Plain English Meaning

Satellites that hover over the same spot on Earth because they orbit at the same speed Earth spins. WAAS uses them to send GPS correction signals down to aircraft.

Full Definition

Satellites placed in orbit approximately 22,236 miles above the equator, where their orbital period matches the Earth's rotation. As a result, each satellite remains over the same point on the Earth's surface at all times. In the WAAS system, geosynchronous satellites broadcast GPS correction and integrity data to aircraft receivers within their coverage footprint.

Context Anchor

Seen in WAAS and GPS navigation discussions, especially when explaining how WAAS correction information reaches the aircraft.