23
1 INTRODUCTION
Themaritimesectorwasoneofthefirstcommunities
that recognized and exploited the opportunities and
advantages provided by GNSS systems. In fact, the
introductionofGNSSrepresented agreat revolution
inthemaritimefield.
GNSS positioning has progressively acquired
moreandmorerelevanceinallshipssailing around
theglobe.Atthebeginning,GNSSwasonlyusedasa
way to know the current position, but toda
y GNSS
receivers are connected and integrated with other
differentfunctionssuchasIntegratedBridgeSystems,
ECDIS,ARPA,GMDSS,AIS,LRITorVDR.
It is recognised that Global Navigation Satellite
Systems (GNSS)havebecome the prima
ry means of
obtaining Position, Navigation and Timing (PNT)
information at sea. Most of the ships in the world
(even in the recreational and leisure field) are
equipped with GNSS receivers (SOLAS carriage
requirement). And nowadays these users take
advantageofdifferentaugmentationsystemssuchas
DGNSS or SBAS/EGNOS, as they provide an
adequat
eanswer,especiallyintermsofaccuracyand
integrity.
Thequestionis:howmanyoftheGNSSonboard
equipmentareSBASready?Toanswerthisquestion,
thispaperpresentstheresultsofthesurveythathas
been done among a large set of approved maritime
devicesincludingaGNSSreceiver.
1.1 WhatisEGNOS?
Sat
ellitenavigationsystemsaredesignedtoprovidea
positioningandtimingserviceovervastgeographical
areas (typically continental or global coverage) with
high accuracy performance. However, a number of
SBAS/EGNOS Enabled Devices in Maritime
M.López
GSA,EuropeanGlobalNavigationSatelliteSystemsAgency,Prague,CzechRepublic
V.Antón
ESSP,EuropeanSatelliteServicesProvider,Madrid,Spain
ABSTRACT:Nowadays,itisafactthatGlobalNavigationSatelliteSystems(GNSS)havebecometheprimary
meansofobtainingPosition, NavigationandTiming(PNT)informationatsea.Mostoftheshipsintheworld
are equipped with GNSS receivers. And currently these users take adv
antage of different augmentation
systemssuchasDGNSSorSBAS/EGNOS,astheyprovideanadequateanswer,especiallyintermsofaccuracy
andintegrity.
To take advantage of this improved accuracy, direct access to EGNOS in vessels can be achieved through
EGNOSenablednavigationreceiversandEGNOSenabledAIStransponders.Therefore,thenaturalquest
ion
is:ArethoseGNSSreceiversSBAS(EGNOS)enabled?Inmostcasestheyare;SBASisbeingused.Thispaper
provides an analysis of the number of onboard devices, mainly devoted to navigation purposes and AIS
transponders,whichareSBAScompatible.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 12
Number 1
March 2018
DOI:10.12716/1001.12.01.01
24
eventsmayleadtopositioningerrors.SatelliteBased
Augmentation Systems (SBAS) are designed to
augment the navigation system constellations by
broadcasting additional signals from geostationary
(GEO) satellites. EGNOS (European Geostationary
Navigation Overlay Service) is the European SBAS
providing an augmentation service to the Global
PositioningSystem(GPS).
EGNOShasbeen
designedtobroadcastaGPSlike
rangingsignalinEuropewithembeddedcorrections,
providing improved performances over GPS. With
EGNOS, all navigation receivers will benefit from
enhanced accuracy, availability and continuity over
GPS.
TheEGNOScoverageareaisWesternEurope,but
could be readily extended to include other regions
within
the broadcast area of the geostationary
satellites,such asAfrica. EGNOSisthefirstelement
of the European satellitenavigation strategy and a
major steppingstone towards Galileo, Europeʹs own
globalsatellitenavigationsystemforthefuture.
In addition to EGNOS, there are other SBAS
around the world with similar
characteristics and
compatible among them. Figure 1 presents the
coverageofthedifferentSBASsystemsintheworld.
Figure1.ExistingandplannedSBASsystems
The main objective of the EGNOS Open Service
(EGNOSOS)istoimprovetheachievablepositioning
accuracybycorrectingseveralerrorsourcesaffecting
theGPSsignals.Thecorrectionsfreelytransmittedby
EGNOSgeostationarysatellitescontributetomitigate
the ranging error sources related to satellite clocks,
satellitepositionandionosphericeffects.The
EGNOS
OS minimum accuracy is specified in the following
table[1].
Table1.EGNOSOSHorizontalandVerticalAccuracy
_______________________________________________
Accuracy DefinitionValue
_______________________________________________
Horizontal Correspondstoa95%confidence 3m
boundofthe2dimensionalposition
errorinthehorizontallocalplanefor
theWorstUserLocation
Vertical Correspondstoa95%confidence 4m
boundofthe1dimensionalunsigned
positionerrorinthelocalverticalaxis
fortheWorstUser
Location
_______________________________________________
Accuracy Definition Value
2 ONBOARDGNSSRECEIVERS‐SOLAS
CONVENTION
To have a picture of what kind of navigation
equipment can be found onboard vessels, SOLAS
Convention [2] must be consulted. The SOLAS
Conventionisconsideredasthemostimportantofall
international treaties concerning the safety of
merchantships.ChapterVwithinSOLAS
Convention
deals with safety of navigation; it identifies
navigationsafetyserviceswhichshouldbeprovided
byContracting Governmentsand sets forth
operational provisions applicable in general to all
shipsonallvoyages.OfspecialinterestisRegulation
19 within chapter V, which establishes the carriage
requirementsforshipbornenavigationalsystemsand
equipment.
2.1 SatelliteNavigationEquipment
AccordingtothatRegulation,allshipsirrespectiveof
size are required to be fitted with a GNSS receiver.
This will probably be a GPS receiver using the US
GlobalPositioningSystemwhichmayormaynotbe
equippedtoprovidedifferentialcorrections,sincethe
carriage
of a DGPS receiver or an SBAS enabled
receiver is not mandatory. The question is: Does a
simpleGPSreceiverfulfiltheIMOrequirementsinall
navigationphases?
Themostcommonsystemusedasprimarymeans
of navigation is GNSS, however currently available
GNSS do not fulfil IMO requirements in regards
to
accuracy and integrity in all the navigation phases.
AccordingtoResolutionA.915(22)[3]onthe“Revised
maritimepolicyandrequirements forafutureGlobal
Navigation Satellite System (GNSS)” GPS (and
GLONASS) has been recognized as a component of
theWorldWideRadionavigationSystem
1
(WWRNS)
for navigational use in waters other than harbour
entrancesandapproachesandrestrictedwaters.That
is,GPSalone,withoutaugmentationisnotenoughin
thesesituations.
A.915(22) recognises that differential corrections
canenhanceaccuracy(inlimitedgeographicareas)to
10 m or less (95%) and also offer external integrity
monitoring. In this sense, this Resolution mentions
the following techniques that can improve the
accuracy and/or integrity of GPS and GLONASS by
augmentation
2
:
Differential correctionsignals fromstationsusing
the appropriate maritime radionavigation
frequency band between 283.5 and 325 kHz for
localaugmentation.
Craftorreceiverautonomousintegritymonitoring.
Integrated receiverscombiningsignals fromGPS,
GLONASS, LORANC and/or Chayka (a Russian

1
InMay2016,theIMOrecognisedalsoGalileoaspartof
theWorldWideRadioNavigationSystem.
2
TotakeintoaccountthatResolutionA.915(22)wasadopt
edon29November2001andconsequentlyitisnotupdat
ed.Someofthesystemshavebeendecommissioned,forin
stanceLORANC,andtechnologicaladvancesarenot
considered.
25
terrestrial radionavigation system, similar to
LORANC).
Wideareaaugmentationsystemsusingdifferential
correction signals from geostationary satellites
suchasEGNOSforEurope,WAASfortheUnited
StatesandMSASforJapan.
Amore recentIMOResolution,A.1046(27)[4]on
the “Worldwide Radionavigation System” refers to
ChapterV of
theSOLAS Convention,Regulation13,
whentalkingaboutnavigationinharbour entrances,
harbourapproaches andcoastal waters.Atthesame
time, IMO Res. 1046 establishes that: where a
radionavigationsystemisusedtoassistinthenavigation
of ships in such waters, the system should provide
positionalinformationwithan
errornotgreaterthan10m
with a probability of 95%. It is important to note that
this is a requirement to be accomplished by the
radionavigationsystem.
The provision of differential corrections,
understood as aids to navigation to be provided by
maritimeauthorities,isnotmandatory.Itisupto
the
Contracting Governments to decide to provide this
servicebasedonthevolumeoftrafficandthedegree