769
1 INTRODUCTION
Theelectronicnavigationisbecomingmoreandmore
common,especiallyonboardmerchantships.Todayʹs
seafarer needs a tool with a similar standard of
qualityasthetraditionalstandardpaperchart(SNC),
which, however, corresponds to the requirements of
the new navigational era. The electronic charts
provide
significant benefits in terms of navigation
safety and improved operational efficiency. The
ECDIS (Electronic Chart Display and Information
System) has become an important step in the
developmentofshipping,whichmeansthetransition
frompapertodigitalnavigation(Weintrit,2009).The
ECDIS installation schedule came to the end in July
2018,therefore,moreandmorevessels(notonlythose
underSOLASconvention)useelectronicnavigational
chartsasabasicwayofnavigationoverapaperchart
system.Butwhatisthesituationonthechartmarket?
Unfortunately, even now after over thirty years of
developing international standards for ECDIS and
electronic
charts, there are still misunderstandings
amongthemaritimecommunityandnoteverythingis
clear and obvious. The confusion seems to be quite
considerableamonguntrainedseafarers,shipowners,
chart distributors, and even among various
authoritiesaroundtheworld. The authorʹs intention
istodispelalltheseaccumulateddoubts.
2
ELECTRONICNAVIGATIONALCHARTS
An Electronic Navigational Chart (ENC) is a digital
representation of paper charts, called now SNC
(Standard Navigational Charts), a digital file
containing all chart information necessary for safe
navigation, as well as supplementary information
required to plan voyages and avoid groundings
(route planning and route monitoring). ENCs are
Clarification, Systematization and General Classification
of Electronic Chart Systems and Electronic Navigational
Charts Used in Marine Navigation.
Part 2 - Electronic Navigational Charts
A.Weintrit
GdyniaMaritimeUniversity,Gdynia,Poland
PolandBranchoftheNauticalInstitute,UK
ABSTRACT:Inthearticle theauthor attemptstoisolate,clarify, systematize, andclassify various typesand
kinds of electronic navigational charts used in electronic chart systems, their specificity, operational status,
significance and role they play. In particular he tries
to promote internationally standardized vector charts
ENCs(ElectronicNavigationalCharts),andrasterchartsRNCs(RasterNavigationalChart),aswellasmilitary
DigitalNauticalCharts(DNCs),HighDensityBathymetricENCs(bENCs),PortENCs(PENCs),InlandENCs
(I‐ENCs),ThreeDimensionalDigitalNauticalCharts(3DNCs)andothers.Hepresentsgeneralclassificationof
electronic charts data bases taking into account the following criteria: spatial dimension, data types (data
format), official status, international standards, consistency, level of detail of bathymetry, data confidence
(reliability, accuracy), navigational purpose, and indirectly also the compilation scale of the chart, size and
arrangementofcells.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 12
Number 4
December 2018
DOI:10.12716/1001.12.04.17
770
official vector‐based electronic charts designed to
meet the relevant chart carriage requirements of
SOLAS convention. When displayed within certain
parameters,andusingatypeapprovedECDIS,ENCs
fullysatisfySOLASchartcarriagerequirements,and
so can be used as the primary means of navigation.
ENCboastselectronicfeaturesthat
paperchartslack.
For instance, a navigator can integrate GNSS/GPS
data‐which tells a navigator his precise position
coordinates online in real time‐with ENC data.
Navigator can also integrate data from other
Geographic Information Systems (GIS), real‐time
hydro‐meteorological data, like tide, current, and
winddatatoenhance
ENCcapabilities.
The inclusion of these functions can provide a
more complete and accurate picture of marine
environment. Vessel using ENCs can detect an
obstruction in advance and check planned routes to
avoidcrossinghazardousareas.The electronic chart
systems used to view ENCs can display alarms,
warnings (indications) and regulations
relating to
areas in which a vessel passes, and can sound an
alarm if the vessel is approaching the obstacle too
much.
Table1.ElectronicNavigationalChartsversusPaperCharts(Weintrit,2009)
__________________________________________________________________________________________________
PaperChart(SNC)ElectronicChart(ENC)
__________________________________________________________________________________________________
fixedscalesheet,fixeddisplaysize,
fixedNorth‐uporientation(usually),fixedresolution,
fixedsymboldefinition,variabledisplayscale,
fixedsymbolarrangementandapplicationwithrespecttoNorth, variabletypesandamountofinformation,
limitedpapersize,variousorientationwithrespecttoNorth,
limitedtypesandamountofinformation,varioussymbol
arrangementandapplication,
limitednumberofcoloursandcombineduse.varioussymboldefinition,
variousnumberanduseofcolours.
__________________________________________________________________________________________________
Figure1.ClassificationofelectronicchartdatabaseaspiringtoachievetheIMOofficialstatusofENCandRNC(Weintrit,
2001and2009)
2.1 DifferentTypesofElectronicCharts
Not all electronic charts are in same format; many
differentformatsexistforelectroniccharts.However,
two major types are now in use on merchant ships,
theyarevectorchartsandrastercharts.
Raster Charts. Raster chart is essentially an
electronic picture of the
familiar paper chart,
obtained through an accurate, detailed scanning
process. Raster charts therefore have exactly the
sameinformationasthepaperchart.Anexample
of raster charts are Raster Navigational Charts
(RNCs)thatconformtoIHOspecificationsandare
produced by converting paper charts to digital
imagebyscanner.The
imageissimilar to digital
camera pictures, which could be zoomed in for
moredetailedinformationasitdoesinENCs.The
IHO Special Publication S‐61 provides guidelines
forproductionofrasterdata.
Vector Charts. Vector charts utilize a vector
database to build the chart display. This data is
stored in layers and records every nautical chart
feature such as coastlines, buoys, depths, lights,
etc. These features and their attributes such as
position,color,size,shape,andothersarestoredin
a database allowing them to be selectively
displayedandinterrogated.Anexampleofvector
771
charts are Electronic Navigational Charts (ENCs)
that are the chart databases for ECDIS, with
standardizedcontent,structureandformat,issued
for use with ECDIS on the authority of
government authorized hydrographic offices.
Accordingto theIHO standards(IHO S‐52,2010;
S‐57, 2014) ENCs contain all chart information
necessary
for safe navigation, and may contain
supplementary information in addition to that
containedinthepaperchart.ENCsareintelligent,
because systems using them can be programmed
togivewarningofimpendingdangerinrelationto
thevesselʹspositionandmovement.
Table2.RasterChartsversusVectorCharts
__________________________________________________________________________________________________
RasterChart(RNC)VectorChart(ENC)
__________________________________________________________________________________________________
Chartdataisadigitized“picture”ofachart(scannedchart). Chartdataisorganisedintomanyseparatefiles.
Alldatainonelayerandoneformat.Itcontainslayerinformationtoproducecertainsymbols,
Withrasterdata,itisdifficulttochangeindividualelement lines,area,colours,andotherelements.
ofthechartsincetheyarenotseparatedinthedatafile. Withvectordata,itcanchangeindividualelementswith
Thedepthunitscannotbechanged.additionaldata.
Thereisnopossibilitytoʺhideʺinformationonthemap. Gooddisplayatanyscale.
Becauserasterchartsperfectlymatchthe
papercharts,itis Detailedinformationonspecificobjectsofthechart
easywhenunderwaytoworkbackandforthbetween (e.g.lights,buoys).
thewideviewoflargepaperchartsandthesmallsection Abilitytoconfigurechartsandfilterdata.
seenonanelectronicscreen.Lessmemory
isrequiredforstorage.
Thereisnoneedtolearnforseafarersalreadyfamiliarwith Zoominginandoutmakesmovementbetweensmall‐and
papercharts.large‐scalechartsunnoticeableandseamless.
Vectorchartshaveaʺcleanʺlookbecausetheypresentless
informationonanyonescreen.
_________________________________________________________________________________________________
2.2 DataSource
Inthelate1980s,theadventofthedigitaleracreated
opportunityforprivatemanufacturerswhowerekeen
to develop electronic chart systems (ECS) and
proposed digital nautical charts generally obtained
simplythroughdigitizingthepaperchartsproduced
by HOs. Considering the liability aspects, the
International Maritime Organization
(IMO) adopted
Performance Standards for ECDIS in 1995, modified
in2006(IMO,2006),whichincludedaprovisionthat
the associated ENCs had to be issued ‘on the
authority of government authorized hydrographic
offices’. This provision was refined in the
amendments to the SOLAS Convention that were
adoptedin2000and
enteredintoforcein2002.These
amendmentsincludeadefinitionofanauticalchartor
publication as ‘a special‐purpose map or book, or a
speciallycompileddatabasefromwhichsuch amap
orbookisderived,thatisissuedofficiallybyoronthe
authorityofaGovernment,authorizedHydrographic
Officeorotherrelevantgovernmentinstitutionandis
designed to meet the requirements of marine
navigation.’(RegulationV/2.2).Theyincludealsothe
requirementthatGovernmentsundertake to arrange
for the collection and compilation of hydrographic
dataandthepublication,disseminationandkeeping
up‐to‐date of all nautical information necessary
for
safe navigation.’ (Regulation V/9). This means that
electronic charts (even in vector format) created by
private chartmakers cannot receive status of official
chartsforSOLASvessels.
2.2. DataStandard
An electronic navigational chart (ENC) is an official
databasecreatedbya nationalhydrographicofficefor
usewithECDIS.Anelectronic
chartmustconformto
standardsstated inthe IHOSpecialPublicationS‐57
(IHOS ‐57,2014) andS‐52(IHO S‐52,2010) before it
canbecertified asan ENC.OnlyENCs canbe used
within ECDIS to meet the IMO performance
standards for ECDIS (IMO, 2006) and SOLAS
Convention.
ItisobviousthatanofficialECDISservicecannot
beprovidedonanationallevelonly,butrequiresco‐
operationofhydrographicservices.TheIHOdecided
toestablishWorldwideElectronicNavigationalChart
Data Base (WEND). IHO members states are
encouraged to provide information concerning their
onlinechartcataloguesto
theIHOSecretariattokeep
Online Worldwide Chart Catalogue (Jonas and
Weintrit,2005).
ENCs are available through Regional Electronic
Navigational Chart Coordinating Centres (RENCs)
andnationalelectronicchartcentres:e.g.Primar(with
perfect seamless ENC cells with similar density of
chartdetails), IC‐ENC(withBritishstyleENCs with
different
density of details). Distributors like the
United Kingdom HydrographicOffice(UKHO) then
distributethesetochartagents.
The IHO adopted a digital chart standard‐
designated S‐57‐which specifies the structure and
format of ENCs. IMO’s Performance Standards for
ECDISrequirescompatibilitywithS‐57ENCsinorder
foranECDIS
tobetype‐approved;thishasmadeS‐57
a de factostandardforvector charts. Because ENCs
might be subject to unauthorized modification or
illegal copying, the IHO has adopted S‐63, the
standard which define technical details for the
particular method of encryption used, as well as
operating
procedures for charts display systems to
useS‐63 charts.An S‐63chart issimplyaS‐57 chart
thathasbeenencrypted.
The IHO standard S‐57 ver.4 , called IHO S‐100
(IHOS ‐100,2017), givecompletely new significantly
expandedpossibilitiesforthechartmakers.
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Figure2.Norwegian(Primar)styleseamlessENCcells(cell
tocell),(Primar,2018)
Figure3.American/BritishstyleENCcells(differentsizeof
cells–celloncell),(Primar,2018)
Theexistenceofprivatelymanufacturedchartdata
is a fact. It is cost‐effective and economically viable.
Itsvolumeisstillincreasingandithasprovedtobe
meeting a demand of maritime market. The major
data manufacturers (e.g. Transas with data format
TX‐97, C‐Map by Jeppesen with data
standard CM‐
93) offer a high quality and affordable means of
world‐widenavigation,soldthroughglobalnetwork,
includinganeasytoaccesstheupdateservice.
2.3 DestinationSystem
Only ECDIS using the official ENC entitles to
navigate without paper charts! ENCs are the only
routetopaperless navigation.ENCs
areproducedto
the hydrographic standards S‐57. In order to enjoy
official status as ENCs they must accord with the
product specification and be up‐to‐date, thereby
meeting IMO regulations for paperless navigation
usingECDIS.
When relevant ENC chart information is not
available in appropriate form, some ECDIS
equipment
may operate in the Raster Chart Display
System (RCDS) mode using Raster Navigational
Charts(RNCs).
2.4 UpdatingService
If vessel operates with an electronic chart system,
thereisaneedtokeepthechartsup‐to‐date(evenif
they should not be used as a primary means of
navigation).
Forvessels operatingwithECDIS, there
isalegalrequirementtokeeptheelectronicchartsas
up‐to‐date as possible especially if this is your
primarymeansofrecordingyournavigationposition.
UpdatestoElectronicNavigationalChartsshouldbe
issued by HOs at regular interval, for example
weekly,andeach
paperlessvesselshouldbeprovided
withanofficialregularupdateservice.
3 CONFUSIONOVERTHECHARTS
ThesignificantproblemintheuseofECDISliesinthe
charts to be used. The confusion appears to be
symptomatic.Youmust usean ENCin ordertouse
thesystemasan
ECDIS.IfnocompleteENCcoverage
isavailablefortheshipsareaofoperationsyouhave
to use other available charts, and then your system
willloseECDISstatusandturnintoECS.
When the ENC coverage was in the past very
limited,itwasdifficulttogetanoverviewover
which
partsoftheworldarecoveredbyENCs.Itwasmerely
stating the fact that the availability of ENCs was
limited, and thus the possibility to use ECDIS in
practicewaslimited.Theconfusionbegins,whenwe
startspeakingaboutotherlessofficialtypesofvector
charts than ENCs,
and also about raster charts,
includingRNCs.
3.1 ProductionoftheNavigationalCharts
Productionofofficialnavigationalchartshasbeenan
exclusive domain of the national Hydrographic
Officesforalongtime.TheIMOspecifies inSOLAS
regulations that only the charts made by the HOs
meet the carriage requirements for
commercial
shipping.Eachshipmustmeettheserequirementsto
be considered seaworthy by the appropriate
authorities. Some are preaching controversial
opinionsthatthetimehascometostartmoretrusting
theprivatelyproducedcommercialnauticalchartsto
putthemonthesimilarlevelastheofficialonesand
to clarify
the relevant liability issues (Buttgenbach,
2018). The most important thing is that the charts
shouldbereliable, accurate and up‐to‐date. But is it
reallyhappening?
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3.2 Non‐OfficialCharts
ModernIHOstandardssuchasS‐44(IHOS‐44,2008),
S‐57(IHOS ‐57,2014),S‐100(IHOS‐100,2017),andS‐
102havemadeitpossibletoproducedigital chartsof
unparalleledprecision.Itisaknownfactthatnotonly
national
HOs but also private chartmakers are
capable to produce charts of high quality and
reliability. The justification for the monopoly of the
official charts was many times challenged more or
lessrightly(Malie,2003; Buttgenbach,2018;DiLieto
etal.,2018).
Today there is a number of alternatives to the
official ENCs, e.g. Navionics, Transas and Jeppesen
(formerlyC‐Map)havealmostworldwidecoverageof
vector charts where the data is based on existing
paper charts. Unfortunately these charts have not
obtained the status as official, because that they are
private manufacturers and because of the frequency
oftheupdates(usually
monthlyorquarterly)andthe
lack of a controlling authority to approve the
contents.
Figure4.SummaryofENCs:Official–Non‐Official;Vector
‐Raster(Arts,2003)
4 ENCNAVIGATIONALPURPOSES
The concept of separating ENCs into usage bands
providesdataproducerswithamechanismtocreate
cellsdesignedfor six distinctnavigationalpurposes,
each having different levels of content (e.g. contour
intervals) and degrees of generalization. Similar
navigational purposes (see Table 3 below) are also
usedfor
paperchartseries.
Table3.ENCNavigationalPurposes–ENCsBands
_______________________________________________
Subfield ENCCompilationScaleRange
Content/ Navigational
Bands Purpose
_______________________________________________
1Overview <1:1500000
2General1:180000÷1:1500000
3Coastal1:45000÷1:180000
4Approach 1:22000÷1:45000
5Harbour1:4000÷1:
22000
6Berthing>1:4000
_______________________________________________
According to the IHO report, in 2016 the global
coverage of the ENCs was the following: for the
Bands1&2=100%,forBand3=93%,andforBands
4, 5 & 6 = 98%. For paper charts SNCs (Standard
Navigational Charts) the coverage was almost the
same.
Theobservationspresentedbelowarebasedonthe
suppositionthatmostENCswerederivedfrompaper
charts and therefore have similar characteristics in
terms of content, generalization and coverage. It is
assumed that ENCs compilation scale is comparable
itssourcechartscaleanditscellslimitsapproximate
thoseofthe
sourcepaperchart.
Thescalesselectedforportapproach,harbourand
berthing paper charts, are largely dependent on
factors such astheavailable source data, the size of
theharbour andthe extentof theport area.Because
these factors vary depending on the port, the scales
and chart coverage may
vary accordingly. Similarly
coastal charts (usage band 3) also need to take into
account additional factors such as the nature of
coastal area and density of shipping. Therefore, the
scales and ranges selected for these charts may also
vary depending on the area. Small scale charts and
ENC cells often
extend beyond national charting
limits and provide extensive coverage of the high
seas. Their content is usually reduced to significant
navigationalfeatures,andisoftenhighlygeneralized.
Thecompilationsscaleschosenfortheseproductsare
notasheavilyinfluencedbylittoralcoastalconditions
and therefore provide an opportunity for the
development
of harmonized, consistent word wide
chartcoverage.
5 RELIABILITYOFTHECHARTS
5.1 AccuracyoftheNauticalCharts
Navigational charts are basic source of information
for seafarers. They are essential tools for marine
navigation. But how accurate are the navigational
chartsthatweusewhensailing?Allcharts,whether
paper
or electronic, contain data of varying quality
duetotheage,accuracy,reliabilityandcompleteness
of individual surveys. Until now, itwasnoteasyto
assess the reliability of a chart, one had to rely on
declarations of the Hydrographic Offices (the
reliabilitydiagramsforexample)orofchartmakersin
general.
A chart can be treated as a puzzle of
individual surveys pieced together to form a single
image. Most charts contain a mixture of surveys of
varying quality.In general,remoteareasaway from
shipping routes are less frequently surveyed, while
areas of high commercial traffic are often reviewed
with
veryhighaccuracyandcompleteness,especially
whereunder‐keel clearancesaresmall.However,the
majorityofcoastalandinternationalshippingroutes
are somewhere betweenthese two standards, where
risksandchoicesarelesswelldefined.Toassessthese
threats,seafarershavetraditionallyreliedonknown,
butoftenambiguousindicatorsusedon
papercharts,
usually in a source diagram or currently in ZOC
diagram. Details and interpretations often differed
greatly between HOs. Differences in method, detail
and interpretation render this type of quality
informationunsuitableforuseinanelectronicsystem
such as ECDIS, as it prevents use of automated
checking routines
to look along a planned route to
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confirm suitability. To solve this problem, the IHO
developed and published an international system
usedbyallnationswithinitsS‐57ENCs.Thisisthe
“ZonesofConfidence”(ZOC)system. Thedegreeof
reliancewhichcanbeplacedinthedepthinformation
within an ENC can be consistently determined
by
understandingtheZOCassessmentforanarea,then
applyingacommon‐senseapproach.
The Standard Display, which is also a pre‐
arrangedchartdisplay,butwhichcanbemodifiedby
theoperator,andwhichisautomaticallyshownwhen
theECDISisfirstswitchedon.Itcontainsthedisplay
base
plus boundaries of channels etc., conspicuous
features, restricted areas, chartscalebounda ries and
cautionarynotes.
5.2 ZonesofConfidence(ZOC)Categories
There are five basic levels within the ZOC system
(Table.4).Eachdifferinglevelofqualityisreferredto
as a ‘category’withintheoverallZOC system. Each
category is therefore
labelled as ‘CATZOC’ when
queried within the ENC. The categories range from
‘veryhighconfidence’to‘unsurveyed’.Thereisalso
anadditionalcategoryfor‘Unassessed’.
Thus,putinsimpleterms,electronicchartsarenot
thesame,theydiffergreatlyinthedensityandquality
ofpresentinginformation.Seafarersshouldbe
ableto
navigatewithconfidenceinareaswithZOCA1 and
A2classifications.Itisalsounlikelythatanuncharted
danger affecting surface navigation exists in ZOC B
areas. In ZOC C areas seafarers should exercise
caution since hazardous uncharted features may be
expected,particularlyinornearreefandrocky
areas.
A very high degree of caution is required for areas
assessedasZOCD,asthesecontaineitherverysparse
dataormaynothavebeensurveyedatall.Finally,it
isgoodpracticetotreatZOCUareaswiththesame
degreeofcautionasZOCDareas.
Table4.ZonesofConfidence(ZOC)Categories(IHOS‐57,2014;Weintrit,2018;Rutkowski,2018)
5.3 AnalysisoftheReliabilityofCoastalENCs
To put this in perspective, the Table 5 is an overall
analysis of over 14 million square kilometres of
coastal ENCs from 32 nations (IHO S‐67, 2017). The
analysis did not include ports and harbours. What
maybesurprising,accordingto
areportpreparedby
the IHO S‐67, in coastal shipping areas the most
commonassessmentslikelytobeencounteredarethe
following:
ZoneofConfidence(ZOC)B–around30%ofthe
world’scoastalwaters,
ZOCC–around20%oftheworld’scoastalwaters,
ZOC
D – around 20% of the world’s coastal
waters,and
ZOC U – around 25% of the world’s coastal
waters.
It means that only less than 5% of the world’s
coastal waters falls into the category A1 or A2
(Weintrit, 2018). Thus, it should be clear that a firm
understanding
oftheimplicationsofeachconfidence
level should be important for planning the safe
navigationofavessel.
775
As we can see the situation in the most busy
maritimewaterareas(e.g.inEnglishChannel)looks
no so bad, but it is very far to be perfect, the B
category dominates, areas covered by categories A1
and A2, unfortunately, do not impress. But what
about the rest of
the world then? Although these
percentages may vary from place to place, the key
pointisthat the standards of surveyinginports are
only very rarely encountered outside those ports.
Therefore,shipsareatgreatestriskawayfromports,
even though depths may be deeper. An
understandingofhow
muchconfidencecanbeplaced
in the data within an ENC is therefore the most
important. Do we need to revert to paper charts in
areaswheretheENCCategoryZoneofConfidenceis
settoCorless?No,wedon’t.Thesamedataisused
for a paper charts
and ENCs, so they are not more
accuratethanothers.
Table5.SeaAreasCoveredbyENCs withInformationontheZOCCategory(IHOS‐67,2017)
6 BATHYMETRICENCSINCONFINEDWATERS
HydrographicOffices haverealisedthat bathymetric
data is not sufficiently represented in ENCs.
Electronic charts with greater scale and bathymetric
contentthananyHydrographicOffice’sENCarenot
a novelty for many ports around the world. Such
chartsarenormallyproducedbyPortAuthoritiesand
areusedbymarinepilotsonthePortablePilotUnits
(PPU). Some HOs experimented with High Density
(HD) Bathymetric Electronic Navigation Charts
(bENCs) for ports. These ENCs – like any other
officialones–couldbeavailablebothtoships’crew
usingECDISandtoMarinePilots’PPUs(DiLieto
et
al.,2018;Moggert‐Kageler,2018).
6.1 HighDensityBathymetricENCs(bENC).
The first innovation of High Density Bathymetric
ENCsisaboutgivingthepossibilitytovisualisesafety
margins with higher resolution than a standard
harbour ENC. The second innovation of bENCs is
about providing more detailed information on deep
soundings
within navigable areas, which is an
important piece of information to anticipate the
effects of hull‐seabed interactions. This was not
possible by looking only at harbour ENC’s dredged
areasthatusuallycovermostoftheconfinedwaters
with single maintained depth values. These two
conceptsbringENCstoexceed
themereequivalence
to paper charts and to take full advantage of high
accuracy electronic navigation systems to monitor
real‐time ship’s position and heading when safety
margins are tight. It is essential that bathymetric
ENCs become available to both ECDIS and PPUs
users because the risk of ever decreasing safety
margins to conduct vessels in confined waters
requirestheship’screwtobeonthesamepagewith
themarinepilot,especiallywhen safetymarginsare
small(DiLietoetal.,2018).
High Density Bathymetric ENCs can be created
and maintained in S‐57 format. The challenge is to
understand
potentialandconstraintsofexistingIHO
standards. Among High Density Bathymetric ENCs
(bNEC), we can distinguish several other groups of
chartsontheneedsandpurpose,amongothersPort
ENCs,PreciseENCs,InlandENCs,etc.Accordingto
Seefeldt (2011) the Port ENC standard should be an
independent but complementary to standard
of
maritime ENC and Inland ENC (see Fig.5 and 6
below).
Figure5.ThePortENCcomponents(Seefeldt,2011)
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Figure6.ENCgradationincludingthePortENC(Seefeldt,2011)
6.2 ResearchInstrument
Because most of the national HOs only produces
ElectronicNavigationChartsforharbourusage,some
ports investigated the possibility of producing
‘Berthing’ ENCs containing high density depth data
to support decision‐making within the port. For
example,thePortofRotterdamstartedapilotproject
toproduceS
‐57ENCsoftheareacoveredbytheport
morethantenyearsago.Thegoalofthisprojectwas
to produce daily high density ENC updates that
incorporateddailyhydrographicsurveysofthearea.
IttookafewyearstotakethehighdensityENCinto
productiondueto
manyconversiontoolsthathadto
be developedandperformance problems in creating
depth areas at a contour interval of only 10 cm (Di
Lietoetal.,2018).
7 OTHERTYPESOFDIGITALCHARTS
7.1 ElectronicNavigationalChart(ENC)withAdditional
Militarylayers(AML)forWECDISuse
Theconceptofadditional
militarylayers(AML)was
introduced in 1995 with the intent to define a
standardizedformatfornon‐navigationaldata.Since
thattime,variousNorthAtlanticTreatyOrganization
(NATO) standardization agreement documents
concerning AML data and Warship Electronic Chart
Display and Information Systems (WECDIS) have
been created. Using precise military integrated
navigation system the sophisticated electronic chart
system designed to meet the specific navigational
demands of the military market, the strengths and
weaknesses of how AML data interacts with other
datatypes, primarilyENC data,withintheWECDlS
were identified. We might also consider referring to
the concept of Marine Information Overlays
(MIO)
which have been used in the Marine Electronic
Highway project, and whose use are gathering
supportwithinthee‐Navigationdiscussion.
7.2 DigitalNauticalChart(DNC)
The largest of the non‐S‐57 format databases is the
DigitalNauticalChart(DNC)producedaccordingto
a military specification. The DNC
is a vector‐based
digital product that portrays significant maritime
featuresinaformatsuitableforcomputerizedmarine
navigation. The DNC is a general purpose global
databasedesignedtosupportmarinenavigationand
Geographic Information System (GIS) applications.
DNC data is only available to the U.S. military and
selectedallies.It
isdesignedtoconformto the IMO
Performance Standard and IHO specifications for
ECDIS.
What is the difference between DNC and ENC?
DNC andENCchartsare“vector” charts where the
data can be found in layers which can be overlaid
onto a display. A Digital Nautical Chart (DNC) is
produced by NGA in accordance with DIGEST C
Vector Product Format (VPF). While both ENC and
DNC are vector charts, they have different spatial
data models. An ENC has two layers (skin of the
earthandeverythingelse),whileaDNChas12layers
of information. An ECDIS must transform the
ENC
intoa“System”ENC(SENC)foruse.Thisessentially
meansfulltopologymustbeconstructedfromtheless
complete chain‐node topology of the ENC. DNC is
topologicallycomplete,i.e.all12layersofinformation
are fully attributed, and can be “directly read” by
WECDISorECDIS‐N(ECDIS
Navy).
7.3 OffshoreElectronicNavigationalChart
Inoffshoremining industry, such as Offshore Oil &
Gas,ExploitationoftheSeabed,Telecommunications,
Fishing,AggregateExtraction,Diving,sometimesare
usedthreedimensionaldigitalnauticalcharts3DNCs.
In Dynamic Positioning System are used either two
dimensional ENCs or 3DNCs. Sometimes it is
convenientto
presentsomedetailsinaspatialway.
7.4 ThreeDimensionalDigitalNauticalCharts(3DNC)
Themultibeamseafloormappingtechnologymakesit
possible for the first time to map and to reveal all
hazardstonavigationwithhighconfidence.Iftaken
into use for shallow water areas with significant
trafficdensity
suchasportentrances,ports, riversand
777
other inland waterways, it can mean a significant
increase in the safety for shipping. For ports, the
multibeamtechnologycanbehelpfulforminimising
thecoastofdredging.Itcanalsobeusedforefficient
inspection of breakwaters, bridge foundations and
othermanmadeconstructionsandforlocatingdebris
onthe
bottom.Forsurveyingofcanalsandrivers,the
increase in efficiency is very substantial, since the
survey lines are now parallel to the shoreline. The
3DNC is most probably the next step in ENCs
development.
7.5 InlandElectronicNavigationalChart(I‐ENC)
InlandENCs(I‐ENCs)areofficialdigitalvector
charts
produced by inland waterway authorities in
accordancewiththeIHO’sproductspecificationS‐57,
extendedforuseoninlandwaterways.InlandENC(I‐
ENC)meansthedatabase,standardizedastocontent,
structure and format, issued for use with Inland
ECDIS.InlandENCcomplieswiththeIHOstandards
S‐57 and
S‐52, enhanced by the additions and
clarifications of this standard for Inland ECDIS. The
Inland ENC contains all essential chart information
andmayalsocontainsupplementaryinformationthat
maybeconsideredashelpfulfornavigation(Weintrit,
2010). I‐ENCs follow the IHO S‐57 data exchange
standard, which is
recognized by software vendors
and government hydrographic offices for electronic
chartapplications.Becauseofthetechnicalsimilarity
betweenI‐ENCsandSOLASENCs,bothcanusually
be displayed on both ECDIS and inland navigation
systems. However, the inland I‐ENC standard is a
superset of the ENC standard. Therefore, an ECDIS
system will not normally display inland waterway
specificobjectsandsymbolscorrectly.
8 NEXTGENERATIONENCS‐101
8.1 IHOStandardS‐100
AftermorethantwodecadesofusingIHOS‐57data
fornavigation,thetimehascomeforanewstandard,
moreversatile,withagiledevelopmentand
constant
evolution, which can address today’s navigational
and non‐navigational needs; according with
international geospatial standards, integrated with
the GIS world. These are inherited characteristics
from the S‐100 Universal Hydrographic Data Model
(IHOS‐100,2017)intotheS‐101ProductSpecification
forElectronicNavigationalChart data.Aftertheuse
of a “semi‐frozen” and rigid S‐57 specification, the
objectiveistoreplaceitwithS‐101.Althoughthisnew
specificationisabigstepintomodernity,itdoesnot
representaradicaldeparturefromitspredecessor;it
keeps many of the S ‐57 attributes and enhancing
elements while
complying with ISO geospatial
standards, which will make these data sets very
useful in spatial data infras tructures, GIS and e‐
Navigation (Weintrit, 2011). The intention is not to
developIHOS‐101inavacuum,buttoactivelysolicit
input from software and equipment manufacturers
andtheultimateend‐user:the
seafarer.TheStandard
Display, which is also a pre‐arranged chart display,
butwhichcanbemodifiedbytheoperator,andwhich
is automatically shown when the ECDIS is first
switched on. It contains the display base plus
boundaries of channels etc., conspicuous features,
restricted areas, chart scale boundaries and
cautionarynotes.
8.2 DynamicENCContent
ThegreatadvantageS‐101willhaveovertheexisting
S‐57ENCproductspecificationistheintroductionof
dynamic, machine readable feature and portrayal
catalogues.Thetermdynamicisusedtoindicatethe
ability to support evolutionary change in an almost
continuouswaywithout
impactingonexistingusers.
While similar in content to the current S‐57 object
catalogue and the S‐52 presentation library, IHO S‐
101willimplementthedynamicconstructsprescribed
byS‐100.InS‐101,therelationshipbetweenfeatures,
attributesandenumeratesaredefinedwithinasingle
featurecatalogue.
Although,partofthestandard,the
feature catalogue will be built through reference to
the registry that provides the definition of the data
content in a machine readable form, thus allowing
ECDIS to easily update on board systems via a
straightforwardsoftwareupdate.
Another future‐proof solution may be dynamic
electronic
navigationalcharts,changingthecontentof
the chart in time, e.g. changing the course of the
isobaths (contour lines) on the chart, taking into
accountthedynamicphenomenonoftides.
9 SYSTEMELECTRONICNAVIGATIONAL
CHART(SENC)
A SENC is an acronym for System Electronic
Navigational Chart. An ECDIS converts ENC
data
intoitsown internalSENCformat for optimal chart
image creation. SENC data can differ between
manufacturers. The System Electronic Navigational
Chart (SENC) means a database resulting from the
transformationoftheENCbyECDISforappropriate
use, updates to the ENC by appropriate means and
other data added by
the seafarer. It is this database
that is actually accessed by ECDIS for the display
generationandothernavigationalfunctionsandisthe
equivalenttoanup‐to‐datepaperchart.
In2006theIMOmodifiedalittlethedefinitionof
the SENC: System Electronic Navigational Chart
(SENC) means a
database, in the manufacturer’s
internal ECDIS format, resulting from the lossless
transformation of the entire ENC contents and its
updates (IMO, 2006). This slight correction of
wordinginSENCdefinitionallowedthebypassingof
existing arrangements and the emergence of such
seeminglyexotictiesasC‐Map(Jeppesen)withNHS
as
well asBritishAdmiralty(UKHO) withTransas‐
TADS(TransasAdmiraltyDataService).Thusanew
ENC with the status of SENC appeared on the
market.Theperceptionofwhatisofficialvectordata
alsodefinitelywaschanged(Fig.7).
778
Figure7.Whatshouldbeconsideredasofficialvectordatanowandwhatshouldhavebeenconsideredofficialdataafter
1995until2006(Weintrit,2009)
779
Figure8.Generalclassificationoftheelectronicchartstakingintoaccountvariouscriteria,amongothers:spatialdimension,
types of data (data format), officiality, international standards, seamlessity, detail level of bathymetry, presentation of
details,dataconfidence(reliability,accuracy),navigationalpurposesandindirectlyalsothecompilationscaleofthechart
andcell
size
In order to get efficient data structures that
facilitatetherapiddisplayofENCdata,mostECDIS
converteachENC datasetfromS‐57intoan internal
machine‐language format called SENC or System
ENC – which is optimised for chart image creating
routines. Most ECDIS software manufacturers have
theirown
SENCformat.Inordertotakeadvantageof
the efficiencies of delivering ENC data in a SENC
format, the IHO has authorised an optional
distributionmechanismcalledSENCdelivery.Thisis
inadditiontothestandarddistributionofENCinS‐
57 format. In this case, a RENC delivers the
S‐57
based ENCs to an authorized chart data distributor
whothenperformsanENC‐to‐SENCconversion, and
deliverstheresultantSENCtotheenduser.However,
itisuptoindividual HydrographicOfficesdecision.
NotallHydrographicOfficesallowtheirENCstobe
deliveredbydistributorsasSENCs
(IHOS‐66,2018).
10 CONCLUSIONS
AElectronicNavigationalChartshaveimprovedthe
safety of navigation and the efficiency of operations
forseafarers who have welcomed digitaltechnology
positively. The delivering a portfolio of nautical
chartscoveringthewatersofacountryisnolongeran
end in itself but one
of the many applications of a
nationalmarine spatialdatainfrastructure thatmust
beconsideredasapublicgood.Thereisnodoubtthat
in the years to come the volume of ENCs will
780
increase.However,itisveryunlikelythatENCswill
ever have a 100% world‐wide coverage. Hence the
chance for private chartmakers. It seems that the
private sector can and should play a major role in
developingtoolstomanageefficientlythatdatabase
as well as in inventing and
developing a variety of
value‐addedproductsandservicesderivedfromthat
infrastructure. But as long as shipping remains a
significant component of the world trade
infrastructure, there will continue to be a
substantiatedneedfor‘official’nauticalcharts.
Unfortunately, most navigational charts are an
amalgamation of geospatial information collected
using different techniques at different times. We
should be aware of this and always remember that
ENCsdonotalwaysmeanNew!ENCsthatareonthe
markettodaydonotalwaysdepicttherealworldas
accurately as would be desired. ENCs (and paper
charts) are compiled from multiple data
sources,
some modern and comprehensive, some old (even
ancient) and others from all stages in between.
Unfortunately CATZOC’s was not well understood,
not liked, nor allowed seafarers to adequately make
decisions based on data quality. Because of these
problems and despite the effort and resources
dedicatedbyHOstopopulate
CATZOC,theIHOhas
agreedthatitwillnotbeusedinthefutureS‐101ENC
productspecification.The newindicators haveto be
useful and easy for the seafarer to understand
(Powell,2011).Thenext‐generationservicesforports,
e.g. bENC, distributed using IHO S‐100 based
standards should
be a leading trend on the market,
because they have great value for the navigation
community, improving the safety and efficiency of
ships.
The clarification and general classification of
electronic navigational charts used in marine
navigation was presented in this article taking into
consideration the following criteria: spatial
dimension, types
of data, officiality, international
standards, seamlessity, detail of bathymetry, data
confidence (reliability), navigational purposes (chart
scale/cellsize),andmutualspatiallayoutofthechart
cells.
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