Scanning

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Scanning

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In radar, the motion of the radar antenna assembly when searching for targets. </dd>
Scanning usually follows a systematic pattern involving one or more of the following: (1) In horizontal scanning (or searchlighting), the antenna is continuously rotated in azimuth around the horizon or in a sector (sector scanning); used to generate plan-position-indicator-scope displays. (b) Vertical scanning is accomplished by holding the azimuth constant but varying the elevation angle of the antenna; used in height-finding radars to generate the relative-height-indicator-scope display. (c) For conical scanning, a somewhat offcenter radiating element is rotated while its parabolic reflectors fixed in position so that the radiated beam generates a concially shaped volume with the antenna at the apex; used to determine accurate bearing and elevation angle of targets and employed in automatic tracking radars. (d) In helical scanning (or spiral scanning) the azimuth and 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; used for radio direction finding, in certain types of search radars, and in tracking radars to search areas for targets. </dd>

References

This article is based on NASA's Dictionary of Technical Terms for Aerospace Use