Chapter 3-4
CR44/54 Radar menu
moving on a map or chart. In True motion mode, the surrounding
landmass echoes remain stationary on the screen and if your ship
is moving at a constant course and speed, you will see your posi-
tion move across the screen towards the edge of the display. Any
other targets which are underway will also be moving on the display
screen at their True course and True speed. All motion seen on the
True motion display is “TRUE” (meaning motion over the ground).
3.1.4 Navigational echoes
Echoes displayed on the radar screen may be large or small, bright
or faint, depending on the size and shape of the object and its angle
relative to your radar antenna. The radar indication is not always the
same as an observer’s visual indication; a nearby small object may
appear to be the same size as a distant large object on the radar. With
experience, however, different targets can be identified by the rela-
tive size, brightness, and position of their radar echo returns.
Buoys and small boats are one example of targets that are sometimes
difficult to distinguish from each other. Their movement in the
waves do not present a consistent reflecting surface. Consequently,
their echoes have a tendency to fade and brighten or sometimes
to disappear momentarily. Although buoys and small boats often
resemble each other, usually the motion of one target identifies the
boat from the buoy.
High coastlines and mountainous coastal regions are often observed
at the longest ranges of the radar. However, the first sight of landfill
on the radar’s longest ranges may be a mountain several miles inland
from the coastline and not the actual coastline. The coastline may
not appear on the radar until the vessel has approached land nearer
the line of sight distance.
3.1.5 Racon (Radar Beacon)
A racon is a radar transponder which emits a characteristic signal
when triggered by a ship’s radar. The signal may be emitted on the
same frequency as that of the triggering radar, in which case it is
superimposed on the ship’s radar screen automatically.
The racon signal appears on the screen as a radial line originating
at a point just beyond the position of the radar beacon or as a Morse
code signal displayed radially from just beyond the beacon.
