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Chapter 3: Standard Radar Operations 3-23
MARPA
3.6 MARPA
Introduction to MARPA
The hsb
2
series displays include a MARPA (Mini Automatic Radar Plotting
Aid) function for target tracking and risk analysis. This section gives an
introductionto thePathfinderPlusRadar MARPA systemand showsyouhow
to use the MARPA functions, you should also read Section 7.5.
MARPA improves the standard of collision avoidance by obtaining detailed
information for several automatically tracked targets. MARPA provides
continuous, accurate and rapid situation evaluation.
You can acquireup to ten targets, which are then automatically tracked by the
MARPA system. MARPA calculates target bearing and range, true speed and
course,CPA(ClosestPoint ofApproach),andTCPA(TimetoClosestPointof
Approach).
Each tracked target can be displayed with a vector depicting approximate
target speed (vector length) and course (vector direction). The calculated
targetdatacan alsobe shown onthe screen.Eachtargetiscontinuallyassessed
and you are warned if one becomes dangerous or is lost.
Effective MARPA operation is dependent on accurate own ship’s heading,
plus SOG and COG. The better the quality of the heading data, the better
MARPA will perform. (MARPA functions without SOG and COG data but
only relative vector, CPA and TCPA are shown; target course and speed
cannot be calculated). For more information on heading sensors, and how to
connectthem toyour display, refer to Headingand Position Data onpage 1-9
and Appendix E.
SAFETY NOTICES
MARPA can improve collision avoidance when used wisely. It is the
user’s responsibility to exercise common prudence and navigational
judgements.
Thereare conditions where acquiring atargetmay become difficult.These
same conditions may be a factor in successfully tracking a target. Some of
the conditions are:
• The target echo is weak.
• The target is very close to land, buoys or other large targets.
• The target or your own ship is making rapid manoeuvres.
• Choppy sea state conditions exist and the target is buried in excessive
sea clutter or in deep swells.
81186_3.book Page 23 Thursday, August 22, 2002 8:23 AM