Furuno 1823C manual Radar resolution, Bearing resolution, Range resolution, Bearing accuracy

2. RADAR OPERATION

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 trackball 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 trackball is rolled 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.

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