Raymarine Combined Pathfinder Radar Using Marpa, Target Vector and History, Repeater Displays

Chapter 3: Standard Radar Operations 3-25

Target Vector and History

The MARPA targets can be displayed with a vector line showing where they will be at a certain time in the future, (assuming present course and speed). You can select a relative or true vector and the vector length. The vector type (RV or TV) and length are shown in the status bar.

You can also select to view the target’s history, this appears as a series of dots that are dropped by the target as it makes way. The interval between them is selectable.

A relative vector indicates the target’s motion related to your own ship’s motion. The target’s relative course and speed are calculated to produce a vector that is displayed on the target only. This mode is used for collision avoidance and threat assessment.

A true vector indicates the target’s motion over ground. In this mode true vectors for the target and your own ship are displayed. MARPA measures the direction in which the target and own ship are actually moving over the ground. The result is the vessel’s true course, the rate of motion is the vessel’s true speed. Consider this motion as if you were in a helicopter looking down watching the targets move across the water. This mode can aid navigation.

Section 7.5 describes how to set the target vector and history parameters.

Repeater Displays

On an integrated hsb2 display system the repeater display (with the appropriate software version) can access the MARPA functions, and targets are shown on the repeater display. MARPA data is also sent on NMEA allowing any other equipment, with the necessary functionality, to show the tracked targets’ data.

Radar Range Scales

MARPA target acquisition is only available at radar range scales of up to 12nm, although tracking continues at all ranges.

Note: If you change to a lower range scale, targets may be beyond the range of the scanner and will be lost. In such cases an alarm pop-up indicates the target is off-screen.

Using MARPA

The MARPA functions are accessed through the MARPA default soft key, and some options are available with the context sensitive cursor, or through the MARPA database list. Where there are two ways of performing a certain function this section describes both ways. Information on how to set up the MARPA system is in Section 7.5.

Using MARPA