Chapter 3: Standard Radar Operations 3-23
MARPA
3.6 MARPA
Introduction to MARPA
The hsb
2
seriesdisplaysinclude a MARPA (Mini Automatic Radar Plotting
Aid)function for target tracking and risk analysis.This sectiongives an
introductiontothePathfinderPlusRadarMARPAsystemandshowsyouhow
to use the MARPA functions, you should also read Section 7.5.
MARPA improves the standard of collision avoidance by obtainingdetailed
information for several automaticallytracked targets. MARPAprovides
continuous, accurate and rapid situationevaluation.
You can acquire up to ten targets, which are then automaticallytracked by the
MARPA system. MARPAcalculatestargetbearing andrange, true speed and
course,CPA(ClosestPointofApproach),andTCPA(TimetoClosestPointof
Approach).
Each trackedtarget can be displayed with a vectordepicting approximate
target speed (vector length)and course (vector direction).The calculated
targetdatacanalsobeshownonthescreen.Eachtargetiscontinuallyassessed
and you are warned if one becomes dangerous or is lost.
EffectiveMARPA operationis dependent on accurate own ship’s heading,
plus SOG andCOG. The better the quality of the heading data, the better
MARPA willperform. (MARPA functions without SOG and COG data but
onlyrelative vector,CPA and TCPA are shown; targetcourse and speed
cannot be calculated).For more information on heading sensors,and how to
connectthemto your display,refertoHeadingand PositionData on page 1-9
and Appendix E.
SAFETY NOTICES
MARPA can improve collision avoidancewhen used wisely. It is the
user’s responsibilityto exercisecommon prudence and navigational
judgements.
Thereareconditionswhereacquiringatargetmaybecomedifficult.These
same conditions may be a factor in successfully tracking a target. Some of
the conditions are:
• The targetecho is weak.
• The targetis very closeto land, buoys or other largetargets.
• The targetor your own ship is making rapid manoeuvres.
• Choppy sea state conditions exist and the target is buriedin excessive
sea clutteror in deep swells.
81186_3.book Page 23 Thursday, August 22, 2002 8:23 AM
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