Interpreting objects

The size of a target appearing on screen is dependent on many factors, and may not be proportional to its actual physical size. Nearby objects may appear to be the same size as distant larger objects. Given adequate radar operator experience, the approximate size of different objects can be determined by the relative size and color / brightness of the echoes.

Interpreting objectsThe size of onscreen targets are impacted by:

  • The physical size of the reflecting object.

  • The material that the object is made from (metallic surfaces reflect signals better than non-metallic surfaces).

  • The verticality of the object (objects such as cliffs reflect signals better than sloping objects such as sandbanks).

  • The height of costal regions. (High coastlines and mountainous coastal regions can be observed at longer radar ranges; therefore, the first sight of land may be a mountain several miles inland from the coastline. Although the coastline may be much nearer, it may not appear on the radar display until the vessel is closer to shore.)

  • The target’s reflective visibility. (Some targets, such as buoys and small vessels, are difficult to discern because they do not present a consistent reflecting surface as they pitch and roll in the waves. Consequently, these echoes tend to fade and brighten, and at times disappear momentarily.)

  • Similarly-sized targets. (Buoys and small vessels resemble each other; however, vessels can often be distinguished by their motion.)