Definition

The speed of an aircraft relative to the surface of the earth.

Source: ICAO Doc 9426

Relations to Other Speeds

Groundspeed and True Airspeed (TAS)

Groundspeed is a vector sum of True Airspeed (TAS) and wind velocity.

A graphical representation of TAS, wind velocity and ground speed

Groundspeed/TAS and IAS

If an aircraft maintains IAS, TAS (and therefore groundspeed) increases when an aircraft climbs. This is because air density decreases with altitude and consequently, higher speed is required to obtain the same dynamic pressure. As a result, if two aircraft are maintaining the same IAS and tracks at different levels and the wind is the same, the higher aircraft will fly faster in terms of groundspeed.