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/50 MKII Radar operation
Chapter 7
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when maneuvering around nearby vessels, or buoys.
The True motion display mode can be compared to your vessel 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 position 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).
7.1.4 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 relative
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.
7.1.5 Sea return
Not all radar echoes are produced by hard navigation items such as
boats, buoys and land. Some radar echoes may be received from
irregularities on the surface of the water, particularly at close range by
