
Chapter 5: Using the Radar 5-7
5.4 What does the radar picture show me?
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 radar/chart overlay
functions.
With your radar scanner connected and the radar in transmit mode, the radar picture,
provides a map-like representation of the area in which the radar is operating e.g.
Typically, your boat’s position is at the centre of the display, and its dead ahead bearing
is indicated by a vertical heading line, known as the Ship’s Heading Marker (SHM).
On-screen targets may be large, small, bright or faint, dependent on the size of the
object, its orientation and surface. Strongest target returns are displayed in yellow
with weaker returns in two shades of blue. Be aware that the size of a target on screen
is dependent on many factors and may not necessarily be proportional to its physical
size. Nearby objects may appear to be the same size as a distant larger objects.
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.
3nm
Head-Up Relative Motion Rings ½nm
VRM/EBL... GAIN...
PRESENTATION...
TARGET
TRACKING...
TARGETS
DISPLAY...
D6803-2
Orientation
Data bar
Surface
vessel
Waypoint
Ship's
heading
marker
Icon
confirming
radar
connection
Range
ring
Landmass
Boat's
position
Range
Motion mode Range ring spacing
81244_1.book Page 7 Wednesday, December 1, 2004 11:41 AM
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