Jeppesen Marine Workboat Navigator 1.3 - Manual (Page 123)

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12
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Radar
12 - Radar Management
Reducing Sea Clutter (SEA)
Use the Sea Up and Sea Down controls or slider bar to reduce the effect of random
echo returns from waves or rough water near the boat. Sea Clutter is sometimes
referred to as STC (Slow Time Constant) or just SEA.
Reducing the on-screen clutter caused by the echoes of waves is accomplished by
increasing the SEA value.
Sea Clutter shows on your radar screen as a thick cluster of radar returns.
Increasing the Slow Time Constant can help filter out the echoes between rough
seas and real targets
Sea function adjusts the image to dynamically compensate for changing sea state
due to wind or swells. Jeppesen Workboat Navigator radar interface evaluates the
type of echoes returned and applies Sea Clutter control from the center of the radar
image outward.
One benefit of the Sea setting is that if the sea state increases due to apparent
wind changes, more Sea Clutter control is automatically applied on the leeward side
of the image to counteract wave chop on that side of the boat.
As with the Gain setting, Sea Clutter applies to all ranges. Due to the nature of Sea
Clutter filtering, Jeppesen Workboat Navigator applies sea clutter based on the STC
Curve profile, and generally has greater application closer to the boat.
To adjust the Sea Clutter Preset:
Set the radar range to 12nm.
Direct focus to the Radar window pane and select Context Menu | Tuning.
Manually adjust the Gain until you get secondary echoes throughout the image.
Adjust the Sea value up until most of the weak echoes for an 8 nm radius are
eliminated.
Adjust the radar range to 1.5 nm and verify that strong echoes from nearby
boats or land are not eliminated. If land or boat echoes are small or have been
eliminated, repeat the steps above to decrease Sea Clutter preset.
Figure 12.3 - Sea Clutter
Rain
The vertical beam width of the radar antenna allows you to see targets on the
surface even when a boat is rolling. This feature, however, can have the side effect
of confusing rain, snow or other conditions with real targets. Increasing the Rain
value helps to discriminate between weather and solid returns.
Use the Rain Up and Rain Down controls or slider bar to reduce the effect of
weather or other meteorological phenomenon on your radar image. Be careful not
to increase the rain value too much as it can filter out real targets with the weather.
Rain Clutter control is still effective when the Gain is lowered.
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