a, b

_________________________________________________

due to the diversity of alarms in the group, it was necessary

to assign some of them to more than one group according to the

criterion.

The group of "Antigrounding Alarms" contains:

a) Nav. danger, b) Safety contour changed, c) An-

chor watch, c) Safety contour, e) Safety depth, f) Ag

monitoring off, g) Safety scale changed.

The group of "Route Alarms" contains: a) Off

chart, b) End of route, c) Out of XTE, d) Behind

schedule, e) Ahead of schedule, f) WP approach, g)

Course difference, h) Prim / Sec diverged, i) Chart

datum unknown, j) Prim. not WGS 84, k) Sec. not

WGS 84, l) Track control stopped, m) Backup navi-

gation, n) Low speed, o) Dangerous drift, p) Course

change.

The group of "Target / Radar Alarms" contains:

a) CPA / TCPA, c) Lost target, c) Guard zone tar-

get, d) Disk full save reset, e) Disk full adjust save,

f) Head marker failure, g) Bearing failure, h) Trigger

failure, i) AIS message.

The group of alarms "Area Alarms” contains 28

"Basic Areas” alarms and 14 “Additional Areas "

alarms.

The group of "Other Alarms" contains: a) Timer

went off, b) End of watch, c) Time zone changed, d)

No official chart, e) Add info warning, f) Add info

chart full.

The group of "AIS Alarms" contains: a) Tx mal-

functioning, b) Antenna VSWR exceeds limit, c) Rx

channel1malfunctioning, d) Rx channel 2 malfunc-

tioning, e) Rx channel 70 malfunctioning, f) general

failure, g) MKD connection lost, h) External EPFS

lost, i) No sensor position in use, j) No valid SOG

information, k) No valid COG information, l) Head-

ing lost / invalid, m) No valid ROT information.

The group of "Chart Alarms" contains: a) Dan-

gerous scale, b) Not recommended scale, c) Layers

lost, d) Look up for better chart, e) Larger scale

chart available, f) ENC data available, g) Chart pri-

ority / HCRF mode, h) Safety scale / check on larger

scale than, i) No official chart (also included in

“Other Alarms”.

Basic alarms are considered as alarms which are

important for the safety of sea passage. Among oth-

ers, they include: commonly used collision warning,

sounder depth alarm, lost target, cross track error -

XTE. The newly introduced alarms for ECDIS sys-

tems which work on the basis of vector charts were

considered as important. These include safety con-

tour, safety depth, area alarm, navigational danger.

Selecting the basic alarms may facilitate their ac-

tivation, and editing the safety parameters associated

with them.

3 NAVIGATION SAFETY PARAMETERS

The effectiveness of alarms depends on the proper

definition of safety parameters associated with them.

These efforts should include the nature and circum-

stances of the area of navigation. A necessary condi-

tion is also their selective activation (except for sys-

tem alarms), taking into account the type of area and

navigational situation. Another problem, not ana-

lyzed in this article, is the selection of alarms to be

activated reflecting the experience and knowledge of

a specific sea area by the navigator.

The analysis highlights the safety parameters as-

sociated with the movement of the vessel on the sur-

face and in the third dimension - depth and underwa-

ter hazards.

3.1 Navigation safety parameters associated with

the movement of the vessel on the water surface

These parameters apply to both fixed and mobile ob-

jects that threaten the safety of navigation, also in-

cluding parameters related to the navigation accura-

cy and maintaining the vessel's position and route.

CPA, TCPA. The basic parameters of this group

are the Closest Point of Approach (CPA) and Time

to Closest Point of Approach (TCPA), edited by the

navigator and activating collision warning alarm.

They cover both AIS targets (if the presentation is

switched on) and the radar / ARPA objects. When

the ARPA is connected to the ECDIS as its sensor,

the limit values of these parameters can be edited in-

dependently in the ECDIS and the ARPA. In this

case, the ARPA is treated as a system sensor for the

ECDIS, which means that the alarm from system

ARPA must be repeated in the ECDIS system.

Guard Ring (Rings), Guard Zone (Zones). Im-

portant safety parameters are the radius of the area

of automatic acquisition or parameters that define

the zone or zones of automatic acquisition. In the

latter case they may be the values of angle sectors

with inserted distance from the unit. These parame-

ters, similarly to the parameters of CPA and TCPA

can be edited independently in the ARPA and the

ECDIS.

Area Vector. This is a vector representing time

from the intersection of area type objects. Time set-

ting, selected by the navigator, is represented as a

vector calculated on the basis of a calculated COG

and SOG. It may be displayed together with the

Safety Vector. The navigator has a choice of area

objects. The selection of area objects should be done

depending on the crew experience and knowledge of

the sea area.

RMS Circle (Root Mean Square Error Circle - at

95% confidence level). The parameter is calculated

automatically by the system, but the novelty of in-

creasing its relevance and practical use in ECDIS is

introduced in a graphical presentation of the circle

and the expected trajectory. This allows to verify the

setting of parameter XTE.

Limit of Cross Track Error - XTE. This parameter

is independently defined by the navigator to the left

and right side of the route and may be different at

each leg of the route. Its importance lies in the fact

that it determines the width of the ship trajectory

checked by the system (by using the "Check" func-

tion, checking whether the planned route exceeds or

not the safety parameters set by user. Importantly,

the automatic system " Track Control " (mandatory

in ECDIS) will try to keep the ship within this limit.

Divergence in the primary and secondary posi-

tioning system. This parameter allows the navigator

to monitor the difference in position of the vessel

obtained from two positioning systems (generates

optional alarm “Primary / Secondary Diverged”). In

addition to activation, the user sets a limit of the dis-

tance at which positions from the main and second-

ary positioning systems can diverge.

Parameters related to the monitoring of the ship's

planned route. These are course difference, WP ap-

proach, out of schedule, off chart, last WP passed.

Incorrect setting of these parameters may cause a

navigational accident.

Parameters describing the activation of functions

related to charts to be used: priority of loaded charts

(Chart Priority), and automatic chart loading "Chart

Autoload". Improper use of these features can result

in a lack of alarms specific to the ECDIS system

(working with the charts other than ENC S-57

standard charts).

3.2 Navigation safety parameters associated with

underwater hazards

Safety Contour. This parameter, defined by the nav-

igator, is one of the most important safety parame-

ters of modern navigation. The parameter possible

for use in ECDIS only when the system uses vector

charts. It generates an alarm of intersecting the safe-

ty contour. If the chart does not have a selected safe-

ty contour in its database, the system automatically

sets the next higher (safer) contour.

Safety Depth. Parameter defined by the navigator.

It extends the ability to detect underwater hazards

found at depths greater than specified by safety con-

tour.

Time from the intersection of safety contour -

Safety Vector. The parameter is defined by the navi-

gator. It allows designation and presentation of the

"Safety Vector" on the basis of calculated COG and

SOG.

Sounder Depth. Parameter defined in the echo

sounder as a sensor of ECDIS system. This means

that the alarm will be repeated in the ECDIS system.

This allows the verification of depth, read from the

ENC.

Navigational danger ring radius. It defines a cir-

cle of safety "Navigational Danger Ring". This ena-

bles the detection of underwater hazards on the basis

of ENC. It also allows detection of: a) Navtex ob-

jects that have the attribute "Danger" added, b) ob-

jects inserted by the user as "User chart object" or

"Manual correction object" which was given the at-

tribute "Danger" and / or inserted depth less than the

"Safety Depth ".

3.3 Other safety parameters

Safety scale. Parameter defined by the user. It de-

termines the chart scale for checking safety contour

and safety depth. It means that the system will moni-

tor underwater hazards on charts with a scale larger

than that determined (Fig. 1).

Differential mode lost. The time for which signal

is lost from the DGPS reference station. The excess

value of this parameter generates an alarm. This is

important because of the decline in accuracy of fix-

ing the position from DGPS to GPS.

Display category imaging. This parameter defines

the scope of the presented on-screen navigation in-

formation: Base, Standard, Custom, All.

Shallow Contour and Deep Contour (Fig. 1). The

parameters are defined after the function “Four

Shades” is activated to present additional areas of

shallow water (Shallow Contour) and deep water

(Deep Contour). The function modifies the displayed

chart by creating four depth areas with different col-

ors.

Fig. 1 Safety parameters window (safety contour, safety depth

and safety scale)

3.4 The basic safety parameters

The analysis of alarms and safety parameters, their

location in the ECDIS system and the consequent

difficulty of access to them makes it advisable to in-

troduce the function “Basic Safety Parameters Set-

tings”. This function would allow the operator, in

one tab or window, to define and monitor the basic

safety parameters, and activate alarms necessary to

ensure safe voyage realization by the ship equipped

with ECDIS. It should include viewing and editing,

and the activation state of alarm associated with

them. These are:

1 safety contour,

2 safety depth,

3 safety scale,

4 chart display category,

5 „chart priority”,

6 CPA/TCPA,

7 cross track error – XTE,

8 course difference,

9 WP approach,

10 safety vector (advance in the intersection safety

contour),

11 area vector (advance in the intersection of area

objects),

12 Navigational Danger Ring, its radius,

13 chart display and ship’s motion (North Up,

Head Up, Course Up, Relative Motion, True

Motion)

14 difference in the position of the vessel from

primary and secondary positioning system

(Primary / Secondary diverged),

15 presentation of AIS targets (on / off),

16 presentation of ARPA objects (on / off),

17 special areas detecting defined (yes / no),

18 presentation of the COG (course over ground)

and COW (course over water) vectors (on /

off),

19 off chart (on / off).

Before the start of a voyage or when the system is

restarted, ECDIS should automatically require the

operator to define or confirm the values of these

safety parameters with the possibility of automatic

switch to the window where the operator activates

and edits that alarm.

4 SHIP DOMAIN

4.1 Ship domain as a safety criterion

Safe operation of the ship requires constant analysis

and evaluation of the situation. On this basis naviga-

tor undertakes decisions concerning navigation. The

analysis and assessment of the situation are carried

out in accordance with the criteria adopted by the

navigator. A commonly used criterion in collision

avoidance systems is the closest point of approach.

However, in the case of navigation in restricted wa-

ters, particularly in narrow fairways and channels, it

is difficult to apply in most cases. This is due to the

lack of free choice of route and the need for compli-

ance with safety rules, taking into account local con-

ditions (restriction of one of the three dimensions

defining the distance of the ship from other objects).

An alternative to the mentioned criterion of the

navigational safety is the criterion of the ship do-

main. Application of the criterion of ship domain

enables quick identification and assessment of the

navigational situation and thus developing the deci-

sion support in ship’s maneuver. It should be noted

that this criterion is also possible to use in the open

sea areas. For example, this criterion was imple-

mented in the prototype of navigational decision

support system for seagoing vessels developed at the

Maritime University of Szczecin (Pietrzykowski et

al.2009).

The concept of ship domain was introduced in the

1970s (Fuji & Tanaka 1971, Goodwin 1975). It is

assumed that the domain is an area (domain two-

dimensional) or space (three-dimensional domain)

around the vessel which should be kept clear of oth-

er objects.

Assuming a certain level of discretization of rela-

tive bearings (eg

∆∠

K = 1° ), the domain boundary

of the vessel B

is described by a curve passing

through the n points p

(i = 1,2,..., n), located on the

relative bearings

∠

at the distances d

DSKi

from

centre of the vessel (eg, centre of waterline):

{ }

DnDDDS

p...,,p,pB

(1)

Ship domain boundary D

at different bearings is

then described as follows:

( )

n,...,,idKD

DSKiiS

21=≤∠

(2)

The basic problem is to define the domain bound-

ary, dividing the area around the ship into sub-areas:

dangerous and safe. It is a difficult task because the

shape and size of the domain are affected by many

factors. These include: size and maneuverability of

the vessel, parameters of the area where the ship

maneuvers, hydro-meteorological conditions, vessel

speed and the speed of other vessels, the intensity of

vessel traffic in the area, the accuracy of position

fixing, training level, knowledge and experience of

navigators. Also significant is the adopted method of

determining the ship domain boundary.

The issue of determining the domain was present-

ed in many publications, including (Fuji & Tanaka

1971, Goodwin 1975, Coldwell 1983, Zhao et al.

1993, Smierzchalski & Weintrit 1999, Pietrzykowski

2008, Pietrzykowski & Uriasz 2009, Wang et al.

2009). There are two-and three-dimensional do-

mains proposed in the literature. The former de-

scribe the area around the ship. Domains of two-

dimensional shapes include circle, rectangle, ellipse,

polygon, complex plane figures. In the case of three-

dimensional domains - they describe also vertical

space included between ship and sea bottom and the

air draft of the ship. Their shape often corresponds

to sphere, ellipsoid, cylinder, truncated cone.

Among the methods of determining the ship do-

main one can distinguish three groups: statistical

methods, analytical methods and artificial intelli-

gence methods. It is characteristic for all these

methods that they make use of navigators’

knowledge, both procedural and declarative.

Application of statistical methods requires the

registration of relevant data. In addition to difficul-

ties in collecting them, the problem that arises is to

separate various factors that influence the shape and

size of the domain.

Analytical methods are based on the analytical

description of the domain space. These methods en-

sure precise description of the ship domain. The

main difficulty is to take into account and balance all

relevant factors affecting the shape and size of the

domain.

Methods of artificial intelligence (AI) were de-

veloped to acquire and use the knowledge of expert

navigators using the tools of artificial intelligence.

They include and use, inter alia, fuzzy logic, artifi-

cial neural networks and evolutionary algorithms.

4.2 Possibility to define a domain based on the

safety parameters in the ECDIS

Safety parameters available in the ECDIS system do

not define directly a ship’s domain. These authors

analyzed the possibility of identifying the two-and

three-dimensional domain using the parameters ana-

lyzed in the article. The problem was brought down

to the determination of the length, width and shape

for two-dimensional domain, and in the case of

three-dimensional domain additionally the depth and

shape of the geometric solid.

If we use the CPA parameter value to determine

the length of the domain D

then the length of the

domain takes the value

=2CPA (3)

This results from the fact that this parameter de-

fines a safe distance at which other vessels pass, is

widely used, and its interpretation is unambiguous.

Due to the difficulty in determining the safety pa-

rameter indicating the width of the domain designa-

tion was proposed based on the analytical relation-

ship between the length and width of the domain.

This relationship can be derived on the basis of ship

domain analytical descriptions proposed, inter alia,

in (Coldwell 1983, Zhao et al. 1993, Smierzchalski

& Weintrit 1999, Pietrzykowski 2008, Pietrzykow-

ski & Uriasz 2009, Wang et al. 2009):

= f (D

) (4)

The simplest figure describing the domain of the

ship on the basis of the parameters (D

, D

) is a rec-

tangle. Taking into account the results of statistical

research on the shape of the domain, the domain was

proposed in the shape of an ellipse inscribed in a

rectangle with sides (D

, D

The parameter BCR- bow crossing range can be

an alternative to the CPA safety parameter, used for

describing the length and, consequently, the width of

the domain.

ECDIS system gives definitely a lot more oppor-

tunities for determining the domain of the third di-

mension - depth D

(three-dimensional domain).

The parameter defining the third dimension of the

domain can be safety contour or properly set safety

depth. It seems to be necessary to use safety depth,

which results from a broader range of hazards ana-

lyzed by the system for that parameter.

Then a three-dimensional domain is described as

a solid with two bases in parallel planes. The upper

base is an ellipse (two-dimensional domain). The

bottom base is a circle defined by the radius D

navigational danger ring. The circle origin is an or-

thographic projection of the ellipse origin. The side

surface of a geometrical solid is a section of the

plane connecting the two bases with the smallest

surface area (Fig. 2).

Fig. 2 Three-dimensional domain

When the domain function is implemented in the

ECDIS, the domain parameters (D

, D

)

will be generated automatically as a default with the

possibility of correction by the navigator (like other

safety parameters).

5 CONCLUSIONS

Based on analysis of alarms and indications of EC-

DIS system and safety parameters defined by the

navigator, the group of basic parameters necessary

for the safe sea passage was proposed particularly

for use in restricted areas. These parameters will be

available after activating the "Basic Safety Parame-

ters Settings" in an additional window. This allows

the navigator to set alarms, activate them and define

the safety parameters necessary to ensure safe sea

passage of the ship equipped with ECDIS. When the

solutions herein proposed are implemented by man-

ufacturers and positively verified by navigators in

practice, it will be recommendable to consider op-

tions for revising the performance standards for

ECDIS systems.

Due to the limited capacity of the CPA parameter

to be used in the safety assessment when navigating

in restricted areas, these authors considered the pos-

sibility of defining the ship domain as a safety crite-

rion in the ECDIS system. The definition of two-

and three-dimensional ship domain based on the

safety parameters defined in the ECDIS system is

proposed.

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