Raymarine a67 Wi-Fi Installation And Operation Instructions Manual page 178

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 vessel is making rapid manoeuvres.
• Choppy sea state conditions exist and the target is buried in
excessive sea clutter or in deep swells.
• Choppy sea state conditions exist yielding poor stability; own
vessel's heading data is very unstable.
• Inadequate heading data.
Symptoms of such conditions include:
• target acquisition is difficult and the MARPA vectors are
unstable;
• the symbol wanders away from the target, locks-on to another
target, or changes to a lost symbol target.
In these circumstances, target acquisition and tracking may
need to be re-initiated and in some cases might be impossible
to maintain. Better quality heading data might improve
performance in these circumstances.
How a MARPA risk is assessed
Each target is monitored to ascertain whether it will be within a
certain distance from your vessel within a certain time. If so, the
target is designated as dangerous, and an audible warning is
sounded and a warning displayed. The target symbol changes
to the dangerous target symbol and flashes to indicate that it is
a dangerous target. Acknowledging the alarm will remove the
warning.
If a target is lost, either because the MARPA software has
lost contact with it, or because it has moved out of range, an
audible alarm is sounded and an on-screen warning appears.
The on-screen symbol will change to the target lost symbol.
Acknowledging the warning will silence the alarm and remove
the on-screen warning and the target lost symbol.
Effective range for MARPA targets
MARPA target acquisition is only available at radar range scales
of up to 12 nm, although tracking continues at all ranges.
If you change to a smaller range scale, targets may be beyond
the range of your radar scanner and will be lost. In such cases,
an on-screen warning indicates that the target is off-screen.
MARPA context menu
The MARPA function includes a context menu which provides
positional data and menu items.
The context menu provides the following target information:
• CPA
• TCPA
• COG
• SOG
The context menu also provide the following menu items:
• Cancel target
• CPA Graphic
• MARPA Data
• Slew thermal camera (Only available when thermal camera
is connected and operating.)
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Accessing the context menu
You can access the context menu by following the steps below.
1. New e Series or New c Series:
i. Selecting a location, object or target on-screen and
pressing the Ok button.
2. Touchscreen multifunction displays:
i. Selecting an object or target on-screen.
ii. Selecting and holding on a location on-screen.
Configuring MARPA options
From the radar application:
1. Select Menu.
2. Select Track Targets.
3. Select MARPA Options.
Note: If AIS data is available the menu will be MARPA & AIS
Options.
4. Select Vector Length.
5. Select an appropriate time period.
The distance that your vessel travels in the time period you
specify here determines the length of the vector lines.
6. Select MARPA Target History.
7. Select an appropriate time period.
The target's previous position will be plotted on the radar
display as a target icon with lighter shading than the actual
target.
Note: MARPA and AIS functions share Safe Zone and
Vector Length settings.
Configuring safe zone set up for MARPA
From the Radar application:
1. Select Menu.
2. Select Track Targets.
3. Select Safe Zone Set-up.
4. Select Safe Zone Radius.
i. Select a distance for the Safe Zone.
This is the distance from your vessel that the safe zone
will be set up.
5. Select Time to Safe Zone.
i. Select a time period.
A target is considered dangerous if it will enter your safe
zone within this time period.
6. Select Safe Zone Ring.
Selecting safe zone ring will switch between showing and
hiding the safe zone ring in the radar application.
Using MARPA
Acquiring a MARPA target to track
From the radar application:
1. Select the target to be acquired.
The MARPA context menu is displayed.
2. Select Acquire Target.
The "target being acquired" symbol is displayed. If the target is
present for several scans, the radar locks-on to the target, and
the symbol changes to "safe target" status.
Cancelling a MARPA target using the MARPA context menu
From the radar application:
1. Select the relevant target.
The MARPA context menu is displayed.
2. Select Cancel Target or Cancel All Targets.
Cancelling a MARPA target using the menu
1. Select Menu.
2. Select Track Targets.
3. Select View MARPA Lists.
Note: If AIS data is available the menu will be View MARPA
& AIS Lists.
New a Series / New c Series / New e Series