Furuno GD-1700, Operator'S Manual

Page: 139 / 249

3. RADAR OPERATION
3-45
Radar resolution
There are two important factors in radar resolution (discrimination): bearing
resolution and range resolution.
Bearing resolution
Bearing resolution is the ability of the radar to display the echoes received from
two targets, which are at the same range and close together, as separate targets.
Bearing resolution is directly proportional to the antenna length, and inversely
proportional to the radar's wavelength.
Range resolution
Range resolution is the ability to display the echoes received from two targets,
which are on the same bearing and close to each other, as separate targets.
Bearing accuracy
One of the most important features of the radar is how accurately the bearing of
a target 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
marker at installation is an important factor in ensuring bearing accuracy. To
minimize error when measuring the bearing of a target, select a range which will
put the target as far out to the edge of the radar screen as possible.
Range measurement
Measurement of the range to a target is also a very important function of the
radar. There are three means of measuring range: the fixed range rings, the
cursor and the variable range marker (VRM). The fixed range rings appear on
the screen with a predetermined interval and provide a rough estimate of the
range to a target. The cursor pad is operated to place the cursor on the leading
edge of the target. Range and bearing to the target is shown at the bottom
right-hand corner of the display. The variable range marker’s diameter is
increased or decreased so that the marker touches the inner edge of the target,
allowing the operator to obtain more accurate range measurements.