- scanning
- In radar, the motion of the radar antenna assembly when searching for targets. Scanning usually follows a systematic pattern involving one or more of the following:i. In horizontal scanning (or search lighting), the antenna is continuously rotated in an azimuth around the horizon or in a sector (sector scanning). This is used to find the azimuth of the targets and generate plan-position-indicator-scope displays.ii. Vertical scanning is accomplished by holding the azimuth constant but varying the elevation angle of the antenna. It is used in height-finding radars to generate the relative-height-indicator-scope display.iii. For conical scanning, a somewhat off-center radiating element is rotated while its parabolic reflectors remain fixed in position, so that the radiated beam generates a conically shaped volume with the antenna at the apex. It is used to determine an accurate bearing and the elevation angle of targets and is employed in automatic-tracking radars.iv. In helical scanning (or spiral scanning), the azimuth and the elevation angle of the antenna are constantly varied, so that at a given distance from the radar the radiated beam generates the surface of a hemisphere. It is used for radio direction finding, in certain types of search radars, and in tracking radars to search areas for targets. See sector scan, conical scanning, helical scan, and height-finder radar.
Aviation dictionary. 2014.