Definition
A radio wave that travels along the surface of the Earth, following its curvature, rather than radiating into the sky. Ground waves are most effective at low and medium frequencies and are used by navigation aids such as the NDB (Non-Directional Beacon).
Plain English
A radio signal that hugs the ground as it travels, bending with the Earth's curve instead of going straight out into space.
Context Anchor
Seen in instrument flying and radio navigation discussions, especially when learning how some navigation beacons send signals to aircraft.
Derivation
Plain English: 'ground' meaning the Earth's surface, and 'wave' meaning a radio wave. The name describes how the signal travels — along the ground rather than through the upper atmosphere.
Why Pilots Care
It determines how far low-frequency navigation beacons can be received, directly affecting ADF usable range and enroute navigation planning.
Analogy
Like water ripples that follow the contour of a pond bottom instead of flying off in a straight line.
Grounding Statement
Picture a radio signal spreading outward from a beacon while staying close to the Earth’s surface instead of shooting straight up into the sky.
Intuition Check
A ground wave is not a wave in the dirt or a movement of the ground. It is radio energy traveling close to the Earth’s surface.
Example Sentence 1
The NDB signal reaches the aircraft via ground wave, which is why it remains usable even at low altitudes.
Example Sentence 2
At night the pilot noted reduced ground-wave range on the low-frequency beacon and switched to a closer aid.