Definition
A digital elevation model is a computer dataset that stores the height of the Earth's surface at a regular grid of points across a geographic area. In avionics, the DEM is the underlying terrain database that a Synthetic Vision System (SVS) uses to draw the three-dimensional picture of mountains, hills, and ground features on the cockpit display.
Plain English
A digital map of how high the ground is at every point in an area. The aircraft's display software reads this data to draw a realistic picture of the terrain ahead.
Context Anchor
Seen in synthetic vision system discussions, where stored terrain data is used to create a cockpit display that looks like the outside world.
Derivation
Digital means stored as numbers in a computer. Elevation means height above a reference (usually mean sea level). Model means a representation of something real. Together: a numeric representation of ground height.
Why Pilots Care
It enables the display of accurate terrain in synthetic vision, reducing the risk of flying into mountains or hills in low visibility.
Analogy
Think of a DEM like a map made of many tiny squares, where each square has a height number written on it. The system uses those height numbers to build the terrain picture.
Grounding Statement
When the display shows a ridge ahead, the DEM is the stored height information that helps place that ridge in the right position and at the right height.
Intuition Check
A DEM is not a photograph of the ground. It is height data that the aircraft’s system uses to build a terrain picture.
Example Sentence 1
The synthetic vision display uses a digital elevation model to render the ridgeline ahead of the aircraft.
Example Sentence 2
Pilots can reference the DEM data to better understand elevation changes along their flight path.