Definition
A stored digital record of ground elevations and obstacle heights, organized by geographic position, that onboard avionics use to determine the height of terrain and obstructions relative to the aircraft. It is referenced by systems such as the Terrain Awareness and Warning System (TAWS), synthetic vision, and autoland to provide alerts, displays, and protected flight paths.
Plain English
An onboard map of how high the ground and tall obstacles are everywhere the aircraft might fly. The avionics check the airplane's position against this stored map to know what is below and ahead.
Context Anchor
Seen in avionics and autoland discussions where the airplane uses stored ground information to help display, alert, or guide the flight path near the airport.
Derivation
Terrain' comes from Latin 'terra' meaning 'earth' or 'ground.' A 'database' is an organized collection of stored information. Together: stored information about the ground.
Why Pilots Care
Allows automated systems to detect and avoid terrain conflicts during approach and landing.
Analogy
It is like having an offline map saved in your car’s navigation system. The system can compare where you are with the roads and hills it has stored, but only if the saved map is correct and current.
Intuition Check
Do not think of a terrain database as the airplane looking outside and measuring the ground in real time. It is stored information that the aircraft system uses along with the airplane’s known position.
Example Sentence 1
Before the flight, the crew confirmed the terrain database was current so the synthetic vision display would show accurate ground and obstacle heights.
Example Sentence 2
Before departure the crew confirmed the terrain database was up to date for the destination airport.