01	Acoustic Detection and Detectors	Detection by means of acoustic waves, including infrasonic, sonic and ultrasonic waves; Sonar detection. For underwater sound transmission studies, See 20/01, Acoustics. For acoustic countermeasures, See 17/04/02, Acoustic Countermeasures. For acoustic holography, See 14/01, Holography. See also 17/10, Seismic Detection and Detectors.
02	Non-acoustic and Non-magnetic Submarine Detection	The detection of submarines by means other than acoustic or magnetic.
03	Direction Finding	Determination of the direction of arrival of signals. For target direction finding, see the appropriate group in Field 17, Navigation, Detection and Countermeasures. For determining one's own position or direction, See 17/07, Navigation and Guidance.
04	Countermeasures	Interception, jamming and antijamming, and deception of signals other than radio, radar, optical and acoustic; Applicable counter countermeasures. For countermeasures against directed energy weapons, See 19/12, Directed Energy Weapons. For underwater countermeasures, See 19/08, Underwater Ordnance, and 19/08/01, Torpedoes.
04/01	Radio Countermeasures	Interception, jamming and antijamming, and deception of radio signals; Applicable counter countermeasures. For radio communications, See 25/02, Radio Communications.
04/02	Acoustic Countermeasures	Interception jamming and antijamming, and deception of acoustic signals; Applicable counter countermeasures. For acoustic detection, See 17/01, Acoustic Detection and Detectors.
04/03	Radar Countermeasures	Interception. jamming and antijamming, and deception of radar signals, chaff; Applicable counter countermeasures. For radar homing and navigation,See 17/07, Navigation and Guidance. For radardetection, See 17/09, Active and Passive Radar Detection and Equipment.
04/04	OpticalCountermeasures	Interception,jamming and antijamming, and deception of optical signals; Electroopticsto nullify use of optical systems; Applicable counter countermeasures.Includes infrared, ultraviolet and laser countermeasures. For opticaldetection, See 17/05, Optical Detection and Detectors.
05	Optical Detection and Detectors	Detection by means of visible light or light of unspecified frequency; Electronic detectors of light waves. Includes such optical instruments as binoculars and periscopes. For infrared detection, See 17/05/01, Infrared Detection and Detectors. For ultraviolet detection, See 17/05/02, Ultraviolet Detection and Detectors.
05/01	InfraredDetection and Detectors	Detectionby measurement of infrared radiation. Includes optical instrumentsWhich detect infrared radiation. For infrared photography, See 14/04, Photography.
05/02	Ultraviolet Detection and Detectors	Detection by measurement of ultraviolet radiation. Includes optical instruments which detect ultraviolet radiation.
06	Magnetic and Electric Field Detection and Detectors	Detection by measurement of magnetic or electric fields. For natural geomagnetic phenomena, See 08/04, Geomagnetism.
07	Navigation and Guidance	Navigation and guidance theory, analysis, design methodology, techniques, procedures and systems. For navigation on land, bodies of water, underwater, in air or space, See 17/07/01, Land and Riverine Navigation and Guidance; 17/07/02, Underwater and Marine Navigation and Guidance; 17/07/03, Air Navigation and Guidance; and 17/07/04, Space Navigation and Guidance, respectively.
07/01	Land and Riverine Navigation and Guidance	Navigation and guidance of surface craft and water. Includes navigating and guiding vehicles on land, rivers and small bodies of planetary surface exploratory vehicles. For surveying to determine one's own position underground, See 13/02, Civil Engineering.
07/02	Underwater and Marine Navigation and Guidance	Navigation and guidance of ships, submarines, submersibles, and underwater vehicles in the oceans and other large bodies of water. For torpedo guidance, See 19/08/01, Torpedoes.
07/03	Air Navigation and Guidance	Navigation and guidance of aircraft, missiles, remotely piloted vehicles and drones. Includes air traffic control systems, controlled approach systems, and instrument landing systems. For navigation by animals, See 06/03, Biology. For aircraft onboard navigation display systems, See 01/04, Flight Control and Instrumentation.
07/04	Space Navigation and Guidance	Navigation and guidance of manned and unmanned spacecraft and vehicles. For the navigation and guidance of planetary surface exploratory vehicles, See 17/07/01, Land and Riverine Navigation and Guidance.
08	Miscellaneous Detection and Detectors	Includesdetection by biological and chemical means. For nuclear radiation detection, See 18/04, Nuclear Instrumentation. For detection of CBR agents, See 15/06/03,Chemical, Biological and Radiological Warfare.
09	Active and Passive Radar Detection Equipment	Detection by means of reflected Radar Detection and radiofrequency waves. Includes passive radar and microwave radiometry. For optical radar, See 17/05, Optical Detection and Detectors, or 17/05/01, Infrared Detection and Detectors. For radar signal interception, See 17/04/03, Radar Countermeasures. For radar mapping, See 08/02, Cartography and Aerial Photography.
10	Seismic Detection and Detectors	Detection by measurement of seismic waves; Seismic intrusion alarms. For studies of natural seismic events, See 08/11, Seismology. For detection of nuclear explosions, See 18/03, Nuclear Explosions and Devices (Non-Military), and 19/11, Nuclear Weapons. For location of mineral deposits by means of seismic waves, See 08/09, Mining Engineering.
11	Target Direction,Range and Position Finding	Determination of the direction, range or position of a target. If the means of detection is known, use the appropriate group in Field 17, Navigation, Detection and Countermeasures. For signal direction finding, See 17/03, Direction Finding.