Radar

Radar (Radio Detection and Ranging) is a ground-based system used to detect, locate, and track aircraft by transmitting radio waves and analyzing their reflections. In air traffic control (ATC), radar enables real-time monitoring of aircraft position and movement, forming the backbone of surveillance and separation services.

• Does not rely on aircraft systems
• Detects any object reflecting the radar beam
• Provides azimuth (bearing) and distance, but no altitude or identity
• Used for military, backup, or non-cooperative target detection
• Susceptible to clutter (e.g., weather, terrain)

• Requires aircraft to carry a transponder
• Provides aircraft identity (squawk) and pressure altitude (Mode C)
• With Mode S, also transmits heading, groundspeed, and callsign
• Allows target labeling on controller screens, improving clarity and response

• “Radar contact” → ATC has identified your aircraft on radar
• “Resume own navigation” → Radar vectors are no longer provided
• “Radar service terminated” → Aircraft leaving radar coverage or switching to procedural control

ATC can issue headings to aircraft for sequencing, separation, or traffic avoidance.

Typical instructions include:

• “Turn left heading 210”
• “Fly heading 060 for spacing”

Radar vectoring is common in approach and departure phases, especially in busy terminal areas.

• Squawk Ident → Controller instructs pilot to press IDENT button
• Position correlation → Controller matches position report with radar return
• SSR Code Assignment → ATC assigns a discrete squawk code, linked to flight plan
• Departure correlation → Known time and runway departure allows positive ID

• Line of sight only: Radar coverage depends on aircraft altitude and terrain
• Not all airspace is radar-covered: Especially in mountainous or remote areas
• Radar separation minima must be maintained (e.g., 3–5 NM horizontally, 1,000 ft vertically)

• Traffic sequencing and spacing
• Vectoring for approaches
• Weather avoidance guidance
• Conflict resolution advisories
• Transition between airspace sectors

• Mode S radar networks support enhanced surveillance
• ADS-B and multilateration are augmenting or replacing radar in some FIRs
• Radar screen automation provides data tags showing callsign, level, speed, and intent