287
1 INTRODUCTION
Virtualaidstonavigation (AtoN)aredefinedbythe
International Association of Lighthouse Authorities
(IALA) as something that “does not physically exist
butisadigitalinformationobjectpromulgatedbyan
authorizedserviceproviderthatcanbepresentedon
navigational systems” (IALA O143). Truly virtual
aidsthatdonotrequirephysica
linfrastructureofany
kindarestillrelegatedtothefuture.However,similar
capabilitiesarepresentlybeingimplementedthrough
the use of Automated Identification System (AIS)
radio‐based devices that can project their presence
directlyfromabuoyorotherphysicallocationsuchas
abridgeabutment.AISradio AtoN areelectronic in
nature and dist
inguished from physical AtoN with
the addition of an “e” to the AtoN designation
(eAtoN). They can project their presence to remote
locationswhere,forexample,abuoyshouldexistbut
placementand/ormaintenanceofaphysicalAtoNis
toodifficult.Theintendedlocationmustbeintheline
of sight of the very high frequency (VHF) radio
required to originat
e AIS transmissions. One such
example is an Isolated Danger mark located on
Tarapunga Rock in Doubtful Sound near the South
IslandofNewZealand(MarinetrafficVIRT).
Thisconceptisrevolutionarytovesselnavigation
inmuchthesamemanneraswasthei
ntroductionof
radar–withmanyofthesameproblemslikelytobe
encounteredintermsoftrainingandoperation.Real
potential exists to instill new vessel navigational
Correlation of Virtual Aids to Navigation to the Physical
Environment
R.G.Wright
GMATEK,Inc.,Annapolis,MD,USA
WorldMaritimeUniversity,Malmö,Sweden
M.Baldauf
WorldMaritimeUniversity,Malmö,Sweden
HochschuleWismar–UniversityofApplied Sciences:Technology,BusinessandDesign,Rostock,Germany
ABSTRACT: Virtual electronic aids to navigation are being introduced into the present short range aids to
navigationsystemintheformofAutomatedInformationSystemradio‐basedaids.Researchisalsounderway
into the development of their equivalents for use in regions tha
t feature hostile environments, are poorly
chartedandlackanyinfrastructurewhatsoevertosupporttraditionalorradionavigationaids.Suchaidsare
entirelyvirtualinnatureandexistonlyasadigitaldataobjectthatresideswithinanelectronicnavigationchart
for display to mariners through an Electronic Cha
rt Display and Information System. They are at present
experimental innature, and are not intended to replace existing physical or radio‐based aids to navigation.
Resultsofresearcharedescribedintermsoffulfillingtraditionalnavigationaidfunctionsandthedevelopment
ofnewfunct
ionsthatareonlypossibleusingvirtualaids.Theiradvantagesindesignandimplementationare
highlighted, as are their limitations and shortcomings as compared to present methodologies. Notable,
however, is the approach used to overcome limitations and shortcomings by considering attributes of the
physicalenvironmenttoensuretheirproperlocationanddisplayofcorrectcharact
eristics.Suchanapproachis
uniqueinthemodernworld,yetitemulatesancientmethodsofnavigationusingknownlandmarksandterrain
features.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 10
Number 2
June 2016
DOI:10.12716/1001.10.02.11
288
capabilitiesthatcannotbeachievedusingtraditional,
physical AtoN. However, the probability of
encounteringmanylimitationsandfragilitiesunique
to virtual eAtoN is high, and it is necessary to
anticipate and adequately prepare for such
eventualities to ensure safety of navigation is
maintained.
This paper describes research into the
development
of truly virtual eAtoN that do not
requireradiotransmittersorotherphysicalpresence
at the eAtoN location. Significant portions of this
research addresses eAtoN needs critical to their
properinstallationandverificationofperformanceby
authorizedserviceprovidersandsafeandreliableuse
bymariners.Anexpandedrangeof
eAtoNphysical ,
performance, environmental and computational
factorsareconsidered in this analysis. Strategies are
also provided to overcome some of the potential
vulnerabilitiesofsuchdevicesatvariouspointsinthe
eAtoN lifecycle to avert threats by opportunists to
render such devices themselves useless or even
hazardoustonavigation.
2 PHYSICAL
ATONVS.VIRTUALEATON
PhysicalAtoNhavebeenusedforthousandsofyears
to guide vessels along their routes and provide
assurance of safe passage using known landmarks
andstructurestoindicatesafewaters.Inthemodern
era technology has provided us with buoys,
lighthouses, light ranges, day marks and
other
devices to accomplish this capability. AtoN
complementedwithradar,depthsounders,precision
positioning and timing devices broadens situational
awarenessbyhelpingidentifyenvironmentalfeatures
andtrackingvesselprogresswhileunderway.
VirtualeAtoNareintendedtosupplementandnot
replace existing AtoN in areas where the timely
marking of hazards to
navigation can be performed
faster and more effectively than placing physical
AtoN. This may be on a temporary basis until
physical AtoN can be installed such as in marking
new wrecks or where previously uncharted hazards
tonavigationaredetected.Theycanalsobeinstalled
onapermanentbasiswhere
theuseofphysicalAtoN
is problematic or not possible. This includes coral
reefs where sinkers cannot be placed due to their
adverseenvironmentaleffects,intheArcticwhereice
movementcancarryawayphysicalAtoN,andalong
riversandtributarieswherewaterlevelsandchannel
locations are subject to frequent
change. Another
possibility is that eAtoN functionality can provide
flexibility in terms of purpose and positioning that
may be tailored to the unique requirements of
individualvesselsfordeterminingadequatewidthsof
channels, placement locations and other capabilities
such as aid to vessels having lost their way and in
need
ofpositionassistance.
3 EATONIMPLEMENTATIONTECHNOLOGIES
The IALA definition of a virtual aid to navigation
cited earlier provides no direction as to the
implementation technologies through which such a
capability may be achieved. However, earlier
guidancerecognizedthatAIScanbeappliedtoAtoN
tofurtherimproveandenhanceservices
tomariners
and assist AtoN authorities to ensure the safe
provisioningofsuchaidstonavigationasthevolume
of traffic justifies and by the degree of risk (IALA
G1081).
The use of AIS to effect eAtoN implementations
must rely on physical infrastructure to accomplish
their objectives. This in itself
is not problematic in
areas where ready access is available and adequate
financialresourcesexist toinstall andmaintainsuch
physicalinfrastructure.However,thisisnotthecase
over vast portions of the planet where eAtoN
capabilities are needed most – the Arctic and in
sensitive tropical regions. Indeed, regions that
are
without adequate financial resources and those
affectedbywarcanbenefitfromtheabilitytorapidly
install eAtoN without physical infrastructure that
fulfilltheIALAdefinition,“doesnotphysicallyexist
butisadigitalinformationobject”.Suchanapproach
requiringnophysicalinfrastructurehasrecentlybeen
presentedthatcan
overcomeotherlimitationssuchas
the lack of hydrographic survey, sporadic and low‐
bandwidth communications, and an absence of
governmentsupport(WrightandBaldauf2014).Both
suchimplementationsrequireeAtoNpresentationon
navigational systems, with the primary system for
navigation being the Electronic Chart Display and
Information System (ECDIS) (MSC 82).
AIS signals
are also presented on radar and other appropriate
displays.
AISeAtoNhavebeendeployedalongbothcoasts
of the United States, in the Great Lakes and in the
interioralongportionsofthewesternrivers.(Lewald
2015). Deployment of these eAtoN is being
accomplishedinaneffortto
bestdeterminetheiruse
and application for future waterway guideline
development. Descriptions may be found in Local
Notice to Mariners chart corrections and illustrated
eAtoNportrayalsonpapercharts,electronicnautical
charts(ENCs)andradarfor:
Physical AIS eAtoN: AIS signal broadcasts
originatefromaphysicalAtoN,
SyntheticAIS
eAtoN:AISsignalsoriginatefroma
remote AIS base station and are broadcast to a
locationwhereaphysicalAtoNexists,
Virtual AIS AtoN: AIS signals originate from a
remote AIS base station and are broadcast to a
location where no physical AtoN exists but are
displayedonENCs
andECDIS.
(USCG2014;seealsoIALAG1062).
TheUSNationalOceanographicandAtmospheric
Administration(NOAA)announcedanexpandedset
ofsymbolsusedtoportrayAISeAtoNonECDISand
that NOAA charts would be updated to add AIS
eAtoNlocations(OCS2014).Thesesymbolsincludea
magenta radio ring surrounding
the AIS eAtoN
reflectingtheradiotransmissionofthesignal,which
doesnotapplytonon‐AISvirtualeAtoN.
289
4 CHARACTERISTICS
The term “characteristics” when used in relation to
AtoN have generally referred to their physical and
performance aspects as can be readily seen and
measured to determine whether they are “watching
properly”whichis defined bytheU.S. Coast Guard
as, “an aid to navigation on its assigned
position
exhibiting the advertised characteristics in all
respects” (USCG 2005). However, with the
introduction of eAtoN that exist solely as digital
information objects this concept has become
somewhat muddled. Even virtual eAtoN have a
physicalpresenceonnavigationdisplaydevicessuch
asECDISandradar.
Thefollowingparagraphsattemptto
clarifythese
issues by introducing their digital representations
within the context of characteristics by which an
assessmentofwatchingproperlymaybedetermined.
AdiscrepancyisdefinedasanyfailureofanAtoNto
display its characteristics as described in the Light
List or to be on its assigned position. When
a
discrepancy is reported, a response level for its
correction is determined based upon severity and
availabilityofassets(USCG2005a).
Thelinesofdemarcationastowhomdiscrepancies
are to be reported must also be redrawn. The US
Coast Guard is the cognizant organization for
reporting AtoN discrepancies, while
NOAA is
cognizant for charting discrepancies that include
ENCs and ECDIS. However, if AIS or virtual (non‐
AIS)eAtoNareportrayedincorrectlyonachartthis
occurrence should also be reported to the US Coast
Guard.
4.1 AtoNCharacteristics
FortraditionalAtoN,twomainaspectsoftheirdesign
encompass various characteristics
that must be
verified to determine they are watching properly.
Theseinclude:
Physical,and
Performance.
Physical AtoN characteristics consist of nominal
operatinganddiscrepantconditionsandincludetype
(buoy, daymark, range, lighthouse, racon) color,
shape, numbering, light features (red/green/yellow,
flashing/ steady/occulting), sound features
(bell/gong/horn/ whistle), position (lat/long, on
station, off station, adrift, missing, not marking best
water) as well as condition (sinking, stranded,
capsized,excessiverust).Performanceaspectsinclude
light and sound intensity, racon (operational, not
operational,operatingimproperly),rhythmsandrates
ofinstalleddevices,andvisibility(dayboardsfaded,
lights/numbersobscured),etc.(USCG2010).
AtoNaredocumentedand
describedindatabases
(ATONIS/USAIMS, ENC) and data products (e.g.,
LightList,NoticetoMariners,CoastPilot).However,
thesedataobjectsand representations are secondary
to their physical manifestation in terms of
performance.Indeed,physicalAtoNhaveexistedand
stood watch properly for centuries with little more
representation as “data objects”
than a written note
onahand‐madechart.
4.2 eAtoNCharacteristics
Both physical and synthetic AIS eAtoN share the
characteristics cited in the previous paragraph with
their associated physical AtoN that must be
considered during verification and when reporting
discrepancies. However, this does not necessarily
applyto AISornon
‐AISvirtual eAtoNsince neither
are associated with a physical AtoN. Although the
IALA definition of virtual AtoN describes them as
data objects, they actually do exist in the physical
sense when they are depicted on a navigational
display to be observed and acted upon by a
watchstander. The physical
characteristics of AIS
eAtoNincludethesymbolsforphysical,syntheticand
virtual; and non‐AIS virtual (USCG 2014). ENC
depictionofphysicalcharacteristicsforvirtualeAtoN
(AIS and non‐AIS) on ECDIS includes symbols for
cardinal marks (N/E/S/W), lateral marks (IALA A/B
port and starboard), isolated danger, safe water,
specialpurpose
andemergencywreckmarking(OCS
2014). The bulk of eAtoN characteristics exist in the
formof dataobjectrepresentations inthe domainof
theauthorizedserviceprovider.IntheUnited States
this is the Coast Guard and NOAA. These
characteristicsincludetheLightListnumber,typeof
aid,name,position,
class,inspectiondatesandother
information.
eAtoNperformancecharacteristicsaredetermined
inpart by the specificationsfor each specificdevice.
From a practical perspective for operational
verificationtheyeitherworkasspecified(operational)
or don’t work (not operational) in much the same
fashionasaraconinstalledonAtoN.
4.3 Data
ObjectCharacteristics
Recently efforts have been undertaken by IALA to
defineacommonstructureresultinginthecreationof
a Product Specification for AtoN Information (IALA
PS1). This specification is intended to include
informationaboutlights,buoys,beacons,racons,AIS
andsoundsignalsandcanalsoformthebasisfor
the
exchange of virtual AtoN information. Figure 1a
summarizesthekeyelementsoftheAtoNapplication
schemainitscurrentformwhilefigure1bintegrates
theessentialelementsofvirtualeAtoN.
Critical to this schema is the establishment of
single and group virtual eAtoN that can share
geospatial model point, curve
and surface data to
providenewcapabilitiesforvirtualeAtoNoperation.
Thisisaccomplishedthroughinheritanceofattributes
between group virtual eAtoN and the individual
constituent virtual eAtoN elements. Included is a
capability for live comparison between known
hydrographic data used for chart production and
single‐beam echosounder data obtained
from own
vesselsensors tohelpdeterminethevalidityofGNSS
positioning information. Additional capabilities can
include automated verification of virtual eAtoN
watching properly, which may also be extended to
physicalandAISeAtoN.
290
Figure1. Virtual eAtoN application schema embedded
withintheIALAAtoNInformationProductSpecification
1XX,draft0.0.5–June2013.
4.4 VirtualeAtoNAdoption
ExamplesofvirtualeAtoNrealizedasbeacons,areas
and limits, and tracks and zones in the text that
follows are provided to illustrate functions that are
possible. The capabilities described to employ these
functions are also illustrative, as are the specific
characteristics that have been described for
implementation. Determination of virtual eAtoN
adoptionforfuturetest,evaluationand/oroperational
use must be made by competent national authority
afterthedevelopmentandvalidationoftheprocesses
required to assure their performance and technical
viability have themselves have been validated. A
discussionoftheseconceptsfollows.
5 VIRTUALEATON
LIFECYCLE
CONSIDERATIONS
There isadualresponsibilityfor the ultimate safety
and efficiency of vessel traffic and protection of the
environment by competent national authority. A
simplifiedflowoftasksperformedbyeachauthority
is illustrated in figure 2. The first responsibility
involves performing hydrographic surveys to
determine the configuration
of waterways and the
developmentofnauticalchartsthataccuratelyportray
survey results. The second responsibility has to do
with the design, provisioning and maintenance of
AtoNsystemsbaseduponthesesurveys.Historically
under normal circumstances these authorities
performtheirtasksaccuratelyandefficiently.
Figure2. Virtual eAtoN life cycle representing roles of
nationalhydrographicandAtoNauthorities.
However,therapidexpansionofvesselnavigation
in the Arctic has exposed deficiencies of existing
capabilities to perform hydrographic surveys,
produce updated nautical charts and design AtoN
systems to keep pace with this expansion. For
exampletheoriginalNOAAArcticNauticalCharting
Plan published in 2011 proposed the creation of 14
newcharts.Asofthe2015updatetothisplanthreeof
thesechartshavebeenproducedandreleasedforuse
bythepublicwithnodefinitescheduletoproducethe
remaining 11 charts identified in the Plan (NOAA
2015).
There are many ways that new technology and
virtual eAtoN
cancontribute towards enhancing the
safety of navigation. This includes the gathering of
high resolution, full bottom hydrographic data from
3‐dimentional forward looking sonar (3D‐FLS)
equippedvesselsofopportunitytosupplementscarce
national hydrographic resources to help in eAtoN
positioning. The expansion of capabilities provided
by physical AtoN through
the use of AIS eAtoN
technologycanalsobefurtheracceleratedthroughthe
deploymentofvirtualeAtoNinareasnotsuitablefor
physical AtoN or AIS eAtoN. This would also
embraceneweAtoN conceptssuchasthedisplay of
recenttransitsbyicebreakerswithinasettimeframe
as well
as the real time detection of hazards to
navigationfordisplayonECDISonamomentaryor
transientbasiswhilethehazardexists.Discussionof
these concepts in terms of the AtoN development
lifecycleisprovidedintheparagraphsthatfollow.
291
5.1 EstablishmentofRequirements
Determination of requirements for traditional AtoN,
AIS eAtoN and virtual eAtoN is based jointly upon
the results of hydrographic surveys and the needs
associated with vessel navigation. The factors
comprising each of these needs are assessed by
different independent organizations according to
different regulations. Coordination and
cooperation
between national authorities for hydrography and
buoyageisessentialtoeffectcomprehensivenational
systems. Adequate representation and participation
by national representatives in activities and
committees of the International Hydrographic
Organization (IHO) and International Maritime
Organization (IMO) can help ensure effective
implementation and compliance with international
standards.
5.1.1 5.1.1 Hydrographic
Survey
Decisions regarding the performance of
hydrographic surveys are made by competent
national authority based upon guidance provided
through the IHO concerning how hydrographic
surveysareperformed,theproductsofthesesurveys
and the methods by which survey and AtoN
information is depicted in nautical charts. For the
purposes of this
discussion reference is made to
shallowwatersurveysinareasoflessthan100meters
in depth in accordance with IHO Standards for
Hydrographic Surveys (IHO SP44). Specifically, this
refers to Order 1a surveys intended for harbors,
harbor approach channels, recommended tracks,
inland navigation channels and coastal areas with
high
commercial traffic density. Many hydrographic
survey projects require the use of multibeam
echosounders capable of obtaining hundreds more
soundings per unit time than single‐beam systems
and cover a wide swath of the sea floor. Other
methodsincludetheuseofsidescansonarsystemsto
assist in detecting objects that
project from the sea
floor. Both of these systems provide nearly 100
percent bottom coverage of the sea floor, greatly
enhancingtheabilitytodetecthazardsundiscovered
bylessmodernsurveys.
An alternative form of multibeam sonar that
appears suitable for hydrographic survey is 3D‐FLS.
Somesystemsarecapable
ofscanningwideswathsof
theseafloorwithupto100percentcoverage.Rather
thanbeingaimedathwartshipsatrightanglestothe
pathoftransit,3D‐FLSisaimeddirectlyaheadofthe
vessel and is used as a navigation sonar to avoid
vessel grounding on uncharted shoals and
to detect
hazardstonavigationthatresidebelowthewaterline
both attached to the bottom and floating within the
watercolumn.Witharangeofupto1,000meters,a
60 degree conic projection and vertical range to
depths of up to 50 meters, widespread use of such
equipment by
vessels in uncharted regions such as
the Arctic and sharing of this data through
independentsourcingcouldwellsupplementnational
hydrographic survey resources in these areas.
Althoughresearch into theuseof this technology to
supplement surveys is in the earlier stages and
generallyrelatedtoautonomousunderwatervehicles
(see i.a.
Zhang et al, 2008 and Suman et. al, 2015);
Wright and Zimmerman (2015) determined that full
seafloorswathdataobtainedusing3D‐FLSisuseful
for nautical chart development and virtual eAtoN
placement. The availability of detailed hydrographic
sensordatathroughanyoralloftheseresourcesisa
first step towards determining locations suitable for
establishing waterways regardless of whether
traditionalAtoNoreAtoNareintendedforuse.
5.1.2 AtoNRequirements
The identification of AtoN requirements is based
uponthecombinationofhydrographicsurveyresults
and the needs of vessel navigation. The main
objectives to be achieved in defining
requirements
include assisting navigators in identifying their
position,determiningasaferouteoftransit,warning
ofdangersandobstructions,promotingthe safeand
economicmovementofcommercialvesseltrafficand
the safe and efficient movement of military vessel
trafficandcargoofstrategicmilitaryimportance.This
includes reasonsforrejecting
other obvious or more
economical solutions to the problem that might be
indicated from an examination of the relevant
nautical chart such as, for example, physical AtoN
and AIS eAtoN. As much as practical, AtoN are
establishedwithintheconfinesofthelateralsystemto
markchannelsandotherareasof
safewateraswellas
hazards to navigation and wrecks (USCG 2005b,
2005c).
Theprocessusedtodefinerequirementsinterms
ofinitialjustificationbaseduponuserneeds,benefits
accruedandthecosttoachievethesebenefitsremains
unchanged.Justificationisaccomplishedonasiteby
site basis, and general
guidance for accomplishing
thisforvirtualeAtoNisprovidedlaterinthetextin
thediscussionondesign.However,theavailabilityto
use virtual eAtoN as an option to fulfill AtoN
requirements becomes apparent as new capabilities
are created in previously inaccessible locations.
Characteristicsassociatedwiththeimplementationof
virtual eAtoN
are defined based upon the same
criteriaasfortraditionalAtoN,butmaybemoderated
in terms of guidance and advisories rather than
regulatory requirements. This may be especially
warranted, for example, to reduce or eliminate
warningsfromECDISduetocloseproximitytobuoys
ratherthanreportingpoints.
5.2
Design
ThedesignofvirtualeAtoNsystemsandtheselection
ofindividualelementsthereofisperformedtodefine
the data constructs and types that comprise the
characteristicsofthe digitaldata objectillustratedin
figure1.TheoriginalIALAAtoNapplicationschema
ismodified to incorporate abstraction,encapsulation
and inheritance properties
required to implement
geospatial characteristics that comprise essential
elementsoftheconcept.However,thereisnothingin
this modified schema that is necessarily unique to
virtual eAtoN. Both physical AtoN and AIS eAtoN
can also take advantage of these characteristics to
bolster the automated verification of their watching
properlyand
toobtainthesamebenefitsofimmunity
todisruptionofGNSSandAISservices.Theconcepts
of individual and group virtual eAtoN are also
introduced that enable the inheritance of
292
characteristics of individual virtual eAtoN amongst
the group virtual eAtoN in this system of systems
implementation. The products of design should be
tested using simulations and through emulation of
the processes used in the creation of the design to
determine compliance with and traceability to
requirements and to detect potential
deficiencies in
implementationanduse.
An example of a permanent implementation of
virtual eAtoN is where the individual system
elements (VirtualAtoN) consisting of green and red
lateral marks correctly depict the conventional
directionofbuoyagealongachannel.TheIALAAtoN
Information Product Specification convention is
followedwiththeaddition
oftwonewcharacteristics
one of which points to a geospatial surface
(GM_Surface), curve (GM_Curve) or point
(GM_Point) of the area in the vicinity of the virtual
eAtoN within the ENC. A second characteristic
identifiesalivesingle‐beamechosounderdigitaldata
streamobtainedviaavessel’ssensorbus(e.g.,NMEA
2000 or equivalent) that is compared to the ENC to
provide automatic, real‐time checking of GNSS and
AIS functionality along with verification that the
virtual eAtoN are watching properly. The system
comprising a channel (GroupVirtualAtoN) includes
eachindividual(VirtualAtoN)elementandpointsto
a geospatial surface model (GM_Surface) that
corresponds to the overall group. This group model
exceedsthesumofindividualvirtualeAtoNelements
as it also includes areas of transition, allowing for
seamless verification of each element of the system
andtheentiresystemitself.
An example of a permanent and complex hybrid
system is a traffic separation
scheme (TSS) that
contains AIS eAtoN and virtual eAtoN combined
with communication reporting points along two
distinct transit corridors separated by a boundary
between them. Rather than using green and red
lateralmarks,special purposeTSSbuoyscanbeused
torepresenttheportandstarboardsidesofthetraffic
lanes.However,thesameprocessinaccordancewith
themodifiedIALAAtoNapplicationschemaisused
indefiningeachindividualelementofthesystemand
theentiresystemofsystems.
AnotherexampleofapermanentvirtualeAtoNis
where soundings data along with the boundaries of
theusefuldataaredelineated
usingmultiplespecial
purposemarks inanarea thatcontainssparse orno
soundingsdataatall.Alikelyoriginforsuchdatais
envisionedtobetheresultofindependentlysourced
inputspromulga ted via cognizant national authority
fromavesselof convenienceequipped with 3D‐FLS
capableofproviding
aswathoffullbottomcoverage.
Such data would undergo several stages of quality
checking based upon compliance with product and
processverificationstandardspriortoissuance.
The permanent dynamic marking of coaxial
channels using virtual eAtoN is accomplished
throughtheintroductionofadditionalcharacteristics
that describe vessel draft and speed
in combination
withthegeospatialsurfacemodel(GM_Surface).One
of two or more distinct group virtua l eAtoN
(GroupVirtualAtoN)modelsareselectedinrealtime
based upon assurance of adequate bottom clearance
consideringvessel draft,turningrequirements based
upon vessel speed and momentum, and other
relevantcriteria.
Amuchsimplerdesign
ofatemporaryindividual
virtual eAtoN is comprised of a set of curves
(GM_Curve)thatcorrespondtotheboundariesofthe
no‐transit zone. The symbols for no‐entry can be
dynamicallyplacedonECDISanddependentonthe
scale to which the system is set, affecting both the
numberof
symbolsandthedensityinwhichtheyare
displayed.Theactualeffectivetimesfortheareacan
beencodedwithintheENCandupdatedperiodically
asrevisionsbecomeavailable.
TheAIStrackthatcomprisesaportionofavirtual
eAtoN depicting the recent path of an icebreaker is
another example
of a temporary mark. AIS data is
correlated with the ENC geospatial curve model to
create a soundings representation for the track used
with live single‐beam echo sounder data to verify
virtual eAtoN are watching properly and not being
spoofedorinterferedwiththroughtheinterruptionof
AISand/orGNSS
services.Theusefuldurationofthe
track can be determined by cognizant national
authority based upon contemporary observations of
environmental and other conditions and encoded
withintheAISdataand/orthe(VirtualAtoN)feature
itself.
AnewvirtualeAtoNcapabilityisalsointroduced
formarkingtransientormomentarypotentialhazards
to
navigation.Availableonlyasaresultofenhanced
situationalawarenessoftheunderwaterenvironment
madepossibleusing3D‐FLS,theserepresenthazards
affixed to the bottom that include reefs and ledges,
andhazardspresentwithinthewatercolumnsuchas
growlers, shipping containers and whales. An
exampleiswhereoneor
moreIsolatedDangermarks
aredisplayedonECDISatpositionsthatcorrespond
tothehazardlocations.Asimilarcapabilityusing3D‐
FLS is already integrated into many existing ECDIS
installations via a vessel’s sensor bus network, but
this must be further refined in terms of display
features,symbolsandoperator
trainingtobecomean
effectivemeansofalertingwatchstanderstorealtime
hazardstonavigation.
5.3 Implementation
Once the AtoN requirements and design tasks have
beencompleted,theproductsofthese tasksmust be
forwarded to cognizant authority for inclusion into
nauticalcharts.Thisisaccomplishedinparallel with
preparing to
deploy virtual eAtoN through the
performance of local surveys to confirm positioning
andothertasksasmaybedeemednecessarypriorto
their introduction. In all implementation tasks it is
vital ensure that the processes used during
requirementsdefinitionanddesignensurethecorrect
virtual eAtoN aid is created and
translates into a
properimplementationoftheaid.
Feasibility of the approach is enhanced through
the identification of challenges encountered during
development and testi ng, the implementation of
contingency plans in recognition of these potential
challenges, and maximizing possible opportunities
thatresultthroughoutthedevelopmentlifecycle.An
example of such a
challenge includes the
293
identification of differences between the conditions
representedbythemostrecentsurvey,whichmaybe
years out of date, and present‐day conditions that
reflectadifferentbottomconfigurationasaresultof
stormactivityandbottomshifting duetocurrents.
Achievability is heightened through the
identification and management of
significant risk
elements throughout the development process.
Metrics are needed to determine development
progress and overall system effectiveness. This is
accomplished by continually reassessing the virtual
eAtoNimplementationplananddeviationfromplan
for resource use (human, facilities, etc.) and risk
assessment in terms of task achievement, effort
indicators and
milestone fulfillment. Requirement
and design modification processes need to be
established along with tracking of changes needed
throughoutdevelopmenttofacilitatemetricreporting
of requirement, design and implementation of both
ENC and virtual eAtoN. Metrics focusing on risk
assessment of the quality and structure of the
schedule, work breakdown structure consistency,
critical path analysis and the identification of high
risk activities and events, and risk mitigation
scenariosshouldalsobeidentified.
Thesystemiscompletewhenallstepsnecessaryto
implement the virtual eAtoN system have been
identified and metrics established to ensure
measurable progress indicates completion. This
approach will ensure
virtual eAtoN feature and
capability traceability to product specification and
design, system configuration stability, adequacy of
testing,andoverallsystemmaturity.
5.4 Verification
The same processes and procedures used to verify
physical AtoN and AIS eAtoN characteristics in
determining they are watching properly can be
applied to virtual eAtoN. However, additional
procedures are required in verifying virtual eAtoN
acrossthreelevelsthatinclude:
Dataobject,
Technicalperformance,and
Physicalcharacteristics
Data object verification involves a continuous
process used by cognizant authorities and service
providers to examine AtoN‐related data across
multiple databases to detect errors and
inconsistencies inherent
to database operations as
wellashackingandinfiltration.Verificationofvirtual
eAtoNtechnicalperformancefocusesondetermining
that the system is operational and performs the
required functions. Verification of physical
characteristics for establishing and verifying virtual
eAtoNisbaseduponreferencestofeaturesthatexist
withinthelocalenvironment.
Further
insight into verifying physical
characteristicsofvirtualeAtoNwasdemonstratedby
theauthorsinexperimentsundernominalconditions
aswellaswhenprecisepositioninginformationthat
should normally be available using GNSS, AIS and
other sources was unavailable due to a variety of
manmade and natural events (Wright and Baldauf
2015).Undernominalconditionsexperimentalresults
indicated that live sensor measurements coincided
with expectations in terms of local physical
environmental features represented by a geospatial
surface model of ENC soundings and echosounder
depthsindicatingahighlevelofconfidenceofproper
positioning. Under conditions simulating GNSS/AIS
unavailability, denial of service and
spoofing,
discrepancies were found between vessel position
sensor measurements and local physical
environmentalfeaturesthatprovidedahigh levelof
confidencethatvirtualeAtoNcouldnotbeverifiedas
watching properly. Environmental feature
discrepancies were also identified as well as
differences between depths represented by ENC
soundings and depths reported
by the echosounder
after compensating for tide levels, hull depth and
transducer offset. Differences were also detected
between the bottom slope derived from ENC
soundings and bottom slope derived from
echosounder readings. An additional measure was
examinedwheresignificantdifferencesweredetected
between the rates of change of the bottom slope
derivedfromtheechosounderreadingsascompared
totheENC.Anexampleofthisprocessisprovidedin
paragraph7ofthetext.
5.5 Maintenance
The use of independently sourced 3D‐FLS data
obtained from vessels of opportunity can provide
significantadvantagestotheupdateandmaintenance
of all AtoN
(physical, AIS and virtual) as well as
nautical charts on a continual basis, and can
supplement existing hydrographic survey resources.
No significant differences are anticipated in the
maintenance of databases and the installation and
operation of virtua l eAtoN beyond the normal
evolutionandenhancementofthemethods,processes
and procedures already
established by cognizant
nationalauthorityforphysicalAtoNandAISeAtoN.
6 LIMITATIONSANDVULERABILITIES
Potential limitations and vulnerabilities associated
with the implementation of eAtoN technology exist,
some of which are described below. With careful
planning and diligent design and implementation
practices these limitations may be managed and
overcome to
ensure their reliable and verifiable
operationisachieved.
6.1 AISBroadcastRange
The range of AIS broadcasts in the VHF Frequency
spectrum is limited to line of sight based primarily
uponthe heightofthe basestationtransmitting and
vesselreceivingantennae.TherangeofVHFsignalsis
estimatedatnominally
20miles atsea(USCG 2015).
This limits the placement of AIS eAtoN to achieve
reliableperformanceatotherthanremotelocationsto
a distance of less than 20 miles, especially inland
where terrain and ground‐based structures can
interferewithsignalpropagation(Baldauf2008).
294
AIS is also subject to the effects of Tropospheric
ductingthatcanpropagateVHFsignalshundredsof
miles from their origin (Biancomano 1998). Such
effects can introduce interference sources to signals
from AIS stations within the nominal AIS reception
rangeandcanresultinperformancereductionofAIS
bothashore
andonvessels(ITU2007).
6.2 AISSpoofingandJamming
The ability to spoof and jam AIS broadcasts has
particular significance where AIS eAtoN signals are
usedforvesselnavigation.Alackofsecuritycontrols
can facilitate a ship being diverted off course by
placing eAtoN in undesirable or even
dangerous
locations inadvertently, for hijacking or for other
nefariouspurposes(Simonite2013).
ThevulnerabilitiesofAIShavealsoresultedinits
use by criminals to an attempt to evade law
enforcement(Middleton2014).Anotherreportfound
that AIS data is being increasingly manipulated by
ships that seek to conceal their identity,
location or
destination for economic gain or to sail under the
security radar, and concludes that this is a fast
growing, global trend undermining decision makers
who rely, unknowingly and unwittingly, on
inaccurate and increasingly manipula ted data
(Windward2014).
6.3 GNSSSpoofingandJamming
Similar to AIS, Global Navigation Satellite System
(GNSS) signals can also be spoofed and jammed
causing unreliable and even deceptive navigation
signalstobereceivedbyvessels(ForssellB.2009).A
recent example is an experiment by a group of
University of Texas at Austin researchers where a
yacht was driven well off course and essentially
hijacked using spoofing techniques (Zaragoza 2013).
This phenomena was also the subject of a recent
article in the US Coast Guard Proceedings
acknowledging this as being of concern beyond the
maritimeindustrytoincludethetransportationsector
asa whole(Thompson 2014).Jammingcan havethe
same effects as an outage,
as was demonstrated in
2010 when numerous, low power personal privacy
jammers were detected as interfering with GPS
involving airport operations at Newark, NJ
(Grabowski2012).
6.4 GNSSOutages
The worldwide GNSS is comprised of the United
StatesGPS,RussianGLONASS,EuropeanGalileoand
ChineseBeiDousystemswhichare at
variousstages
of completion. These multiple systems imply that
backup capabilities exist if one or more of these
systemsweretogooutofservice,eithertemporarily
or on a permanent basis. This was demonstrated
duringtheten‐hour GLONASSoutagethatoccurred
on 1 April 2014 where a Broadcom 47531
receiver
performing the simultaneous tracking of GPS,
GLONASS, QZSS and BeiDou signals was able to
successfullyidentifyandremove thebadGLONASS
satellite positions (Gibbons 2014). Multiple GNSS
receivers are only beginning to come into the
commercial marketplace. Under normal conditions
theperformanceofthesesystemsislikelytoequal
or
exceedexisting,singletechnologysystems.
All GNSS regardless of technology used are
subject to the same atmospheric and signal
propagationlimitations,multipathinterference, orbit
errors,satellitegeometryandorbitaldebris.Oneora
combination of such factors may degrade GNSS
signalstoreducetheiraccuracyormaketheirsignals
unreliable
or unusable. With the discontinuance of
Loran and no commitment to establish any backup
system to GNSS using a fundamentally different
positioningtechnology such as that used by eLoran,
there is presently no alternative available for
navigation other than that provided by traditional
aids to navigation. The georeferencing of eAtoN
to
bottomfeaturesmayhelptoreducetheoveralleffect
ofGNSSoutages.
6.5 DatabaseHacking
One of the greatest vulnerabilities of eAtoN is their
primary existence as data objects in cyberspace,
without having a traditional physical presence to
provide backup in the event of their electronic
corruption or disappearance. This
property makes
them susceptible to hacking and denial of service
attacks that can render them useless or even
detrimentalandhazardoustonavigation.
Widespread corruption can occur at the source
databases within which eAtoN objects reside at the
authorizedserviceprovider.IntheUnitedStates this
responsibilityissharedbetween
theCoastGuardfor
AtoN and the Light List, and NOAA for ENC that
form the nation’s navigation charts. Corruption can
also occur at the local level, where individual or
groupsofeAtoNinthesamegeographicalareamay
becorrupted.
Initiatives exist at both the Coast Guard and
NOAAaimed
atdefendingtheircomputer networks
from attacks (Radgowski 2014; NOAA 2014). Both
initiativesacknowledge the threats involvedand are
steps in the correct direction to manage and even
overcome the adverse effects on national security
imposedbythesethreats.IssuesthatpertaintoeAtoN
design, development and implementation cross
agency
lines, barriers and firewalls; making the
solutiontotheseproblemsevenmoredifficult.
7 METHODSFORVERIFICATION
TherearethreelevelsatwhichverificationofeAtoN
mustbeconsidered.Thefirstlevelfocusesonwhere
theyarerepresentedinelectronicformasdataobjects.
Numerous vulnerabilities can exist ranging from
simple
data entry errors to the intentional hacking,
manipulation or destruction of the data content.
Compounding the severity of the problem is that
eAtoN data is represented in multiple data systems
across Government agencies that may be altered or
modifiedfromtheiroriginalcontent,makingtheENC
aproductofcollaborative
datasets.
295
The second level of verification is the actual
technical performance of the eAtoN device and
mechanisms themselves. The third level involves
verification of the physical eAtoN characteristics as
manifestatthedeployedlocationonECDIS.
7.1 DataObject
A data object defined as an item or group of items,
regardless
of type or format that a computer can
address or manipulate as a single object implies
characteristics contained within the database are
highly correlated with the unique eAtoN object it
represents. The corruption of these data can
fundamentallyalterthebehavior,functionalityand/or
performance of eAtoN. Such corruption can occur
throughout the lifecycle of the object from the
characterizationofdataasrequirements,designofthe
structure in which these data reside, initial entry of
thedataintothedatastructure,processofextracting
thedata,itsfusionwithotherdatatoeffectaprocess
oroutcomeusinganavigationaldisplay,
andthefinal
representation of the data in its intended use for
navigation.
The process flow depicted in figure 3 provides a
simplified example of a generic verification process
thatcouldbeusedonacontinuousbasisbycognizant
service provider(s) to examine the contents of
multiple databases to detect
errors and
inconsistenciescausedbydatabasehackingaswellas
errorsinherenttodatabaseoperations.Thisapproach
is conceptually aligned with the United States
Department of Homeland Security Continuous
DiagnosticsandMitigation(CDM)Programdesigned
toprotectgovernmentnetworksandtheirdata.
7.1.1 DatabaseStructures
Multipledatabasesanddatastructuresdistributed
geographically across different government agencies
host the data required to create, implement and
support eAtoN operations. These include legacy
systems already supporting AtoN characteristics
modified to support eAtoN and the equivalent data
requirementswithinthe ENC, with legacy processes
used to integrate these data and create their final
products.The
implementationandhostingofeAtoN
datarepresentationsexistsondifferentdataplatforms
andhostsoftware,withdiverseformatsandtimingof
system updating and maintenance. How these data
and relevant metadata are shared, the flow of these
data managed, and the processes and frequency
through which this occurs is the focus
of the
Committee on the Marine Transportation System
(CMTS), a Federal interagency coordinating
committee in the United States. This should be
accomplished in a manner that coincides with the
updateandrevisioncyclesofthecontentsofthedata
structures independent of the development of
products derived from the data
contents. This also
requires proper filtering and assurance that the
destination system and associated processes be
sufficientlyrobustsoasnottobeoverwhelmedbythe
volumeofdatareceived.
Figure3.eAtoNDataObjectVerificationProcess.
7.1.2 DataNormalization
Prior to initiating data object verification it is
necessary that the contents of the data streams be
processed and normalized from their native formats
contained within the source databases to a common
formatensuringpropercomparisonsofthedatamay
be accomplished. This includes data for both AtoN
andeAtoNsincetheyareintegratedtogetherintothe
same legacy systems; ensuring data objects for both
forms are verifiable and can be verified using the
same process. This also requires that inputs of
metadata, human interface and guidance, a priori
data, and other machine data necessary to perform
verification
are prioritized and properly associated
withthedataforsubsequentprocessing.
The product of the data normalization stage
represents the totality of the data from all sources
necessarytoaccomplishverification:
DE
eAtoN(n)={DeAtoN(n),EeAtoN(n)} (1)
296
whereD=AtoN/eAtoN;andE=ENCdataobjects.Note
thattheprocessflowoffigure3hasbeensimplifiedto
show eAtoN data, however both AtoN and eAtoN
data objects from the same data sources can be
verified using this same technique. These data are
provided at a rate sufficient to process
changes in
synchronization with the data at their source
databases.
7.1.3 VerificationProcess
Verificationofnormalizeddataisaccomplishedwith
theknowledgeofchangesthataresupposedtohave
occurredand theimplication thatany other changes
thatmaybedetectedarethereforediscrepancies.Each
individual normalized AtoN/eAtoN data object
is
comparedtothechangelisttodeterminewhetheritis
containedwithinthesetofchangesexpectedforthat
specificindividualprocess:
DE
eAtoN(n)∈{DEeAtoN(Δ)} (2)
Ifthedataobjectispartofthesetofchangesthen
the characteristics of the normalized data object are
comparedtothoseontheChangeListtoensuretheir
properimplementation:
DE
eAtoN(n)=DEeAtoN(nΔ) (3)
whereanaffirmativeresultcausesadeterminationof
the AtoN/eAtoN as a verified data object and a
negativeresultcausesadeterminationofadataobject
discrepancy.
Ifthedataobjectisnotpartofthesetofchanges
thenthecharacteristicsofthenormalizeddataobject
arecompared
tothoseofthepreviousrevision(n′)of
thedataobject:
DE
eAtoN(n)=DEeAtoN(n′) (4)
whereanaffirmativeresultcausesadeterminationof
the AtoN/eAtoN as a verified data object and a
negativeresultcausesadeterminationofadataobject
discrepancy.
Completionofindividualdataobjectverificationis
achieved with a determination of verified or
discrepancy,whereinmetricsaregeneratedfollowed
bythe
examinationofthenextdataobject:
DE
eAtoN(n)→MetriceAtoN(n) (5)
DE
eAtoN(n)=DEeAtoN(n+1) (6)
Upondetectionofthelastdataobject,dataobject
verification for this process run is completed and
initiation of Technical Performance is then followed
byPhysicalCharacteristicsverification.
7.1.4 Metrics
Data object examination is complete when steps
necessary to determine verifica tion or discrepancy
have been achieved. Metrics to measure
verification
progress andresultantproducts mustbe established
to indicate process completion and performance
scores are created to indicate product quality and
deficiency levels. Such metrics must also ensure
feature and capability traceability to product
specification and design, stability of software
configuration, adequacy of depth and breadth of
testing, and overall
product maturity. Configuration
controlsandtroublereportingproceduresneedtobe
established to track the rate, type and severity of
discrepanciesaswellasrequiredchangestosoftware,
processes, design, and requirements resulting from
discrepanciesfoundandcorrected.
7.2 TechnicalPerformance
Verification of the technical performance of AIS
eAtoNlies
primarilyindeterminingthatthesystemis
operational and performs the required functions.
Generalguidanceonthissubjectmaybefoundinthe
appropriate IALA guidelines (IALA G1028).
GuidanceonverificationofAISequipmentshouldbe
found in the technical specifications, acceptance test
procedures and maintenance test procedures
appropriateforspecific
equipmentconfigurations.
7.3 PhysicalCharacteristics
TheexistenceofeAtoNasdataobjectswithouthaving
a traditional physical presence does not necessarily
preclude their verification using many of the same
physical parameters as AtoN. This may provide an
ideal opportunity to demonstrate the use of
technologytoresolvedoubtsandconcerns
regarding
navigation strictly by electronic means rather than
traditional methods by using live environmental
sensor data to obtain fixes to known landmarks,
structures,bottomterrainfeaturesandbuoys.
Many of the physical characteristics of physical
and synthetic AIS eAtoN are shared with their
associated AtoN. Characteristics unique to physical,
synthetic and
virtual eAtoN include type, position
andoperational statusas well asthe presentation of
these characteristics on navigational displays, e.g.,
radar and ENC/ECDIS. The highest priority is
depictionofposition,whichiscloselyfollowedbythe
othercharacteristics.
7.3.1 Position
Theeasiestandmostriskymeansofverifyingthe
eAtoN
characteristic associated with position is
though the use of GNSS to compare the measured
position with the charted position. In the case of
physicalandsyntheticeAtoNthereisaphysicalAtoN
present at the location as well as an AIS/ECDIS
representationtocorroboratetheGNSSfix,assuming
that verification of
AtoN position has already been
accomplished. Prudence would dictate that bearings
to physical landmarks and features be also made to
furtherconfirmthereliabilityofthefix.
ForAISand non‐AIS virtua l eAtoN, the problem
becomesmorecomplicatedsincethereisnophysical
AtoN presence at all. A fix
developed based upon
bearings taken to physical landmarks and features
would be a suitable method for verifying location
297
onlyinthecasewheresuchfeatureswerevisibleand
not obscured or out of visual or radar range.
However, there is another means to take such a fix
through reference to ground. This may be
accomplished, again using modern technology,
throughverificationusingknownsurfacelandmarks
(radar bearings to
known landmarks, etc.). This can
include bottom features obtained through wireform
and/orpointcloudENCmodelscomparedtolive3D‐
FLS and/or echosounder measurements made over
timeintervalsusingrunningaveragesandderivative
trend information. ENC information is already on
boardvesselsinthechartingequipment(e.g.,ECDIS)
andrequires
theproperresolutionandcorrelationto
determinebearings,produce the necessary fixes and
generate warnings. Such capabilities are possible
through the use of the IHO S‐100 Universal
Hydrographic Data Model that supports a wider
variety of hydrographic‐related digital data sources
and products than the IHO S‐57 IHO Transfer
StandardforDigitalHydrographicData.Specifically,
thisincludesnewspatialmodelstosupportimagery
and gridded data, 3‐D and time‐varying data, and
new applications beyond those of traditional
hydrography.
Fix and bearing information to known physical
environmentalfeatures for eacheAtoN can be taken
during initial installation and
encoded as part of its
characteristics.Thesecharacteristicscanthenbeused
anytimethereaftertoverifypositionaccuracyduring
normal use and subsequent verification. Data
encryptionofpositioncharacteristicscanalsobeused
toensuretheirsecurityandvalidity.
Suchmethodscanalsobeusedtodetecttheeffects
of AIS
and GNSS jamming and spoofing since the
presumedlocationbaseduponGNSSislikelytonot
coincide with environmental features. Used with
inertial backup, it would also be possible to verify
positionintheeventofGNSSoutage.Dataobtained
from echo sounder measurements using this
techniqueongroundtracks
1,2and3showninfigure
4mayappearsimilartothatshownintable1.
Transit of the intended track (Track 2) is
dependent upon accurate GNSS position correlation
withchartlocationdata. Shouldeither AISor GNSS
spoofing or jamming occur resulting in inaccurate
positioning,differencesinboth
the depthand/or the
rateofchangeofdepthprofilesbetweentheintended
andactualtransitedcourseswouldbedetectable.For
example, should spoofing occur where the vessel
believes itself to be on the intended Track 2 based
uponAIS/GNSSsensorreadingsyetfollowseitherof
errorTracks1or
3,deviationfromthepropercourse
will be detected through comparison of derived
bottomfeatureandcontourdataillustratedintable1
with independently obtained echo sounder readings
even though AIS and/or ECDIS is falsely displaying
theintendedcourse.ShouldGNSSjammingoroutage
beencountered,thesesamebottomreferencedata
can
be used with inertial system backup to continue
navigationandaccuratelyupdatethevesselsposition.
* Track 1 + Track 2 # Track 3
Figure4.DivergentGroundTracks1and3Comparedtothe
intendedGroundTrack2.
Table 1. Difference and Rates of Change of Error Track 1
andErrorTrack3fromIntendedTrack2showninFigure2.
7.3.2 OtherCharacteristics
Once verification of accurate eAtoN positioning
has been accomplished, verification of additional
characteristics that include eAtoN type, name, etc.,
wouldbeperformedbyexaminingthecontentsofthe
AIS/ECDISinformationonthenavigationdisplay.For
example,thetypeindicationshouldcorrelatewiththe
proper valid symbol for
cardinal marks (N/E/S/W),
lateralmarks(IALAA/Bportandstarboard),isolated
danger, safe water, special purpose or emergency
wreckma rkingaspublishedforthatlocation.eAtoN
name and other characteristic verification would be
accomplishedusingthesamemethod.
298
7.3.3 Metrics
Physical characteristic examination is complete
whenallstepsnecessarytodetermineverificationor
discrepancy have been accomplished. Metric results
providetraceabilityofverificationandidentifyareas
where further product and process maturation is
needed.Datacollectionformanymetricscanalsobe
automated, ensuring measurable progress in
completing
verification and generating performance
scorestoaidintheirunderstanding.
8 PRESENTSTAGEOFMATURITY
eAtoNtechnologyis very much in an early stage of
development with only a handful of AIS virtual
eAtoNdeployedinexperimentalevaluationprogram
locations worldwide. Non‐AIS virtual eAtoN
configurations are even less mature
as theoretical
conceptsandimplementationshaveyettomaterialize
outside the laboratory. Participation of the maritime
community is being actively solicited by cognizant
authoritiesandauthorizedserviceproviderstoensure
progressisconstructiveandmeetinguserneeds.This
is evidenced by U.S. Army Corps of Engineers
(USACE), NOAA, and Coast Guard
invitations to
maritime stakeholders to participate in Future of
NavigationPublicListeningSessionsandNavigation
Information Days throughout the country to collect
comments and feedback regarding requirements for
navigationalinformationandservicedeliverysystem
needs (Smith 2014; NOAA 2014a). Additional AIS
eAtoN installations are being deployed throughout
theUnitedStates
inanattempttofulfillawidersetof
maritimeneeds.
9 CONCLUSIONS
Installation of AIS‐based eAtoN system facilities are
continuing as operational experience and results
showingtheirutilityaredocumented. Acriticalneed
exists for non‐AIS eAtoN technology for use in
remote and sensitive environments as described.
Further
research and development should be
encouragedinthisarea.
Significant limitations and vulnerabilities exist in
the AIS and GNSS technologies that support eAtoN
operations.Spoofinganddenialofserviceattackswill
accelerateduetothelackofsecurityinbothofthese
areas as states and criminal organizations gain
experience
inusingandmisusingthesetechnologies.
Opportunities exist using currently available data
fusion and sensor technology to mitigate these
problems and reduce the severity of and even
eliminate their effects, increasing marine safety in
generalandspecificallythesafetyofnavigation.The
techniques proposed for verification of eAtoN can
alsobe
appliedtoimproveandautomateportionsof
existing verification practices for all AtoN: physical,
AISandvirtual.
Potential also exists for expanding IMO e‐
Navigationcapabilitiesthroughintegrationof3D‐FLS
technology as a means for enhancing the safety of
navigation.Oneaspectofthisisthat thePolarCode
should be amended to mandate 3D‐FLS as an echo‐
soundingdevice having forward‐looking capabilities
as a vessel carriage requirement in the Arctic.
Alternatively, 3D‐FLS should qualify as one of the
two already required independent echo‐sounding
devices.
ACKNOWLEDGEMENTS
Theopinionsexpressedaresolelythoseoftheauthors
and
do not representtheofficial positions of the US
Coast Guard, National Oceanographic and
Atmospheric Administration, International Maritime
Organization, International Hydrographic
Organizationoranyotherorganization.
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