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HSB Series CRT Display
MARPA
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 MARPA Set Up
describes how to set the target vector and history
parameters.
Repeater Displays
On an integrated HSB 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.
10" CRT Radar Range Scales
MARPA target acquisition is only available at radar range scales of up to 12nm,
although tracking continues at all ranges.
Providing Heading Data for MARPA
The performance of MARPA on the 10" CRT radar display is dependent on the
quality of your heading sensor. In particular, MARPA requires heading data to
be frequently updated (i.e a minimum data output rate of 8 Hz). Heading data
must therefore be provided on NMEA.
The Raytheon ST80 Active (fluxgate) Compass connected on NMEA should
provide good results in reasonable sea states. However, in poor conditions, a
fluxgate compass with rate gyro, or a gyro compass will improve the
performance of MARPA. Contact Raytheon Customer Services or your
authorised Raytheon dealer for additional information.
For specific configuration and calibration details with the ST80 active compass
refer to Appendix F. If you are using a suitable third party heading sensor, refer
to its documentation for installation and calibration details; connect such a
compass in a similar manner to the ST80 active compass, giving due
consideration to the power requirements.
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