Radar range

Minimum range

Radar performance on larger ships may suffer from shadowing where the minimum radar detection range is degraded by a combination of antenna height, ship structures and cargo. The minimum range is defined by the shortest distance at which, using a scale of 1.5 NM or 0.7 NM, a target having an echoing area of 10 m2 is still shown separate from the point representing the antenna position. It is mainly dependent on the pulse length, antenna height and location, ownship structure and an efficient transmission line.

Maximum range

The maximum range varies considerably depending on several factors such as the height of the antenna above the waterline, the height of the target above the waterline, the size, shape and material of the target, and atmospheric conditions. Under normal atmospheric conditions, the maximum range is equal to the radar horizon and can be slightly longer. The radar horizon is longer than the optical horizon by approximately 6% because of the diffraction property of the radar beam.

  1. Radar horizon (beam).

  2. Blind area.

  3. Ship will not be visible on the display as it is too close and therefore outside of the radar beam.

  4. Ship will be visible on the display as it is within the radar beam.

  5. Ship may be visible on the display as it is only just outside of the radar beam.

  6. Ship will not be visible on the display as it is too far and therefore outside of the radar beam.