Navigational radars resemble search radar, but use very short waves that reflect from earth and stone. They are common on commercial ships and long-distance commercial aircraft. Marine radars are used by ships for collision avoidance and navigation purposes. The frequency band of
radar used on most ships is
X band (9 GHz/3 cm), but
S band (3 GHz/10 cm) radar is also installed on most oceangoing ships to provide better detection of ships in rough sea and heavy rain condition.
Vessel traffic services also use marine radars (X or S band) for tracking
ARPA and provides collision avoidance or traffic regulation of ships in the surveillance area. General purpose radars are increasingly being substituted for pure navigational radars. These generally use navigational radar frequencies, but modulate the pulse so the receiver can determine the type of surface of the reflector. The best general-purpose radars distinguish the rain of heavy storms, as well as land and vehicles. Some can superimpose sonar and map data from
GPS position.
Air Traffic Control and navigation Air traffic control uses primary and secondary radars. Primary radars are a "classical" radar which reflects all kind of echoes, including
aircraft and clouds. Secondary radar emits pulses and listens for special answer of digital data emitted by an Aircraft
Transponder as an answer. Transponders emit different kind of data like a 4 octal ID (mode A), the onboard calculated altitude (mode C) or the Callsign (not the
flight number) (mode S). Military use transponders to establish the nationality and intention of an aircraft, so that air defenses can identify possibly hostile radar returns. This military system is called IFF (
Identification Friend or Foe). •
Air Traffic Control (ATC) Radars •
Secondary Surveillance Radar (SSR) (Airport Surveillance Radar) • Ground Control Approach (GCA) Radars •
Precision Approach Radar (PAR) •
Distance Measuring Equipment (DME) •
Radio Beacons •
Radar Altimeter (RA) •
Terrain-Following Radar (TFR) Space and range instrumentation radar systems • Space (SP) Tracking Systems • Range Instrumentation (RI) Systems • Video Relay/Downlink Systems •
Space-based radar •
Incoherent scatter == Mapping radars ==