483
1 INTRODUCTION
ECDIS is a complex, safety‐relevant, software‐based
system with multiple options for display and
integration.Theprimary function oftheECDIS isto
contributetosafenavigation.
ECDIS should always have at least the same
reliabilityandavailabilityofpresentationasthepaper
chart published by government
authorized
hydrographic offices. In such case ECDIS units on
board are required to comply with one of two
performance standards (either IMO resolution
A.817(19), as amended or resolution MSC.232(82)),
dependingonthedateoftheirinstallation.
Essentially,whereanECDISisbeingusedtomeet
thechartcarriagerequirementsof
SOLAS(regulation
V/18,V/19,V/27)itmustbealsotype‐approved,use
up‐to‐date electronic nautical charts (ENC), be
maintained so as to be compatible with the latest
applicable IHO standards and have adequate,
independentback‐uparrangementsinplacetoensure
safenavigationincaseofECDISfailure.
In
addition, all ENCs and RNCs must be of the
latestavailableeditionandbekeptuptodateusing
boththeelectronicchartupdates(ENC)andthelatest
availablenoticestomariners.TheECDIS,eitherwith
an ENC on display or operating in RCDS mode,
shouldbecapableofdisplaying
allchartinformation
necessaryforsafeandefficientnavigationoriginated
by, and distributed on the authority of government
authorizedhydrographicoffices.
ECDIS Limitations, Data Reliability, Alarm Management
and Safety Settings Recommended for Passage
Planning and Route Monitoring on VLCC Tankers
G.Rutkowski
TeekayLearningandDevelopmentCenter,Manila,Philippines
TeekayShipping,Norway
ABSTRACT: The purpose and scope of this paper is to describe the factors to consider when determining
ElectronicChartDisplayandInformationSystem(ECDIS)limitation,datareliability,alarmmanagementand
ship’ssafetyparametersettings.Fortheoptimumsituationalawareness,navigatorsmust
alwaysrecognizethe
levelofdisplayforobjectspresentedwhenusingECDIS.Thevaluesforthesafetydepthandsafetycontour
must be understood and entered to achieve a sensible and considered meaning and alarm settings. The
navigatorsmustrememberthatthedisplayofunderwaterobstructionsorisolateddangersymbols
canchange
accordingtothesettingsofthissafetycontourwhichalsomarksthedivisionbetweennavigable(safe)andnon‐
navigable(unsafe)water.Impropermanagementofthesystemmayresultintheanti‐groundingalarmsand
otherindicationsfailingtoactivateasrequiredforthesafeconductofthenavigation.Consequently,
itcould
giveafalseimpressionofsafewatersaroundthevesselwheresome dangers maynot be showndueto the
limitations imposed by original chart scale. This paper recognizes the limitations of ECDIS display, the
significanceofappropriatesafetysettingsaswellasthealarmmanagementrecommendedfor
passageplanning
&routemonitoringonVLCCtankers.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 12
Number 3
September 2018
DOI:10.12716/1001.12.03.06
484
ECDIS software should be kept up to date such
that it is capable of displaying up‐to‐date electronic
charts correctly according to the latest version of
IHOʹs chart content and display standards in
accordance with IMO Safety of Navigation
SN.1/Circ.266.
ECDISsystem,untilusedaccuratelyandproperly,
always
can be recognized as a valuable tool in
assistingnavigatorsandallowingthemmoretimeto
maintain a proper lookout and more detailed
situationalawareness.Unfortunately,ithasbeenalso
noted (e.g. Weintrit (2009, 2018), IMO Resolution
MSC.Circ.1391(2010)),that manynavigatorshavea
tendencyto puttoo much
relianceon ECDIS with a
potential to threatenthe safety of navigation, which
may contribute to accidents rather than preventing
them.
Improper management of the system may also
result in the anti‐grounding alarms and other
indicationsfailingtoactivateasrequiredforthesafe
conductofthenavigation.
2 ECDIS
DATARELIABILITY
Navigating a ship with ECDIS is fundamentally
different from navigating with paper charts. Unlike
paperchartswheresourcedatadiagramsaremostly
provided,ElectronicNavigationCharts(ENC)donot
provide this information. Instead they provide the
navigator with a facility to examine reliability and
qualityofsourcedata
presentedonchartsbymeans
ofCategoryZoneofConfidence(CATZOC).
Figure1.ExampleofSourceDataDiagramfromBA1697(on
theleft)andexampleofCATZOCdisplayedonanENC(on
theright).
Figure2.CategorizationofCATZOC’s.Source:RegulationoftheIHOforInternationalchartsandchartsspecificationofthe
IHO’swhitepaper.,Availableat:https://www.admiralty.co.uk
485
Figure3.MutualrelationshipbetweenSafetyDepth,SafetyContour,ShallowContourandDeepContour.
Figure4. Display of Safety Depth, Safety Contour, Shallow Contour, Deep Contour, Safe Hazards and Isolated Danger
presentedonENCmapsinECDISsystems.
This gives an estimate of the reliability of data
related to five quality categories for assessed data
(ZOC A1, A2, B, C and D) and a sixth category for
data which has not yet been assessed. When
displayed by the ECDIS, CATZOCs are
distinguishable by the shape of the symbol and
the
numberofasteriskscontainedwithinit.
The categorization of hydrographicdata isbased
on three factors: position accuracy, depth accuracy
andseafloorcoverageforeachZOC tohelpmanage
the level of risk when navigating in a particular
geographicarea.
ZOCcategoriesreflectachartingstandardandnot
just
a hydrographic survey standard. Depth and
position accuracies specified for each ZOC category
refertotheerrorsofthefinaldepictedsoundingsand
include not only survey errors but also other errors
introducedinthechartproductionprocess.
Positionaccuracyofdepictedsoundingsat95%Cl
(2,45sigma)withrespectto
thegivendatum.
Depth accuracy of depicted soundings at 95% Cl
(2,00 sigma) with respect to the given depth (d) in
metersatthecriticaldepth.
Position and depth accuracy need not be
rigorouslycomputedforZOC’sB,CandDbutmay
beestimatedbasedontypeofequipment,
calibrating
regime,historicalaccuracy.
When using ENC’s with low data accuracy
navigator(OOW) hasto be more vigilant, and carry
outrepeatedcrosscheckswithinformationavailable
fromothernavigationalaids.
WheneverpossibletheaccuracyoftheENC’stobe
crossedcheckedwithinformationavailablefromlocal
agents, Pilots or local
authorities. CATZOC features
mustbeconsideredwhiledeterminingvesselssafety
contoursettings.CATZOCsareonlyvisiblewhenthe
user has selected the appropriate ENC layer for
display.
3 ECDISSAFETYSETTINGS
Appropriate safety settings are of paramount
importance for ECDIS display and safety of
navigation.TheOOWmustunderstandthe
valuesfor
thesafetydepth,safetycontourandsetthemproperly
to achieve a sensible and well thought‐out
implication.
In addition, the oncoming navigator during
changeof watch shall also verify the ECDIS display
settings, alarms settings and safety parameters
settingsbeforetakingoverthewatch.
Chart objects and
information available in SENC
fordisplayaresub‐dividedintothreecategories:Base
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Display,StandardDisplayandAllOtherInformation
(IMO Resolution A.817(19) and/or IMO Resolution
MSC.232(82)).
TheBaseDisplayisthebasicdisplayprovidedby
theSENCandisrequiredforallcharts.Itisthebasic
datathatcannotbealteredbytheoperator.
The Display Base contains information on
coastlines,
safetycontours, dangerindications,traffic
routing,scale,range,orientationanddisplaymode,as
wellasunitsofdepthandheight.TheDisplayBaseis
notintendedtoprovideenoughinformationforsafe
navigationjustbyitself.
The Standard Display, which is also a pre‐
arrangedchartdisplay,butwhichcan
bemodifiedby
theoperator,andwhichisautomaticallyshownwhen
theECDISisfirstswitchedon.Itcontainsthedisplay
base plus boundaries of channels etc., conspicuous
features, restricted areas, chart scale boundaries and
cautionarynotes.
The operator can modify the amount of
information displayed for the purposes of route
planning and navigationalmonitoring. The operator
decideswhatlevelofinformationisdisplayedduring
any particular situation or task. However, when
working with these other levels of information
display, an operator must immediately be able to
returntothestandarddisplaywithjustonesinglekey
strokeoractionof
thecontrols.
The standard display, as defined in the ECDIS
Performance Standards (IMO Resolution A.817(19)
and/or IMO Resolution MSC.232(82)), does not
necessarilydisplayallthechartobjectsnecessaryfor
safe navigation under all circumstances, e.g. spot
soundingsorunderwaterobstructions.
Theseandotherobjectsareall listed or classified
as ‘All
Other Information’ display. Different
manufacturers provide different facilities for
managing the display of chart objects and chart
information.Controlof individual groupsof objects,
e.g. spot soundings, tidal diamonds, place names,
may vary according to each ECDIS manufacturer.
Selectionofcertainlayersofinformationorobjectsfor
display becomes more
obvious with experience but
until then navigators will need to understand the
layer selection requirements for an efficient
navigationaldisplay.Marinersneedalsotoremember
that displaying everything, without seamanlike
consideration,shouldnotbeanoption.
Withsomesystems,itispossibletorunacomplete
safetycheckforanyhazards
alongtheplannedroute
atanytimeduringtherouteplanningprocessandon
completion of planning. However, this functionality
varies among the different makes. Some ECDIS
appear only to undertake route check functions on
larger scale ENCs and therefore alarms might not
activate.Thismaynotbealsoclearly
indicatedonthe
ECDISdisplayscreen.
Mariners should always undertake careful visual
inspectionof theentire planned route using the ‘All
Other’ display mode to confirm that it, and any
deviationsfromit,isclearofdangers.Watchkeeping
Officers should verify that all compulsory
information (base & standard) are selected.
Masters
arerequired to prescribe minimum display category
requirements on the ECDIS for each stage of the
voyage. Usually there is also recommendation (e.g.
basedonTeekayNavigationalHandbook(2017))that
thefollowinginformationareincludedinusercharts
during passage planning stage: watch condition,
positionfixinterval,primaryand
secondaryposition
fixmethods,parallelindexing,maximumspeedbased
on minimum required UKC, echo sounder/printer
activation,abortline/pointofno‐return,NoGoAreas
(anti grounding alarm enable),
contingency/emergency anchorages, VTS reporting
points, special zones (MARPOL, ECA, etc.), any
master’s remarks (any orders, comments, etc.), all
importantnotices/remarks(1hournotice
toER,ERto
be manned, etc.). In addition, ‘chart auto load’ and
‘chartautoscale’aretobeonatallthetimeswhenin
navigation. If two ECDIS are installed, one ECDIS
shouldalwaysbesettothebestscale(1:1).
SCAMIN is an optional attribute by the
chart
producer (defined by IHO S57) that can be used to
label ENC chart features to be suppressed above a
certaindisplayscale.Themainfunction ofSCAMIN
istode‐clutterthechartdisplay,enablingtheuserto
focusonthemostusefulnavigationalinformationfor
the display scale in
use. SCAMIN may affect the
display as it removes certain information from the
displayifbestscalechartisnotbeingusedi.e.safety
criticalinformationmayberemovedfromthedisplay.
A buoy that has the IENC Encoding Guide’s
recommendedSCAMINsettingof10000willonlybe
shownon
the display if the selected display scale is
greaterthan1:10000(Largerscale).
The system auto‐filter means that unless
navigatingonthebestscalechart,OOWwillnotsee
all the information available for display. Therefore,
when zooming out the system will automatically
deselect certain features from display such
as
soundings,lights and topographical detail. The only
way to ensure that the display is not affected by
SCAMIN is to always ensure that the chart is being
used on the best scale. Navigators should always
checkthepassageplansat‘compilationscale’before
useandduringroutemonitoring.
Compilation
scaleisthescaleoftheENCatwhich
the chart data was compiled based on the nature of
the source data. It’s the scale at which the chart
information meets the IHO requirements for chart
accuracy.
Navigators must exercise extreme caution when
using the scale or zoom facility of the
electronic
charts.Itispossibletozoom‐intoascalelargerthan
thatusedinthecompilationofthedatawhichcould
create a false impression about the reliability of the
charted information. Consequently, it could give a
falseimpressionofsafewatersaroundthevessel.
Also,somefeatures
maybenotdisplayedbecause
of the SCAMIN (Scale Minimum) attribute of ENC
objects.Zoomin/outfunctionshouldonlybeusedfor
shortperiodsoftime.IfpossibleSCAMINsettingsto
bekept‘off’duringthepassageplanningstage.
Safety depth (SD) is a value that serves to detect
depthsthat
areadangertonavigation.Adepthequal
toorlessthanthesafetydepthishighlightedonthe
chart in bold type when the display of the spot
sounding is turned on. This alertsthe userto know
487
thedepthsthatareinsufficientforthevesseltosafely
pass over. Additionally, if any extra allowance of
depth is required due to local port or berth
requirements, same should be included in the
calculation of the safety depth. Safety Depth is not
required to trigger any alarm or indication
as per
ECDISperformancestandards.
Safetycontour(SC)valueiscalculatedconsidering
Safety Depth and allowing for CATZOC; (Safety
Contour=SafetyDepth+CATZOC).Inoceanwaters
ifthe calculatedsafety contour value is greater than
50m,thenthevaluecanbesetat50m.
ECDIS selects and highlights
default safety
contour, which is equal to or deeper than the safety
contourvalueselectedbytheuser.SafetyContouron
ENCdisplaywilldefaulttothenextdeepercontourif
thedepthcontourofthesetvalueisnotavailablein
thedisplayedENCsourcedata,e.g.ifSafetyContour
setting=minimumdepthrequired=9.0m,thesafety
contour selected on most ENCs, where the original
dataismetricwillbe10m(andnot9.0m)orif10m
contourisnotavailableinSENC,then15mor20m
whicheverhigheristhenextavailable
inSENCbase.
ItshallbealsonotedthatonENCswheretheoriginal
source data was imperial units (feet/ fathom) the
depth contours on ENC may be in figures such as
9.1m,18.2m.
The safety contour marks the division between
navigable(safe)andnon‐navigable(unsafe)water.If
the
navigator does not specify a safety contour, this
willdefaultto30mor50mvaluedependingontype
and/ormodelofECDIS.Thecontoursmayalsodiffer
between electronic charts produced by different
hydrographic offices. During route planning, an
indicationwillbemadeiftherouteisplannedtocross
theship’ssafetycontour.
At the time of route monitoring, ECDIS should
give an alarm if, within a specified time set by the
navigator, own ship is likely to cross the safety
contour.
Thedivisionbetween‘safe’navigableand‘unsafe’
non‐navigablewaterishighlightedbychartcoloring,
withbluecolor
usedtoindicateunsafeareaandwhite
orgreyforsafearea.Theunsafeareamaybefurther
defined with the selection of a shallow contour,
showingdarkblueintheshallowwaterandlightblue
between the shallow water and the safety contour.
Theshallowcontourshouldbeused
tohighlightthe
gradientoftheseabedadjacenttothesafetycontour
andthedeepcontourtohighlightthedepthofwater
inwhichownshipmayexperiencesquat.
Using ECDIS the navigator must also remember
that displayed underwater obstruction or isolated
dangersymbolscanchangeaccordingtothesettings
of
the safety contour. Furthermore, the safe water
mayalsobesub‐dividedwiththeselectionofadeep
contour, in which case the area between the safe
contourandthedeepcontourwillbecoloredgrey.
However,ithasbeenalsoacknowledgedthatnot
allECDISmanufacturersprovideseparatecontrols
for
safety contour and safety depth value, some have a
common or a linked control. Some flexibility of the
systemislostwhenthereisonlyonecommoncontrol
for‘safetydepth’forboth the‘safetydepth’ and the
‘safety contour’. In such cases, author recommends
thatthe safety contour value
should be used for the
safetydepthonECDISwithsuchfeature.
Where the manufacturer provides for separate
controlsforsafetydepthandsafetycontour,theuser
cansubstantiallyincreasetheirsituationalawareness
bychoosingthe valuesasindicatedin the following
formulas:
SD=T
max+RUKC+Rsquat+Rd‐Htide (1)
SC=SD+CATZOC (2)
where:SD=safetydepth[m];SC=safetycontour[m];
T
max= ship’s draught [m]; Rsquat= estimated squat [m];
R
UKC= required Under Keel Clearance [m]; Rd=
dynamicreservecausedbyship’soscillationonwave
+ rolling and pitching [m]; H
tide= tide height above
chart datum [m]; CATZOC= Category of Zone of
Confidence[m].
Example 1. Calculations for CATZOC(A1): Ship’s
draftT
max=10m,requiredUnderKeelClearanceRUKC=
2.0m(UKCPolicyforopencostalwater’s=20%static
draft T
max), estimated maximum squat Rsquat= 0.8m,
depthofwater(d)=30m,depthaccuracyinCATZOC
AreaA1=0.5m+1%depth=0.8m.Tideheightabove
chart datum H
tide=0.8m, dynamic reserve caused by
ship’soscillationon wave R
d=1.0m(in practice, itis
usuallytakenas2/3ofthewaveheight).Thenusing
formula(1)and(2)wewillhave:
SafetyDepth(SD)=10.0+2.0+0.8+1.0‐0.8=13.0m,
SafetyContour(SC)=13.0+(0.5+0.01∙30.0)=13.8m.
However,SafetyContouronENCdisplay(SC
SENC)
will default to the next deeper contour if the depth
contouroftheinputvalue(13.8m)isnotavailablein
thedisplayedENCsourcedata(SENC).
In our example where (SC= 13.8 m) the safety
contour selected on most ENCs where the original
dataismetricwillbe(
SCSENC)=15m(andnot13.8m)
orif15mcontourisnotavailableinSENC,then20m
or25mwhicheverhigheristhenextavailable.
ItshallbenotedthatonENCswhere theoriginal
source data was imperial units (feet/fathom) the
depthcontours onENC maybe
also selected as e.g.
18.2m.
Example2:CalculationsforCATZOC(D/U):Ship’s
draftT
max=10m,requiredUnderKeelClearanceRUKC=
2.0m,estimatedmaximumsquatR
squat=0.8m,depth
ofwater(d)=30m,depthaccuracyinCATZOC(D)=
(2.0m±5%depth)∙1.1=3.85m,tideheightabovechart
datumH
tide=0.8m,dynamicreservecausedbyship’s
oscillation on wave R
d= 1.0 m. In such case using
formula(1)and(2)wewillhave:
SafetyDepth(SD)=10.0+2.0+0.8+1.0‐0.8=13.0m,
SafetyContour(SC)=13+(2+0.05∙30)∙1.1=16.85m.
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Safety Contour on ENC display (SC
SENC) will
defaulttothenextdeepercontouriftheinputvalue
(SC=16.85 m) is notavailablein thedisplayed ENC
sourcedata.
Inourexamplethesafetycontourselectedonmost
ENCs where the original data is metric will be
(SC
SENC)=20m(andnot16.85m)orif20mcontouris
notavailableinSENC,then25mor30mwhichever
higheristhenextavailable.
Since allowance for CATZOC is considered in
SafetyContour,theremaybesituationswherevessel
havetocrossandnavigatewithinsafety
contourarea.
This will enable the audio & visual alarm. When
navigating within the safety contour limits, vessel
must mark all ‘No‐Go’ areas and navigate with
particularcaution.Thisistheonlysafewatersetting
thatgivesalarm/advancewarning to theuseras per
ECDIS performance standards (IMO Resolution
A.817(19)and/orIMOResolutionMSC.232(82)).
ItisimportanttonotethatSafetyDepthandSafety
Contour settings are dynamic and not fixed for the
entireplannedroute.Itwillhavetobemonitoredand
changedbythe userasrequiredfor eachleg/section
of the voyage depending on factors like UKC
requirements,speedandavailabledepthandwidthof
water.
Shallowcontoursettingisgenerallyselectedequal
tothemaximumdynamicdraftofthevessel,(Shallow
Contour≈T
max). These indicates the depth below
whichvesselwillrunaground.In certainports with
hightidalranges,thevesselsarelikelytoencountera
scenariowhereintheShallowContourvalueswillbe
greater than Safety Contour and/or Safety Depth
values. For safety reasons, this setting (Shallow
Contour greater than Safety
Contour) are not
accepted by ECDIS’. In such scenarios, the Shallow
contour value should be set equal to Safety Depth
values.
Deepcontourshouldbesetattwicethedraftofthe
vessel,(DeepContour≥2∙T
max).Thisismeanttomake
the user aware that below this value shallow water
effects shall get pronounced. The area between the
deepcontourandsafetycontourisgenerallyshaded
in light grey color and deep waters are marked in
white color. However, it must be also noted that
alarms
and/or indication are not associated with
shallowanddeepcontours.
Isolated Dangers there are underwater
abstractions (shallows, rocks, wrecks, reef, offshore
loading installation etc.) with a depth above them
smallerorequalvaluesofthedeclaredsafety contour.
InECDIS,isolatedhazardscanbepresentedonthe
screeninthe
formofaredborderwithatransparent
X in the center, but only if the user activates the
appropriatelayerofadditionalinformationaboutthe
navigational threats (Safe Hazards ON, Danger
symbolON)–seefigure4.
4 ECDISALARMMANAGEMENT
ECDIS provides a large number alarms and
indications.An
alarminthiscontextmeansanalarm
oralarmsystemwhichannouncesbyaudiblemeans,
or audible and visual means, a condition requiring
attention. An indicator is a visual indication giving
information about the condition of a system or
equipment. From navigators ‘perspective, ECDIS
alarm management is very critical as
it could vary
from manufacturer to manufacturer. Some
manufacturers allow the mandatory alarms to be
disabledandsomeevenallowchoiceofchartscalefor
alarmchecking.
In addition, the level of control over alarms may
vary from being very detailed control to minimal
control. The vessel’s voyage specific parameters
including
alarms shall be programmed during the
appraisal stage of passage planning and must be
approvedbytheMaster.
When ECDIS is in use for navigation, the
navigatingofficerOOWmustensurethatappropriate
alarms and/or indications (as mentioned) below are
availableandactiveonECDIS.Failuretodosomay
lead to missing out significant navigational
information and may lead to rendering the type
approvalcertificateofthesysteminvalid.
All alarms on navigational hazards, information
input malfunction, information conflict by way of
visual and audible alarms requires an immediate
response from operator. All ECDIS alarms and
indications shall be acknowledged
and investigated.
The OOW shall not rely solely on automated
monitoring alarms generated by the ECDIS.
Reconciliationbetweentheviewfromthebridgeand
the vessel position with respect to charted features
shallbemaintainedincludingacheckthatthesensors
areprovidinganaccuratefixofthevesselposition.
In normal circumstances ECDIS automatically
provide warnings if it malfunctions or when
developing a fault and/or if it has detected an
approachingnavigationproblem.
Therearealsothreecategoriesofsituationswhich
can trigger warnings. Navigational hazards, alerting
theoperatortoapotentialnavigationalhazardduring
route planning or monitoring, such
as the ship
crossingasafetycontour.
Information input malfunction, indicating the
breakdown of a sensor, such as the failure of the
GNSS or of the ECDIS itself and in addition
‘information conflict’, indicating a datum or chart
miss‐match, such as a changed horizontal geodetic
datumorawrong
scalesettingwhichcouldcausea
miscalculationofdistances.
The five mandatory alarms (as per IMO ECDIS
Performance standards) are: crossing safety contour,
deviation from route, positioning system failure,
approach to critical point and different geodetic
datum.
Alarm or Indication must be activated when
malfunction of ECDIS and/or when vessel
approachingtoareawithspecialconditions.
Itmustbealsonoted,that appropriateindication
should be available on ECDIS screen in case of the
following circumstances: default safety contour,
information over scale, large scale ENC available,
different reference system, no ENC available,
customized display, route planning across safety
contour,routeplanning
acrossspecifiedarea,crossing
489
adangerinroutemonitoringmodeand/orincaseof
systemtestfailure.
WhenECDISisinusefornavigationusingraster
charts (RCDS), to comply with the performance
standards, the navigating officer should ensure that
the following alarms are available and active:
deviation from route, approach to mariner entered
feature (e.g. area, line), positioning system failure,
approach to critical point. Alarm and/or indication
shouldbeactivatedfordifferentgeodeticdatumand
malfunctionofRCDSmode.
In addition, the following indication should be
available on ECDIS screen: ECDIS operating in the
rastermode,largescaleinformationavailableorover‐
scale
andlargescaleRNCavailablefortheareaofthe
vessel. Failure to do so may lead to missing out
significantnavigationalinformationandmayleadto
renderingthetypeapprovalcertificateofthesystem
invalid.
ECDIS shall also detectand provide an alarm or
indication when entering areas in
which special
condition exists, such as: traffic separation zone,
inshore traffic zone, restricted area, caution area,
offshore production area, areas to be avoided, user
defined areas to be avoided, military practice area,
seaplane landing area, submarine transit lane,
anchorage area, marine farm, aquaculture,
ParticularlySensitiveSeaArea(PSSA)etc.
However, it
must be also noted that too many
alarmscanleadtoan‘AlarmOverload’situation.
Ontheotherhand,toolesscanleadtofalsesense
of security. Effectively stepping up and stepping
downthenumberofalarms/indicationsatthevarious
stagesofthevoyageisimportantforefficientECDIS
assistednavigation.
The ECDIS specific information regarding when
the system detects and provide an alarm should be
readily available near the ECDIS unit. Master shall
adjust the alarm setting parameters throughout the
voyage to ensure that they are optimized for the
prevailingcircumstancesandconditions.
However, he shall also ensure that
at any given
time during the passage, the OOW areaware of the
settings. The system may give alarms by way of
visual,audibleandvisual/audible.
Otherthanthemandatoryalarms,theECDISmay
havethefollowingalarms:
Anchor watch alarm/indication to indicate when
thevesseldriftsoutfrom
thesetlimitsofswinging
circleatanchorage.
Wheelover positions alarm/indicationto indicate
whenreachingthosepoints.
CPA/ TCPA alarm/indication for targets input
provided by ARPA and AIS (e.g. suggested
guidance for VLCC tankers includes combined
CPA and TCPA of 1.0 NM and 12 mins and/or
morethan
4opposingtargetsoneithersidewithin
3NMradius).
The guard zone (also known as Safety Frame)
provides the user with an advance warning of
dangers/cautions.Theusersetsthedimensionsofthis
guard zone which must be altered according to the
prevailing circumstances to prevent unnecessary
alarms or
to give adequate warning.The navigators
needtorememberthatnotalldangersareenclosedby
acontourandguardzoneremainsactiveevenifitis
notselectedtodisplayonthescreen.
In order for the alarm system to be properly
effective(whentherouteisbeingmonitored)the
own
ship’s guard zone must be set in a seamanlike
manner, i.e. with a sensible time or range warning
depending on proximity to hazards and planned
speed etc. It is also recommended to set the guard
zoneaslargeaspossibleasthecircumstancesallow.
Safety Frame / Watch Vector
are also known as
‘AntiGroundingCone’or‘LookAheadSetting’.
The setting is based on stopping distance and
turning circle criteria of the vessel. Without proper
setting of this feature, early warning of most of the
navigationalhazardsinandaroundthevessel’sroute
shallnotbeavailable.However,this
featuredoesnot
providealarmsforARPAandAIStargets.Thesafety
frame/watchvectoristobesetupdependingonthe
Master’s discretion and recommended values for
Safety Frame/ Watch Vector/ Look Ahead Settings
andforVLCCtankersareusuallyasfollows:
OpenSea:Ahead:15min,width:
1.0NMoneither
side.
Coastal Waters: Ahead: 10 min, width: at least
equaltothetacticaldiameterofthevesselinNM
oneitherside.
Harbor/ConfinedWater:5min,atleast0.25NMor
asmuchaspossible.
Thecross‐tracklimits(XTL)settingmadeforeach
leg
during the planning stage shall be reviewed
taking into account the available sea room and
Master’s discretion. Recommended settings for XTL
valuesforVLCCtankersareasfollows:
Open Sea: Minimum XTL: 1.0 NM either side of
thecourse.
Coastalwater:MinimumXTL:0.5NMeitherside
of
thecourse.
Harbor/ConfinedWaters:MinimumXTL:0.25NM
oneithersideorasmuchaspossible.
5 CONCLUSION
Navigators should always cross check ECDIS
information with the other sources and most
importantly,avisuallookout,as‘humaneyesarethe
mostvaluabletoolatamariner’sdisposal’.
When monitoring a
route, the prudent navigator
mustalwaysmaintainacheckontheintegrityofthe
displayed position of own ship. When thesource of
thedisplayedpositionistheownshipsGNSS,thereis
alwaysa possibilitythat the position displayed may
notcoincidewiththeship’sactualpositioninrelation
tothechartorthechartedhazards.
A check may be made quite simply by utilizing
one or any of the following: manual position fixing
(visual/Radar), look out of the window, comparison
of ARPA overlay of a fixed mark with the charted
position, comparison of a radar overlay with
conspicuous land
or fixed targets, observation of a
parallel index on the radar display to monitor
comparisonwithplannedtrack,monitoringthedepth
490
shownbyechosounderwhereappropriate,checking
thetrackhistoryetc.
Navigators must also take into consideration the
ECDIS limitation when using the scale or zoom
facilityoftheelectroniccharts.Itispossibletozoom‐
intoascalelargerthanthatusedinthecompilation
of the data
which could create a false impression
aboutthereliabilityofthechartedinformation.
Consequently, it could give a false impression of
safe waters around the vessel where some dangers
maynotbeshownduetothelimitationsimposedby
originalchartscale.
ItisessentialthattheMasters,navigatingofficers,
and ship‐owners are aware of the benefits of
managingthechartdisplay,safetysettings,andalarm
systemofECDIS.
Toomanyalarmscanleadtoan‘AlarmOverload’
situationand on the other hand too less can lead to
falsesenseofsecurity.
Effectively stepping up and stepping down the
numberofalarms/indicationsatthevariousstagesof
the voyage is important for efficient ECDIS assisted
navigation.
Thevaluesforthesafetydepthandsafetycontour
mustbeunderstoodandenteredtoachieveasensible
andconsideredmeaning.
Thenavigatorsmustrememberthatthedisplayof
underwater obstructions or isolated
danger symbols
can change according to the settings of this safety
contour which also marks the division between
navigable(safe)andnon‐navigable(unsafe)water.
Additionally, the shallow contour could be
utilized to indicate the gradient of the seabed
(adjacent to a channel) and the deep contour to
indicate the depth
of water in which own ship may
experience squat and interaction. Consequently,
impropermanagementofthesystemmayresultinthe
anti‐groundingalarmsandotherindicationsfailingto
activateasrequiredforsafeconductofthenavigation.
REFERENCES
IHO’s ‘Regulation of the IHO for International charts and
chartsspecificationoftheIHO’swhitepaper.’Zonesof
Confidencetakenfrom:ttps://www.admiralty.co.uk
IMO Resolution A.817(19): Performance Standards for Electronic
Chart Display and Information Systems (ECDIS). Available
at: http://www.ecdis-info.com.
IMO Resolution MSC.1/Circ.1503/Rev.1, ECDIS – New
guidanceforgoodpractice(2017‐06‐16)
IMOResolutionMSC.232(82)adoptedon5December2006:
Adoption of The Revised Performance Standards
for
ElectronicChartDisplayandInformationSystems(ECDIS).
Availableat:http://www.imo.org.
IMO Resolution MSC. Circ.1391, Operating Anomalies
IdentifiedwithinECDIS(2010‐12‐07).
IMOSafetyofNavigationSN.Circ.266Rev1.Maintenance
ofECDIS(22Oct2007).
Teekay internal document No.: SP1915 v.2, Navigational
Handbook,(2017‐02‐28).
Teekay internal
document No.: RF1112 v.3, ECDIS‐
CategoryZoneofConfidence(CATZOC).
Teekay internal document No.: RF1113 v.5, ECDIS Navigation
(General, Technical & Safety Information), March 2018.
Weintrit, A. 2009, The Electronic Chart Display and
Information System (ECDIS). An Operational
Handbook. A Balkema Book. CRC Press, Taylor &
FrancisGroup.ISBN:9780415482462.
Weintrit A.: Reliability of Navigational Charts and
ConfidenceintheBathymetricDataPresented.Scientific
JournalsoftheMaritimeUniversityofSzczecin,No.54
(126),pp.84–92,2018.
WeintritA.:AccuracyofBathymetricDataintheElectronic
NavigationalCharts.ScientificJournalsoftheMaritime
UniversityofSzczecin,No.55(127),pp.60‐69,2018
.
