determine  the  accurate  ranges  and  bearing  of  surface targets  and  low-flying  aircraft. The  following  are  some  applications  of  surface search radars: Indicate the presence of surface craft and aid in determining  their  course  and  speed Coach fire control radar onto a surface target Provide security against attack at night, during conditions of poor visibility, or from behind a smoke  screen Aid in scouting Obtain   range   and   bearing   on   prominent landmarks  and  buoys  as  an  aid  to  piloting, especially  at  night  and  in  conditions  of  poor visibility Facilitate  station  keeping Detect  low-flying  aircraft Detect  certain  weather  phenomena Detect  submarine  periscopes Aid in the control of small craft during boat and amphibious   operations Navigation  radars  fall  into  the  same  general category as surface search radars. As the name implies, navigation radars are used primarily as an aid to navigate or pilot the ship. This type of radar has a shorter operating range and higher resolution than most surface search  radars.  Because  the  navigation  and  surface search   radars   share   the   same   general   operating characteristics,  both  radar  types  can  be  used simultaneously with one covering longer ranges, while the other covers distances closer to the ship. The use of radars for navigation is discussed further in  Electronics Technician, Volume 5—Navigation. So now, with surface search and navigation radars on line, the ship is aware of all surface targets, land masses, and low-flying aircraft. But, to protect itself from fighter planes, incoming missiles, and other targets in the upper skies, the ship requires a different type of radar. Air Search The primary function of an air search radar is to maintain a 360-degree surveillance from the surface to high altitudes and to detect and determine ranges and bearings of aircraft targets over relatively large areas. The following are some applications of air search radar: Early  warning  of  approaching  aircraft  and missiles,  providing  the  direction  from  which  an attack could come. This allows time to bring anti-aircraft defenses to the proper degree of readiness and to launch fighters if an air attack is imminent. Constant  observation  of  movement  of  enemy aircraft, once detected, to guide combat air patrol (CAP)  aircraft  to  a  position  suitable  for  an intercept Provide security against attacks at night and during times of poor visibility Provide  information  used  for  aircraft  control during operations requiring a specific geographic track (such as an anti-submarine barrier or search and rescue pattern) Together,  surface  and  air  search  radars  provide  a good early warning system. However, the ship must be able to determine altitude to effectively intercept any air target. This requires still another type of radar. Height  Finding The  primary  function  of  a  height-finding  radar (sometimes referred to as a 3D or three-coordinate radar) is to compute accurate ranges, bearings, and altitudes  of  targets  detected  by  air  search  radar.  This information is used to direct fighter aircraft during interception of air targets. The  height-finding  radar  is  different  from  the  air search  radar  in  that  it  has  a  higher  transmitting frequency,  higher  output  power,  a  much  narrower vertical beamwidth, and requires a stabilized antenna for altitude accuracy. The   following   are   some   applications   of height-finding  radar: Obtain  range,  bearing,  and  altitude  data  on enemy  aircraft  and  missiles  to  assist  in  the guidance of CAP aircraft Provide  precise  range,  bearing,  and  height information   for   fast   and   accurate   initial positioning of fire control tracking radars Detect  low-flying  aircraft 1-7