Raymarine Raychart Chartplotter RC530 PLUS, RL80CRC PLUS manual Introduction to Marpa

Chapter 3: Standard Radar Operations 3-23

3.6MARPA

Introduction to MARPA

The hsb2 series displays include a MARPA (Mini Automatic Radar Plotting Aid) function for target tracking and risk analysis. This section gives an introduction to the Pathfinder Plus Radar MARPA system and shows you how 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 target bearing and range, true speed and course, CPA (Closest Point of Approach), and TCPA (Time to Closest Point of Approach).

Each tracked target can be displayed with a vector depicting approximate target speed (vector length) and course (vector direction). The calculated target data can also be shown on the screen. Each target is continually assessed 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 connect them to your display, refer to Heading and Position Data on page 1-9and Appendix E.

SAFTEY NOTICES

MARPA can improve collision avoidance when used wisely. It is the user’s responsibility to exercise common prudence and navigational judgements.

There are conditions where acquiring a target may 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.

MARPA