Interpreting the radar display ContentsInterpreting objectsThe 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.Radar rangeRadar image qualityA number of factors may impact the quality of a radar image.Blind sectorsObstructions such as funnels and masts near the radar antenna may obstruct the radar beam and cause radar shadows or ‘blind sectors’.False echoesAny large obstruction may reflect the radar beam, causing false echoes. The surface of the obstruction reflects a significant proportion of the transmitted energy at an angle, creating a false echo. Reflected signals from these objects reach the antenna and are presented on the bearing at which the antenna is pointing. The range of the false echo is the same distance (via the reflecting surface) of the object causing the false echo. It is also possible to have multiple false echoes at equal distances.Target smearingWhere obstructions occur in close proximity to the antenna, the radar beam may be dispersed causing target smearing to occur.Multi-path interferenceThe radar beam can reflect back directly from the target or from a sea surface reflection of the target. When this multi-path interference occurs, the two signals will either reinforce one other or cancel each other out, creating a null.Radar interferenceInterference from other radar scanners operating in the area is shown on the screen as irregular, curved, spoke-like patterns extending from the center to the edge of the radar image.Atmospheric conditionsRadar signals can be adversely impacted by poor atmospheric conditions.Reflectors and beaconsTarget Detection in clutter conditionsNext topic: Licensing issuing authorities