Ship Targets.3-5; Echo Size.3-5 - Furuno 1751 Operator's Manual

Interpreting tha Display
3. APPUCATION
Ship targets
A bright, steady, clearly defined image appearing on the display is in all likelihood the target
pip of a Steel ship. There are several dues which can aid you in identification of a ship. Check
your navigational position to rule out the possibility that a target pip is actually a landmass.
Land and predpitation echoes are much more massive in appearance than the target pips of
ships — which are relatively small. The rate of movement can eliminate the possibility that
the pip is an aircraft.
A target pip may brighten and become dim due to changes in aspect and other factors. In
most cases however a pip will fade from the display only when the range becomes too great.
Echo size
As the radar beam rotates, the appearance of a pip on the display screen will begin as soon
as the leading edge of the radar beam strikes the target. The pip will continue to be seen on
the display screen until the trailing edge of the beam rotates beyond the target. Thus, a target
cannot appear less wide than the beamwidth. As the beam widens with distance from the
scanner, so also will the widths of targets vary on the display. Figure 3-3 illustrates the
relationship between beamwidth and the appearance of a target pip.
SHORT RANGE
TARGET
Figure 3-3 Beamwidth Versus Target Appearance
3-5