JRC JMA-5206 Instruction Manual page 284

Height of Radar Scanner
When the height of own ship's scanner is 10 m for instance,
(a) A target that can be detected at the radar range of 64 nm on the radar display is required to have a height
of 660 m or more.
(b) If the height of a target is 10 m, the radar range has to be approx. 15 nm. However, the maximum
radar range at which a target can be detected on the radar display depends upon the size of the target
and the weather conditions, that is, the radar range may increase or decrease depending upon those
conditions.
D (nm)
Detective Range
Figure 6.1
6─3
Height of Target