Garmin GPSMAP 8500, Owner'S Manual

Page: 37 / 66

Especially in inclement weather, longer-range radar signals
can increase the clutter on the Radar screen and make it
more difficult to view information about shorter-range targets.
In rain, shorter-range radar signals can enable you to view
information about nearby objects more effectively, if the rain
clutter setting is configured optimally.
• Select the shortest effective range, given your reason for
using radar and the present environmental conditions.
MotionScope
™
Doppler Radar Technology
The GMR Fantom radar uses the Doppler effect to detect and
highlight moving targets to help you avoid potential collisions,
find flocks of birds, and track weather formations. The Doppler
effect is the frequency shift in the radar echo due to the relative
motion of the target. This allows for instant detection of any
targets moving toward or away from the radar.
The MotionScope feature highlights the moving targets on the
radar display so you can navigate around other boats or severe
weather, or toward fishing spots where birds are feeding at the
surface.
The moving targets are color-coded so you can tell at a glance
which targets are heading your way and which are heading
away from you. On most color schemes, green indicates the
target is moving away from you and red indicates the target is
moving toward you.
Enabling a Guard Zone
You can enable a guard zone to alert you when anything comes
within a specified area around your boat.
NOTE: This feature is not available in dual radar modes.
From a radar screen, select Menu > Radar Options >
Enable Guard Zone .
Defining a Circular Guard Zone
Before you can define the boundaries of the guard zone, you
must enable a guard zone ( Enabling a Guard Zone , page 29 ).
You can define a circular guard zone that completely surrounds
your boat.
1
From a radar screen, select Menu > Radar Options >
Adjust Guard Zone > Adjust Guard Zone > Circle .
2
Select the location of the outer guard zone circle.
3 Select the location of the inner guard zone circle to define the
width of the guard zone.
Defining a Partial Guard Zone
Before you can define the boundaries of the guard zone, you
must enable a guard zone ( Enabling a Guard Zone , page 29 ).
You can define the boundaries of a guard zone that does not
completely surround your boat.
1 From a radar screen, select Menu > Radar Options >
Adjust Guard Zone > Adjust Guard Zone > Corner 1 .
2
Touch and drag the location of the outer guard-zone corner
À
.
3 Select Corner 2 .
4 Touch the location of the inner guard-zone corner
Á
to define
the width of the guard zone.
5
Select Done .
Disabling a Guard Zone
You can disable a guard zone.
From a radar screen, select Menu > Radar Options >
Adjust Guard Zone > Disable Guard Zone .
The guard zone configuration is saved, so you can enable it
again when needed.
MARPA
Mini-automatic radar plotting aid (MARPA) enables you to
identify and track targets and is primarily used for collision
avoidance. To use MARPA, you assign a MARPA tag to a
target. The radar system automatically tracks the tagged object
and provides you with information about the object, including the
range, bearing, speed, GPS heading, nearest approach, and
time to nearest approach. MARPA indicates the status of each
tagged object (acquiring, lost, tracking, or dangerous), and the
chartplotter can sound a collision alarm if the object enters your
safe zone.
MARPA Targeting Symbols
Acquiring a target. Concentric, dashed green rings radiate from
the target while the radar is locking onto it.
Target has been acquired. A solid green ring indicates the
location of a target that the radar has locked onto. A dashed
green line attached to the circle indicates the projected course
over ground or the GPS heading of the target.
Dangerous target is in range. A red ring flashes from the target
while an alarm sounds and a message banner appears. After
the alarm has been acknowledged, a solid red dot with a dashed
red line attached to it indicates the location and the projected
course over ground or the GPS heading of the target. If the safe-
zone collision alarm has been set to Off, the target flashes, but
the audible alarm does not sound and the alarm banner does
not appear.
Target has been lost. A solid green ring with an X through it
indicates that the radar could not lock onto the target.
Closest point of approach and time to closest point of approach
to a dangerous target.
Assigning a MARPA Tag to an Object
Before you can use MARPA, you must have a heading sensor
connected and an active GPS signal. The heading sensor must
provide the NMEA 2000 parameter group number (PGN)
127250 or the NMEA 0183 HDM or HDG output sentence.
1
From a radar screen, select an object or location.
2
Select Acquire Target > MARPA Target .
Removing a MARPA Tag from a Targeted Object
1
From the Radar screen, select a MARPA target.
2
Select MARPA Target > Remove .
Viewing Information about a MARPA-tagged Object
You can view the range, bearing, speed, and other information
about a MARPA-tagged object.
Radar 29