317
1 INTRODUCTION
1
st
of July 2015 will be half of the period of
mandatoryElectronicChartDisplayandInformation
System (ECDIS) implementation. This sixyear
implementationperiodappearsasalongtermlook
ahead;however,takingtheenormouschangeandthe
need to adapt in consideration, it requires certain
issues to be solved properly and, ab
ove all, timely.
Afterthe implementation ending date, therewill be
increasinglylesstimeforsolvingorreviewingarising
problems.Itespeciallyreferstopositioning,whichis
by mandatory means incorporated in the ECDIS
system,acting as anintegratedpart of it. Here,itis
not about a traditional classification of ma
ritime
navigation in general and coastal navigation, but
about a fact that reliable positioning and its
redundancyrepresentsfundamentalsafetyfactoron
board navigating vessels. Positioning methods
dependonthenatureofthetypeofnavigationwhich
takes place as well as available positioning means.
Global Navigation Satellite Systems (GNSSs) are
nowadays used as prima
ry positioning sources in
ECDIS.Theyprovidemostreliableandmostaccurate
positions among others; however they are not
immune to errors and failures. The safety of
navigationrequiresausageofsecondarypositioning
sourceinECDISsystemasatrustyredundancyback
up in the case of potentia
l primary positioning
failure.Moreover,thereappearsastrongneedforits
Navigation with ECDIS: Choosing the Proper
Secondary Positioning Source
D.Brčić,S.Kos&S.Žuškin
FacultyofMaritimeStudies,UniversityofRijeka,Rijeka,Croatia
ABSTRACT: The completion of ECDIS mandatory implementation period onboard SOLAS vessels requires
certainoperational,functionalandeducationalgapingholestobesolved.Itespeciallyreferstopositioningand
itsredundancy,whichrepresentsfundamentalsafetyfactoronboardnavigatingvessels.Theproposedpa
per
deals with primary and secondary positioning used in ECDIS system. Standard positioning methods are
described, discussing possibilities of obtained positions’ automatic and manual implementation in ECDIS,
besidedefaultmethods.Withtheaimofemphasizingtheneedandimportanceofusingsecondarypositioning
sourceinECDIS,positioningissuefromthestandpointofendusers waselaborated, representingapra
ctical
feedback of elaborated topic. The survey was conducted in the form of international questionnaire placed
among OOWs, ranging from apprentice officers to captains. The result answers and discussion regarding
(non)usageofsecondarypositioningsourcesinECDISwereanalysedandpresented.Answersandstatements
wereelab
oratedfocusingnotonlyinusageofthesecondarypositioningsysteminECDIS,butinnavigationin
general.Thestudyrevealedpotentialrisksarisingfromthelackofknowledgeandevennegligence.Thepaper
concludes with summary of findings related to discrepancies between theoretical background, good
seamanshippracticeandrealact
ionstakenbyOOWs.Furtherresearchactivitiesarepointedout,togetherwith
plannedpracticalactionsinraisingawarenessregardingnavigationwithECDIS.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 9
Number 3
September 2015
DOI:10.12716/1001.09.03.03
318
verification by comparing obtained positions with
other, independent methods and techniques. The
proposed paper deals with positioning in ECDIS
system and the usage of reliable secondary
positioningsource.Standardpositioningmethodsare
described along with their pros and cons, pointing
out the possibility of obtained positions’
implementation in ECDIS. Considering
common
navigationalpracticeandtheoreticalbackgroundfor
good seamanship, the positioning issue from the
standpointoftheendusers,i.e.navigationalofficers
was elaborated. During the period of 20132015 a
surveyintheformofinternationalquestionnairewas
placed among seafarers, ranging from apprentice
officers to captains. The questionnaire
contains
questions related to experience with ECDIS,
operation,personalopinionregardingjustificationof
ECDIS system as a primary navigation mean,
withdrawal of paper charts and other specific
problems with which OOWs, as skilled endusers,
are facing with. Questions and answers regarding
ECDISpositioning were elaborated. The results and
discussion regarding
(non) usage of secondary
positioning in ECDIS were presented andanalysed.
Answers and statements were elaborated focusing
not only in using the secondary positioning in
ECDIS, but onnavigation in general.In this way, a
practicalfeedbackwasobtained,identifyingpotential
risksarisingfrom sequence of events in operational
navigation. The main causal process here is
transitional period of ECDIS implementation. The
paper concludes with summary of findings and
points out further research activities and practical
actions needed, aiming at safer navigation and
raisingsituationalawareness.
2 POSITIONING
This chapter gives an insight into positioning
methodsusednowadaysonboard
merchantvessels.
A short overview of traditional methods is also
presented, in order to emphasize the flow and the
significanceoftransitionperiod.Itrefersnotonlyto
positioning, but development of navigation tools,
navigation conduction in general and its
repercussions.
2.1 Generalconsiderations
Positioningcanbeclassifiedinorder
ofwhichtypeof
navigation takes place: ocean going, coastal,
navigation in port approaches and restricted
waterways,andnavigation inportareasandinland
waterways (Bowditch 2002, IMO A 860(20) 1997,
IMO MSC 915(22) 2001, Brčić et al. 2014). The
navigation type determines (available and proper)
positioning methods, positioning frequency
and the
required redundancy level. The most distinct
difference appears between ocean and coastal
navigation.Inopenseanavigation,theofficerofthe
watch (OOW) cannot rely on landmarks and shore
stations which are providing lines of positions
(LOPs)relativetomarkedobjects(Nav2013).Coastal
navigation therefore provides number
of reference
objects from which LOPs are derived, but also
represents greater risk for navigation (waterways,
restrictedpassageroutes,shallowwaters…).Inopen
sea,satellitepositioningisthemostcommonmethod,
also often and regularly employed in other
navigationsegments.
2.2 Anshortoverviewofpositioning
Depending on the type
of positioning source and
method used, position can be absolute
(unambiguous) and relative (related to an object),
employingdifferentcoordinate systems. On the one
hand, traditional positioning methods developed
overtime in pace withtechnology and navigational
equipment. On the other hand, the sole positioning
methodsremainedthesame,but
thenavigationtools
changed.Thepositioningprocessremains thesame.
New navigation methods are developing, becoming
moreaccurate,butalsomoresusceptibleatthesame
time.
Visual observations are the first and yet most
reliablepositioningandsituationalconfirmation.On
theopenseatheyarereferringonothervesselsinthe
first place, however in coastal navigation they are
consideredasthefundamentalwayfornavigational
situation interpretation and situational awareness.
The observed, orienteering directions from objects
aretakingformofbearings,andthechangingrateof
objects size gives an perception of distance to the
object. It determines two fundamental
lines of
position the azimuth and the true distance (polar
coordinate system LOPs). These two positioning
toolsarenowadays usedin almost all methods and
navigational devices, becoming more refined with
navigationaldevelopment.
Figure1presentsatraditionalpositioningmethod
based on the moment of appearance or
disappearanceofthe
objectonthehorizon(Kosetal.
2010).Itseemsunlikelythatthismethodisstillused;
howeveritillustratesthehumaningenuityonetime
before, when visual observations were sufficient to
obtainareliableposition.
Figure1. Position determination based on the moment of
appearanceordisappearanceoftheobjectonthehorizon.
Thisrangingmethodisbasedonthecalculationof
thecurvatureoftheEarth,Earthradius (R) and the
usageofdirectionfinder,e.g.magneticcompass(Kos
etal.2010):
12 eo
ddd kh kh  (1)
319
where d = distance to objectin (NM); h
e = height of
the eye of the observer; h
o = height of the observed
object; and k = constant calculated from the Earthʹs
mean radius and distance conversion in nautical
miles,k=1.9274.
Sincetheseahorizonisgreaterthangeometric,it
canbe stated thatk = 2. Thisleads to final distance
determination(Koset
al.2010):

2
eo
dhh (2)
Although aged, described positioning method
providesthenavigatorwithazimuth(directionline)
and distance (circle), the same lines of position on
whichcontemporarycoastalnavigationrelieson.
One of the first and sustained positioning
methodsis DeadReckoning(DR).In thismethod,a
knownposition is advanced on the
basis of vessel’s
course and distance prevailed regarding vessel’s
speed.Thismethodcanbeemployedalways,under
condition that there is one known position, known
course and known speed of the vessel. DR method
developed from manual plotting on navigational
charts to sophisticated methods embedded in
navigational devices, by employing various
differential and other algorithms. It can provide
reasonable accuracy, however it becomes fairly
inaccurate over time (Nav 2013). An Estimated
Position (EP) can be viewed as DR upgrade, where
outereffectson vessel’scourse and speed are taken
intoconsideration(e.g.setanddriftandotherleeway
effects), providing corrected
Course Over Ground
(COG) and Speed Over Ground (SOG) (Nav 2013,
Bowditch2002).
Celestial navigation positioning methods are not
reliantonanyelectronicsystems,andthepositionin
dueaccuracy(1NM)canbeobtainedbyusingthe
sextant, compass and nautical almanacsolely. Lines
ofposition(azimuthanddistances
again)arederived
by known locations and movements of celestial
bodiesstars,planetswhichareactingasreference
objects. Astronomical positioning methods are still
valid check in open sea navigation. However, with
the rise of new technologies and realtime
positioning, there appears a possibility that these
methods
willslowlygointooblivion.Thenumberof
vessels where sextant is not anymore obliged
increases, distancing celestial navigation methods
fromthecommonusage.
Radar represents an enhanced eye of the
navigator, providing visibility in different parts of
the frequency spectrum. Vessel’s position can be
obtained in several ways. LOPs from
reference
objects can be derived thusmanually providing the
position.Inanautomatedway(EchoReference‐ER),
the reliable object in vessel’s vicinity can be used,
providingvessel’scontinuouspositionrelativetothe
object.Radarisautonomousdevice,meaningthat it
is not dependent on any other source except
electricity.
Even in the case of connected sources
failure (e.g. heading and speed sources) it can be
used with satisfying positional accuracy (e.g. in
RelativeMotionmodeandHeadUporiented).Radar
positioningisconfinedtocoastalnavigation,whilein
opensearemainsaprimarycollisionavoidancetool.
As for (and not
only) ocean navigation, satellite
positioning provides the navigator continuous
service of positioning, navigation and velocity
determination, as well as time standard service
provision (Parkinson & Spilker, Jr. 1996, ISGPS
2013). Among all GNSSs, the Global Positioning
System (GPS) is most used, fully operable system.
Satellitenavigation isembedded in
various systems
which are based on its services. In relevant
navigational equipment, such as Automatic
IdentificationSystem(AIS)andECDIS,GPSnotonly
provides its services, but acts as anintegrated part.
With the development of multifrequency satellite
receivers (either employing several dedicated
frequencies from one GNSS system, or employing
various GNSS system’s frequencies) and local and
global differential services, satellite positioning
services are reaching great levels of accuracy and
reliability; however they are, as any other system,
susceptible and vulnerable to effects of number of
externalcauses(Chapter5).
A number of supplementary positioning and
situationalmethodscanbe
usedinordertoobtaina
positionandinterpretnavigationalsituation.Someof
them can be used as direct positioning means (e.g.
InertialNavigationSystems,orhyperbolicnavigation
systems where available) while other are used as
complementary navigation tools (e.g. Echo
Sounders).
This short positioning overview was given in
order to
present the choices and possibilities OOW
canemployinordertoobtainaposition,butwhatis
more important, to provide the OOW with
supplementary positioning means in redundancy
terms. Emphasizing the need for secondary
positioning source, every position has to be double
checked or multi checked. Moreover, theoretical
knowledge
ofpositional erroranduncertainty areas
isessential.
3 ECDIS
ECDISsystemunitscanbedividedinhardwareand
softwarecomponents,uninterruptablepowersupply,
official/updated databases (electronic charts) and
required sensor ports formandatory and additional
navigation and aiding devices (IMO MSC 232(82)
2006, IMO A 817(19)1995). Thesedevices in
ECDIS
contextactasasensors,and they are not treated as
standalone devices anymore. This is important fact.
Once the regulated requirements are fulfilled
(SOLAS 1974, IMO MSC 232(82), IMO A 817(19),
IMOA694(17),IMOMSC191(79),IHOSPS662010,
IMO SN/Circ. 248), the system can
be ‘…accepted as
complying with the uptodate chart’. This fact
determines further way of understanding and
conceptionofECDISasaprimary navigationmean,
butentailsnumberofconsequences.
3.1 Generalreview
According to (IMO MSC. 232(82), IMO A. 817(19)
1995) performance standards, atleast three
mandatory devices
should be connected in ECDIS;