Raymarine C140w - Page 125

8.PresstheOKbutton.
Enablinganddisablingradarwarningalarms
1.PresstheMENUbutton.
2.Usingthetrackpad,highlighttheAlarmSetupmenuitemand
pressthetrackpadrighttoselectit.
3.Usingthetrackpad,highlighttheRadarAlarmsSetupmenuitem
andpressthetrackpadrighttoselectit.
MARPAoverview
MARPAisusedfortargettrackingandriskanalysisintheradar
application.
YoucanusetheMiniAutomaticRadarPlottingAid(MARPA)
functionsfortargettrackingandriskanalysis.MARPAimproves
collisionavoidancebyobtainingdetailedinformationfor
automaticallytrackedtargets,andprovidescontinuous,accurate,
andrapidsituationevaluation.Thenumberoftargetsthatyoucan
trackatanyonetimeisdependentonthemodelofradarscanner
thatyouareusing.
MARPAautomaticallytracksacquiredtargets,calculatestarget
bearingandrange,speedandcourse,ClosestPointofApproach
(CPA),andTimetoClosestPointofApproach(TCPA).
EachtargettrackedcanbedisplayedwithaCPAgraphicwhich
showsthetargetvessel,courseandspeed(asavector)and
indicatestheCPA.Thecalculatedtargetdatacanalsobeshown
onyourscreen.Eachtargetiscontinuallyassessedandanaudible
alarmissoundedifatargetbecomesdangerous,orislost.
EffectiveMARPAoperationisdependantonaccurateown-ship’s
headingandspeed.SpeedOverGround(SOG)andCourseOver
Ground(COG)informationarerequiredtoshowtruetargetcourse
andspeed.Thebetterthequalityoftheheadingandspeeddata,
thebetterMARPAwillperform.MARPAwillfunctionwithoutSOG
andCOGinrelativemode.ForthebestheadingdataaRaymarine
SMARTheadingsensororagyro-stabilizedautopilotisrequired.
Safetynotices
MARPAcanimprovecollisionavoidancewhenusedwisely.Itisthe
User’sresponsibilitytoexercisecommonprudenceandnavigational
judgements.
Thereareconditionswhereacquiringatargetmaybecomedifcult.
Thesesameconditionsmaybeafactorinsuccessfullytrackinga
target.Someoftheconditionsare:
•Thetargetechoisweak.Thetargetisveryclosetoland,buoys
orotherlargetargets.
•Thetargetoryourownshipismakingrapidmanoeuvres.
•Choppyseastateconditionsexistandthetargetisburiedin
excessiveseaclutterorindeepswells.
•Choppyseastateconditionsexistyieldingpoorstability;own
boat’sheadingdataisveryunstable.
•Inadequateheadingdata.
Symptomsofsuchconditionsarethatacquisitionisdifcultandthe
MARPAvectorsareunstable;thesymbolwandersawayfromthe
target,locksontoanothertargetorchangestoalostsymboltarget.
Ifanyoftheseconditionsarepresent,acquisitionandtrackingmay
needtobere-initiatedor,insomecasesbeimpossibletomaintain.
Improvingthequalityoftheheadingdatawillreducetheeffectof
theotherconditions.
HowaMARPAriskisassessed
Eachtargetismonitoredtoseeifitwillbewithinacertaindistance
fromyourboatwithinacertaintime.Ifso,thetargetisdesignated
asdangerousandanaudiblewarningissoundedalongwithan
on-screenwarningbeingshown.Thetargetsymbolchangesto
Usingradar
125