Furuno FAR-3230SW-BB Manual De Usuario
2. RADAR, CHART RADAR OPERATION
2-66
Bearing resolution
Bearing resolution is the ability of the radar to display as separate pips the echoes re-
ceived from two targets which are at the same range and close together. It is propor-
tional to the antenna length and reciprocally proportional to the wavelength. The
length of the antenna radiator should be chosen for a bearing resolution better than
2.5° (IMO Resolution). This condition is normally satisfied with a radiator of 1.2 m (4
ft) or longer in the X-band. The S-band radar requires a radiator of about 12 feet (3.6
m) or longer.
Bearing resolution is the ability of the radar to display as separate pips the echoes re-
ceived from two targets which are at the same range and close together. It is propor-
tional to the antenna length and reciprocally proportional to the wavelength. The
length of the antenna radiator should be chosen for a bearing resolution better than
2.5° (IMO Resolution). This condition is normally satisfied with a radiator of 1.2 m (4
ft) or longer in the X-band. The S-band radar requires a radiator of about 12 feet (3.6
m) or longer.
Range resolution
Range resolution is the ability to display as separate pips the echoes received from
two targets which are on the same bearing and close to each other. This is determined
by pulse length only. Practically, a 0.08 microsecond pulse offers the discrimination
better than 40 m as do so with all FURUNO radars. Test targets for determining the
range and bearing resolution are radar reflectors having an echoing area of 10 m
Range resolution is the ability to display as separate pips the echoes received from
two targets which are on the same bearing and close to each other. This is determined
by pulse length only. Practically, a 0.08 microsecond pulse offers the discrimination
better than 40 m as do so with all FURUNO radars. Test targets for determining the
range and bearing resolution are radar reflectors having an echoing area of 10 m
2
(X-
band) or 1 m
2
(S-band).
Bearing accuracy
One of the most important features of the radar is how accurately the bearing of a tar-
get can be measured. The accuracy of bearing measurement basically depends on
the narrowness of the radar beam. However, the bearing is usually taken relative to
the ship's heading, and thus, proper adjustment of the heading line at installation is an
important factor in ensuring bearing accuracy. To minimize error when measuring the
bearing of a target, put the target echo at the extreme position on the screen by se-
lecting a suitable range.
One of the most important features of the radar is how accurately the bearing of a tar-
get can be measured. The accuracy of bearing measurement basically depends on
the narrowness of the radar beam. However, the bearing is usually taken relative to
the ship's heading, and thus, proper adjustment of the heading line at installation is an
important factor in ensuring bearing accuracy. To minimize error when measuring the
bearing of a target, put the target echo at the extreme position on the screen by se-
lecting a suitable range.
2.42.2
False echoes
Occasionally echo signals appear on the screen at positions where there is no target
or disappear even if there are targets. They are, however, recognized if you under-
stand the reason why they are displayed. Typical false echoes are shown below.
or disappear even if there are targets. They are, however, recognized if you under-
stand the reason why they are displayed. Typical false echoes are shown below.
Multiple echoes
Multiple echoes occur when a transmitted pulse returns from a solid object like a large
ship, bridge, or breakwater. A second, a third or more echoes may be observed on the
display at double, triple or other multiples of the actual range of the target as shown
below. Multiple reflection echoes can be reduced and often removed by decreasing
the gain (sensitivity) or properly adjusting the sea clutter.
Multiple echoes occur when a transmitted pulse returns from a solid object like a large
ship, bridge, or breakwater. A second, a third or more echoes may be observed on the
display at double, triple or other multiples of the actual range of the target as shown
below. Multiple reflection echoes can be reduced and often removed by decreasing
the gain (sensitivity) or properly adjusting the sea clutter.
Own ship
Target
True
echo
echo
Multiple echo