User's Manual

MDC-5200/5500 Series Chapter 8 Principal of radar system
0093155002-03 8-3
Radar shadow
Since radar radio wave is line of sight in nature your stack mast close to the antenna or, a large ship or
mountain may create blind spots for which the radar cannot penetrate. In such cases, they may
completely or partially hide targets and cast a long shadow.
Since the shadow of your stack or mast is known at the time of installation, proper selection of the
antenna location is necessary to reduce the shadow effect. Since targets in this shadow area is less
likely to be seen than in open sea, extra attention should be paid in shadowed areas.
False image
An image that does not actually exist (false image) at sea may appear on the display.
The phenomena that causes false echoes are categorized and be described as follows:
●
Virtual image
The image of a large physical object in proximity may appear in two different orientations. One is a real
image and the other is a false image caused by wave re-reflected by the stack or the mast, etc. On the
display, one image appears at the correct distance and bearing, and another one appears in the
direction of a stack, a mast, etc. These images may also be generated by re-reflection from bridges and
quays too.
Passage of direct
reflection
Passage of
secondary
reflection
Direction of false image
Real image
False image
False image caused by virtual image
Mast, etc