Raymarine C140w - Manual (Page 105)

With experience, the approximate size of different objects can be
determined by the relative size and brightness of the echoes.
You should bear in mind that the size of each on-screen target is
affected by:
• The physical size of the reflecting object.
• The material from which the object is made. Metallic surfaces
reflect signals better than non-metallic.
• Vertical objects such as cliffs reflect signals better than sloping
objects such as sandbanks.
• High coastlines and mountainous coastal regions can be observed
at longer radar ranges. Therefore, the first sight of land may be a
mountain several miles inland from the coastline. Although the
coastline may be much nearer, it may not appear on the radar
until the vessel is closer to shore.
• Some targets, such as buoys and small boats, can be difficult
to discern, because they do not present a consistent reflecting
surface as they bob and toss about in the waves. Consequently,
these echoes tend to fade and brighten and at times, to disappear
momentarily.
• Buoys and small boats often resemble each other, but boats can
often be distinguished by their motion.
Note: You will need heading and position data for full functionality
of your radar. A fast heading sensor is also needed for operation
of MARPA and can maximize the performance of radar/chart
overlay.
9.5 Dual range radar operation (digital
scanners only)
Dual Range radar operation enables you to view two ranges at the
same time, in separate windows.
Using your multifunction display and a digital radar scanner, you
can view either a short or a long range image in separate radar
windows. To allow this, Dual Range must be enabled in the Radar
Setup Menu (MENU > Radar Setup > Scanner Setup).
The default setting is Long, which provides a standard scanner
range. The Short setting provides a maximum range of three
nautical miles. The Long range value cannot be less than the
current Short range value. For example, if Short range is set to
3nm, Long range cannot be less than 3nm.
Limitations
• Dual Range operation is not available if MARPA is ON.
• You cannot acquire MARPA targets if Dual Range is enabled.
• Chart-sync and chart overlay are temporarily disabled when Dual
Range is enabled.
Using Dual Range with SuperHD radar
When using the Short Dual Range option, a SuperHD radar
operates in HD mode only. When using the Long Dual Range
option, a SuperHD radar operates in SuperHD mode for all ranges:
Dual Range Range covered Operation
LONG 1/8nm to 72nm SuperHD
SHORT 1/8nm to 1½nm HD
Using radar 105