Product specifications

Chapter 3: Standard Radar Operations 3-23

MARPA

3.6 MARPA

Introduction to MARPA

The hsb

series displays include a MARPA (Mini Automatic Radar Plotting

Aid) function for target tracking and risk analysis. This section gives an

introduction tothe PathfinderPlusRadarMARPAsystemandshowsyouhow

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 acquire up to ten targets, which are then automatically tracked by the

MARPA system. MARPA calculates targetbearing and range, true speed and

course,CPA(ClosestPointofApproach),andTCPA(TimetoClosest Pointof

Approach).

Each tracked target can be displayed with a vector depicting approximate

target speed (vector length) and course (vector direction). The calculated

targetdatacanalso beshown onthescreen.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 to your display, referto Heading and PositionDataon page 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 conditionswhere acquiringa targetmay 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.