417
1 INTRODUCTION
Introducing of automatic identification system (AIS)
onseagoingvesselschangessignificantlypossibility
of maintaining a proper look‐out, particularly in
restrictedvisibility.Accordingtotherecommendation
oftheResolutionA.1106(29) „Revised guidelines for
the operational use of shipborne automatic
identificationsystems(AIS)”adoptedbyInternational
Maritime Organisation (IMO) on 2 December 2015,
the AIS ma
y be recommended as an anti‐collision
deviceinduetimeanditsintroducinghasnotimpact
on the Rule 19 “Conduct of vessels in restricted
visibility” of the International Regulations for the
Preventing Collision at Sea (COLREG) and its
interpretation. Nevertheless, AIS may be used to
assist in collision av
oidance decision‐making as an
additional source of information which supports
radar and radar tracking aids, by assisting in
[ResolutionA.1106(29)]:
Identification of targets by name, call sign, ship
typeandannavigationalstatus;
Presentationoftargetsheading;
Immediate identification of manoeuvres
performedbyta
rgets;and
Moreaccurate presentation of the targets courses
andspeedsovergroundandrateofturn.
But also, if the target data from AIS and radar
trackingarebothavailableandtheassociationcriteria
(position,motion,etc.)arefulfilledsuchthattheAIS
andradarinformationareconsideredasonephysica
l
target,thenasadefaultconditioninradarequipment,
the AIS target symbol and the alphanumerical AIS
target data should be automatically selected and
displayed[ResolutionMSC,192(79)].
Twobasicparametersneededtoassesstheriskof
collision in meeting situation at sea are passing
distance and passing ti
me called closest point of
approach (CPA) and time to the closest point of
approach (TCPA). AIS calculates their values on the
basis of information on courses over ground and
speeds over ground and the positions of the own
vessel and opposite object, indicated by receivers of
the satellite navigation system (act
ually mainly GPS
orDGPS)connectedtotheonboardAIS.Duetothat
Study Reliability of the Information About the CPA and
TCPA Indicated by the Ship's AIS
R.Wawruch
GdyniaMaritimeUniversity,Gdynia,Poland
ABSTRACT:AccordingtotheIMOrecommendationwhenthetargetdatafromAISandradartrackingareboth
availableandtheassociationcriteriaarefulfilledsuchthattheAISandradarinformationareconsideredasfor
one physical target, then as a default condition in radar equipment, the AIS ta
rget symbol and the
alphanumerical AIS target data should be automatically selected and displayed only. The article presents
researchconductedinrealconditionson thereliabilityofinformationpresented bythe shipʹsAIS aboutthe
passingdistancewiththeothervesselequippedwithAISandtimetopassitbycomparingdatafromtheAIS
withtha
tpresentedbyARPA.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 10
Number 3
September 2016
DOI:10.12716/1001.10.03.06
418
AIS indication should be more accurate and reliable
thanvaluesoftheCPAandTCPAascertainedonthe
basis of radar tracking and presented by automatic
radar plotting aids (ARPA) and automatic tracking
aids (ATA). There are available publications
comparing the accuracy of the position, course and
speed presented by
the AIS and radar plotting aids
[Wawruch 2008]. But it is still an open question the
accuracyandreliabilityofinformationabouttheCPA
and TCPA indicated by AIS as compared with the
accuracy of their values calculated on the basis of
radartracking.
The measurements reported in this article
were
carriedouttofindtheanswertothisquestion.
2 DESCRIPTIONOFTHEMEASUREMENTS
The measurements were carried out in real (not
simulated)conditionsduringtheseavoyagesofships
listed in Table 1 and presented in Figures 1 and 2,
using installed on these vessels AIS and radar
equipment
mentioned in this table too. JRC is the
abbreviation of Japan Radio Company Ltd. Weather
conditionsduring the testsdescribes thestate of the
sea,expressedindegreesoftheDouglasscaleinthe
lastcolumnofTable2.
Table1.Shipsonwhichtestswerecarriedout[Wesłowski
2016,Wilczyński2016]
_______________________________________________
DataMagdalena Pampero
Odendorff
_______________________________________________
Ship’stypeBulkcarrier LPGtanker
GrossTonnage10688446789
Length[m]299.9226,0m
Servicespeed[kn/m/s] 15.6/8,016.7/8,6
Utilisedradarequipment/ JMA‐9132‐SA, JMA‐9172‐SA,
manufacturerJMA‐9122‐ JMA‐9122‐9XA
9XA/JRC /JRC
UtilisedAIS/manufacturerJHS‐183/JRCJHS‐183
/JRC
_______________________________________________
Figure1. Bulk carrier “Magdalena Oldendorff”
[www.google.pl/search?q=magdalena+oldendorff+ship&rlz]
Figure2. LPG carrier “Pampero” [www.vesselfinder.com/
pl/vessels/PAMPERO‐IMO‐9689548‐MMSI‐538006047]
Themeasurementswerecarriedoutfor38meeting
situations with vessels listed in Table 2. The terms
usedinthistablemean:
T‐typeoftheship:
B‐bulkcarrier;
C‐containervessel;
CS‐cargoship;
F‐ferryboat;
FV‐fishingvessel;
P‐passenger
ship;and
T‐tanker;
L‐the length of the vessel presented on the
website;
CPA
mean‐theaveragevalueoftheCPAduringthe
measurement;
MS‐meetingsituation:
1‐overtaking;
2‐head‐onsituation;and
3‐crossingsituation;
S‐sea state expressed in degrees of the Douglas
scale,swmeansswell.
In each test were recorded simultaneously every
30 seconds, indicated
by ARPA and AIS following
parametersoftheobservedvessel:
Bearinganddistance;
Courseandspeed;and
CPAandTCPA.
As the units of distance and speed are officially
used in maritime navigation nautical miles (M) and
knots(kn), andAISandARPApresentvaluesofthe
CPA
andspeedintheseunits.Duetothat,valuesof
CPA and speed are expressed in figures in nautical
miles(M)andknots(kn), andCPA
meanandspeedin
Table2innauticalmilesandkilometresandinknots
andm/s(1M=1852m;1knot=1M/h).
Table2.Observedships[Wesłowski2016,Wilczyński2016]
_______________________________________________
NoNameT L Speed CPAmean MSS
[m] [kn/m/s] [M/km]
_______________________________________________
1 APLVancuver C 328 19.2/9.9 10.1/18.8 2 4
2 BelgianExpress C 180 13.0/6.7 0.7/1.3 1 4
3 BulkSwitzerland B 289 9.5/4.9 17.0/31.5 3 5
4 CapSanMarco C 333 20.0/10.3 2.5/4.7 3 4
5 CarnivalValor P 292 18.2/9.4 2.8/5.2 3 4
6 CarolineMaersk C 347
19.0/9.8 2.9/5.4 1 5
7 ChinaPeace B 289 0/04.4/8.1 1 3
8 CoscoJinggangshanB177 10.0/5.1 3.0/5.5 2 5
9 F.D.GennaroAuriliaB225 12.0/6.2 7.7/14.2 1 3
10FourWindT 249 12.0/6.2 0.9/1.6 3 4
11FreeNeptune CS185 11.5/5.9 9.5/17.6 3 2
12HorncapC 153 14.5/7.5 2.7/5.0 3 3
13HSCB 289 11.6/6.0 5.5/10.1 2 3
14HuaSanT 333 14.0/7.2 3.1/5.8 3 4
15HyundaiUnity C 294 13.3/6.8 9.2/17.0 1 3
16JacamarArrow B 199 14.0/7.2 1.1/2.1 2 5
17JSColumbia B 199 14.4/7.4 5.3/9.8 3
2
18LenaRiverT 290 00.7/1.3 1 2
19MaerskCapeCoastC 249 15.0/7.7 2.1/3.8 2 1
20MountNevis B 290 7.0/3.6 1.7/3.1 2 7
21MSCRachele C 334 19.5/10.0 3.6/6.7 3 5
22NCCDanah T 183 13.5/6.9 2.9/5.4 3 7
23NewHarmony
T 333 14.5/7.4 3.1/5.8 1 6
24NYKAltairC 333 14.1/7.3 6.0/11.1 2 4
25OceanTrader CS180 11.1/5.7 15.7/29.0 1 4
26OOCLKorea C 366 15.8/8.1 1.5/2.7 3sw
27PortShanghai B 190 10.0/5.1 2.2/4.1 2 5
28RegioMarFV21 8.0/4.1 2.4/4.4 1 2
29SamoaB 225 12.0/6.2 2.1/3.9 1 5
30SCLBasilea CS140 14.2/7.3 9.5/17.7 2 3
419
31SouthernNarwhal T 135 13.0/6.7 1.3/2.4 3 4
32SpiritofBritain F 213 23.5/12.1 8.3/15.3 3 3
33StoltPuffinT 100 10.2/5.2 7.4/13.8 1 3
34StoltPuffinT 100 10.2/5.2 5.7/10.6 1 3
35SuezVasilis T 274 14.0/7.2 1.4/2.6 1 4
36TianZhuFeng B
225 10.8/5.6 10.0/18.5 1 7
37UniqueBrilliance B 288 Variable 2.1/3.8 1 6
38VaramoC 166 25.3/13.0 1.3/2.4 2 4
_______________________________________________
Inall cases,observedship wastracked by ARPA
for at least 5 minutes before the start of registration
andbothvessels(ownand opposite)didnot takeat
thistimeanymanoeuvres.Eachseriesconsistedof30
registrations. In 5 meeting situations one vessel was
stayingatanchor:
ownshipinsituationsNo:6,23and
37,observedinsituationsNo:7and18.Inothercases,
duringtheregistration:
Ownshipalteredhercoursewhileobservedvessel
was proceeding with steady course and speed
(situationsNo:20,22and34);
Ownshipwasproceedingwithsteady
courseand
speed and observed vessel altered its course
(situationsNo:10,14,31and33);
Both vessels altered their courses (situation 30);
and
Both vessels were sailing on steady courses and
withsteadyspeeds(situationsNo:1‐5,8,9,11‐13,
15‐17,19,21,22,
24,25‐28,32,35,36and38).
3 DISCUSSIONOFTESTSRESULTS
Described tests were conducted in order to check
whether,whendatafromAISandradartrackingare
bothavailableandtheassociationcriteriaarefulfilled,
the person in command and manoeuvring the ship
(captain or watchkeeping officer) can
rely on values
ofCPAandTCPAofothervesselsavailablefromAIS
only.Theamount of the measurements is small and
makes it impossible to determine any statistical
relationships but allows formulating some general
observations.
TherewereobservedbyAISandtrackedbyARPA
shipsofdifferentsizes,from
thesmallfishingvessel
tolargecontainershipsandtankers,stayingatanchor
and proceeding with different speeds in different
meeting situations and different weather conditions,
including stormy weather, passing own ship at
different CPA, between 0.7 M (1.3 km) and 17.0 M
(31.5km).
Onboard AIS receives, at predetermined time
intervals, the indications of GPS or DGPS receiver,
gyrocompass, speed measuring device and rate of
turn indicator when connected to the unit on the
oppositeship,andknowingtheposition,courseand
speedofownvesselcalculatesCPAandTCPAofthat
opposite ship. Due to that it should detect
and
indicate changes of CPA and TCPA caused by
manoeuvres of the own ship and/or opposite vessel
fasterthanARPAcalculatingcurrentvaluesofthese
two parameters on the basis of the radar detection
and tracking. The tests performed confirmed the
validityofthisview.AsshownintheFigures3,
4,6
and7,inallseriesofmeasurementsduringwhichthe
own and/or opposite ship manoeuvred, AIS pointed
changesintheCPAandTCPAfasterthanARPA.
Figure3.PresentedbyAISandARPAinformationonCPA
of the container vessel “Caroline Maersk” altering course
for 16
o
(situation No 6, own ship at anchor, sea state 5)
[Wesołowski2016]
Figure4.PresentedbyAISandARPAinformationonTCPA
of the container vessel “Caroline Maersk” altering course
for 16
o
(situation No 6, own ship at anchor, sea state 5)
[Wesołowski2016]
Figure5. Presented by AIS and ARPA information on
courseofthecontainervessel“CarolineMaersk”(situation
No6,ownshipatanchor,seastate5)[Wesołowski2016]
Presented in Figures 3 and 4 faster indication of
newvaluesofCPAandTCPAwereachieveddueto
the earlier detection of the opposite ship course
alterationbyAIS thanbyARPA(Figure5).
420
Figure6.PresentedbyAISandARPAinformationonCPA
of the tanker “New Harmony” altering twice its course
(situation No 23, own ship at anchor, sea state 6)
[Wesołowski2016]
Figure7.PresentedbyAISandARPAinformationonCPA
of the cargo ship “SCL Basilea” (situation No 30, both
vesselswerealteringtheircoursesduringthemeasurement,
seastate3)[Wilczyński2016]
In all cases, information on the CPA and TCPA
presented by the AIS for vessels proceeding with
steadycourseandspeedwasatleastasstableasthe
values of these parameters indicated by the ARPA.
Figures8and9showexemplarygraphsofchangesof
CPAandTCPAasa
functionoftimeinthetestNo.
38.Theydemonstratethattheaccuracyofinformation
shownbyAISabouttheCPAandTCPAofobserved
vesselmaydependonthenumberofpositionreports
(AISmessages)receivedfromthatvessel.
Figure8.PresentedbyAISandARPAinformationonCPA
ofthecontainervessel“Varamo”(situationNo38,ownship
and “Varamo” were proceeding with steady courses and
speeds,seastate4)[Wesołowski2016]
Figure9.PresentedbyAISandARPAinformationonTCPA
ofthecontainervessel“Varamo”(situationNo38,ownship
and “Varamo” were proceeding with steady courses and
speeds,seastate4)[Wesołowski2016]
Often AIS presented measured parameters more
accuratelyandmuchmorestablethanARPA(Figures
10‐14).
Figure10.PresentedbyAISandARPAinformationonCPA
ofthe bulkcarrier“F.D.GennaroAurilia”(situationNo9,
ownshipand“F.D.GennaroAurilia”wereproceedingwith
steadycoursesandspeeds,seastate3)[Wesołowski2016]
Figure11. Presented by AIS and ARPA information on
TCPAofthebulkcarrier“F.D.GennaroAurilia”(situation
No 9, own ship and “F.D. Gennaro Aurilia” were
proceeding with steady courses and speeds, sea state 3)
[Wesołowski2016]
421
Figure12.PresentedbyAISandARPAinformationonCPA
of the container vessel “APL Vancouver” (situation No 1,
own ship and “APL Vancouver” were proceeding with
steadycoursesandspeeds,seastate4)[Wilczyński2016]
Figure13. Presented by AIS and ARPA information on
TCPA of the container vessel “APL Vancouver” (situation
No 1, own ship and “APL Vancouver” were proceeding
with steady courses and speeds, sea state 4) [Wilczyński
2016]
The higher accuracy and stability of CPA and
TCPAindicatedbytheAISintheabsenceoftheown
andoppositeships’manoeuvresisduetothegreater
accuracy and stability of information about the
oppositeship’scourseandspeed(Figures14‐17).
Figure14.PresentedbyAISandARPAinformationonthe
courseofthebulkcarrier“F.D.GennaroAurilia”(situation
No 9, own ship and “F.D. Gennaro Aurilia” were
proceeding with steady courses and speeds, sea state 3)
[Wesołowski2016]
Figure15.PresentedbyAISandARPAinformationonthe
speedofthebulkcarrier“F.D.GennaroAurilia”(situation
No 9, own ship and “F.D. Gennaro Aurilia” were
proceeding with steady courses and speeds, sea state 3)
[Wesołowski2016]
Figure16.PresentedbyAISandARPAinformationonthe
courseofthecontainervessel“APLVancouver” (situation
No 1, own ship and “APL Vancouver” were proceeding
with steady courses and speeds, sea state 4) [Wilczyński
2016]
Figure17.PresentedbyAISandARPAinformationonthe
speed of the container vessel “APL Vancouver” (situation
No 1, own ship and “APL Vancouver” were proceeding
with steady courses and speeds, sea state 4) [Wilczyński
2016]
SometimesAISpresentsvaluesofdescribedships
meeting parameters, mainly CPA, in an unstable
manner(Fig.18).Thereasonforthismaybeasmall
stability of the AIS information about the course
and/orspeedoftheoppositevessel(Fig.19,20).
422
Figure18.PresentedbyAISandARPAinformationonCPA
ofthecontainervessel“NYKAltair”(situationNo24,own
ship and “NYK Altair” were proceeding with steady
coursesandspeeds,seastate4)[Wilczyński2016]
Figure19.PresentedbyAISandARPAinformationonthe
course of the container vessel “NYK Altair” (situation No
24, own ship and “NYK Altair” were proceeding with
steadycoursesandspeeds,seastate4)[Wilczyński2016]
Figure20.PresentedbyAISandARPAinformationonthe
speedofthecontainervessel“NYKAltair”(situationNo24,
own ship and “NYK Altair” were proceeding with steady
coursesandspeeds,seastate4)[Wilczyński2016]
AIS advantages become apparent during the
observationofvesselsatanchoragewhenslewingof
shipatanchoraffectsthelowaccuracyofdataabout
CPA, TCPA, course and speed of that ship received
fromradartracking.Itmaybe seeninFigures21‐24
presenting the information on bulk carrier “China
Peace”stayingatanchor,shownbyAISandARPAon
shipapproachingtheanchoragefromthedistanceof
15M(27.8km).
Figure21.PresentedbyAISandARPAinformationonCPA
of the bulk carrier “China Peace” staying at anchor
(situation No 7, own ship was proceeding with steady
courseandspeed,seastate3)[Wilczyński2016]
Figure22. Presented by AIS and ARPA information on
TCPAof thebulk carrier “China Peace” staying at anchor
(situation No 7, own ship was proceeding with steady
courseandspeed,seastate3)[Wilczyński2016]
Figure23.PresentedbyAISandARPAinformationonthe
courseofthebulkcarrier“ChinaPeace”staying at anchor
(situation No 7, own ship was proceeding with steady
courseandspeed,seastate3)[Wilczyński2016]
423
Figure24.PresentedbyAISandARPAinformationonthe
speed of the bulk carrier “China Peace” staying at anchor
(situation No 7, own ship was proceeding with steady
courseandspeed,seastate3)[Wilczyński2016]
Figure25.PresentedbyAISandARPAinformationonCPA
ofthetanker“NCCDanah”(situationNo22,ownshipand
“NCC Danah” were proceeding with steady courses and
speeds,seastate7)[Wilczyński2016]
Another problem is the issue of the accuracy of
data presented by the AIS in adverse weather
conditions. As shown in Figures 25 and 26 the
accuracyandstabilityofdatapresented byAISmay
beonthesamelevelorevenworsethantheaccuracy
and stability of ARPA data.
The reason of that are
unstable instantaneous values of the course and/or
speedofobservedvesselindicatedbyAIS(Figures27
and 28). In Figures 25‐28 are presented data about
tanker“NCCDanah”sailingonthecrossingcoursein
heavystorm(seastate7degreesoftheDouglasscale).
Figure26. Presented by AIS and ARPA information on
TCPA of the tanker “NCC Danah” (situation No 22, own
ship and “NCC Danah” were proceeding with steady
coursesandspeeds,seastate7)[Wilczyński2016]
Figure27. Presented by AIS and ARPA information on
course of the tanker “NCC Danah” (situation No 22, own
ship and “NCC Danah” were proceeding with steady
coursesandspeeds,seastate7)[Wilczyński2016]
Figure28. Presented by AIS and ARPA information on
speed of the tanker “NCC Danah” (situation No 22, own
ship and “NCC Danah” were proceeding with steady
coursesandspeeds,seastate7)[Wilczyński2016]
Similarly,theproblemwithaccuracyandstability
ofinformationpresentedbyshipborneAISaboutthe
CPAandTCPAappearsinthecaseofahighswell.It
may be seen in Figures 29‐32 showing CPA, TCPA,
courseandspeedofcontainervessel“OOCLKorea”
sailingonthecrossingcoursein
theconditionofhigh
swell.
424
Figure29.PresentedbyAISandARPAinformationonCPA
ofthecontainervessel“OOCLKorea”(situationNo26,own
ship and “OOCL Korea” were proceeding with steady
coursesandspeeds,highswell)[Wilczyński2016]
Figure30. Presented by AIS and ARPA information on
TCPAofthecontainervessel“OOCLKorea”(situationNo
26, own ship and “OOCL Korea” were proceeding with
steadycoursesandspeeds,highswell)[Wilczyński2016]
Figure31.PresentedbyAISandARPAinformationonthe
courseofthecontainervessel“OOCL Korea”(situationNo
26, own ship and “OOCL Korea” were proceeding with
steadycoursesandspeeds,highswell)[Wilczyński2016]
Figure32.PresentedbyAISandARPAinformationonthe
speedofthecontainervessel“OOCLKorea”(situationNo
26, own ship and “OOCL Korea” were proceeding with
steadycoursesandspeeds,highswell)[Wilczyński2016]
4 CONCLUSIONS
The tests carried out have shown that information
presentedbyAISabouttheCPAandTCPAofother
vesselsisatleastasaccurateandstableovertimeas
the values of these parameters indicated by ARPA.
AIS shows data often more stable and precisely, for
exampleinthe
caseofshipsatanchor.The problem
requiring further research is the accuracy of the
information,mainlyabouttheCPA,presentedbythe
shipʹsAISinadverseweatherconditions.
REFERENCES
Resolution A.1106(29) “Revised guidelines for the
operational use of shipborne automatic identification
systems(AIS)”,IMO,London2015.
Resolution MSC.192(79) “Adoption of the revised
performance standards for radar equipment”, IMO,
London2004.
WawruchR.,Accuracyofinformationaboutshipsreceived
fromAISandradartrackingequipment,PolishJournal
ofEnvironmentalStudies,Vol.
17,No5A,2008,pp.94‐
98.
Wesołowski Jakub, Analiza porównawcza dokładności
danych o parametrach ruchu względnego i
rzeczywistego statku obcego prezentowanych przez
ARPA i AIS, engineering thesis, Gdynia Maritime
University,Gdynia2016.
Wilczyński Mateusz, Analiza porównawcza dokładności
śledzenia systemów AIS i ARPA,
engineering thesis,
GdyniaMaritimeUniversity,Gdynia2015.
www.google.pl/search?q=magdalena+oldendorff+ship&rlz
(24.07.2016).
www.vesselfinder.com/pl/vessels/PAMPERO‐IMO‐
9689548‐MMSI‐538006047(24.07.2016).
