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Appendix I: Glossary
Anti-Rain Clutter (FTC): used to reduce or eliminate massive num-
ber of small echoes that clutter the display during rain or snow storms.
Anti-Sea Clutter (STC): lowers receiver sensitivity at shorter ranges
to reduce or eliminate sea clutter echoes, which are most prevalent
around the vessel.
ARPA: automatic radar plotting aid; MARPA: mini automatic radar
plotting aid. ARPA allow you to monitor multiple targets, providing
updates on the target's course and speed, then plotting them in vector
format on the display. MARPA does the same thing, but can only moni-
tor a small number of targets. These navigation aids usually are avail-
able in only North-Up stabilized mode.
Beam: focused rays of microwave energy
Beam width: measured in degrees, the width of a beam, both horizon-
tally and vertically.
Clutter: undesirable echoes created by rain, snow, waves and other
intermittent causes.
Course Up: a mode in which the direction travel is represented at the
top of the radar display.
EBL (Electronic Bearing Line): A radial line that can be rotated
360º, the electronic bearing line is used to monitor the bearing of a ra-
dar target in relation to your location.
Echo: reflected radio frequency pulse picked up by radar. It is also an-
other name for a target image detected on the radar display.
Echo trail: a history (trail) of the echoes for a particular radar target.
Gain: used to adjust the sensitivity of the receiver to increase or de-
crease the intensity of images on the display.
Ghost Echo: an undesirable image created when returns are reflected
off other structures.
Guard Zone: an area selected by the radar user, that when activated,
will sound an alarm if any echo passes into the zone.
Heading Flash: the green line on the radar display that shows the
direction you are heading.
