Definition
ASDE-3 is a high-resolution ground surveillance radar installed at major airports to detect and display the position of aircraft and vehicles on the airport surface. It provides controllers in the tower with a continuous radar picture of runways, taxiways, and ramp areas, including during periods of darkness, fog, rain, or other low-visibility conditions when direct visual observation from the tower is degraded or impossible.
Plain English
A radar designed to watch what is moving on the ground at the airport. It shows the tower controller where aircraft and vehicles are on the runways and taxiways, even when they cannot see them out the window because of weather or darkness.
Context Anchor
You may see this term in AIM glossary material, tower and ground-control discussions, or information about operations at larger airports during poor visibility.
Derivation
Radar comes from 'radio detection and ranging' — using radio waves bounced off objects to find where they are. ASDE applies that same idea, but pointed downward and outward across the airport surface instead of up into the sky. The '3' simply indicates the third generation of the equipment.
Why Pilots Care
Reduces the risk of runway incursions and ground collisions by giving controllers real-time location data when visual contact is limited.
Intuition Check
Do not think of ASDE-3 as radar in the airplane. It is airport equipment used by controllers to watch surface traffic.
Example Sentence 1
In dense fog, the tower controller used ASDE-3 to track our taxi route from the ramp to runway 27.
Example Sentence 2
ASDE 3 allowed ground control to track multiple vehicles on the taxiways during a nighttime operation.