Chapter 3: Standard Radar Operations 3-25
Using MARPA
Target Vector and History
The MARPA targets can be displayed with a vector line showing wherethey
will be at a certain time in the future, (assuming presentcourse and speed).
You can selecta relativeor 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 targetas it makes way. The intervalbetween them is
selectable.
A relative vector indicates the target’s motion relatedto yourown ship’s
motion.The target’s relative course and speed are calculatedto produce a
vectorthat is displayed on the targetonly. This mode is used for collision
avoidance and threat assessment.
A true vectorindicates thetarget’s motion over ground. In this mode true
vectorsfor the target and your own ship are displayed.MARPA measuresthe
direction inwhich the targetand own ship are actuallymoving over the
ground.The result is the vessel’s true course,the rateof motionisthe vessel’s
true speed. Considerthis 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 describeshow to set the targetvector and history parameters.
Repeater Displays
Onanintegratedhsb
2
displaysystemtherepeaterdisplay(withtheappropriate
softwareversion)can access the MARPA functions,and targetsare shown on
the repeater display.MARPA datais also sent on NMEA allowingany other
equipment, with the necessaryfunctionality, to show the trackedtargets’data.
Radar Range Scales
MARPA targetacquisitionis onlyavailableat radar range scales of up to
12nm, although trackingcontinuesat 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 defaultsoft key, and
some options are available withthe context sensitive cursor, or through the
MARPA database list. Where there are two ways of performing a certain
functionthis section describes bothways. Information on how to set up the
MARPA system is in Section 7.5.
81186_3.book Page 25 Thursday, August 22, 2002 8:23 AM
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