What type of airspeed indicates an aircraft's speed relative to the earth's surface?

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Ground speed is the measurement that indicates an aircraft's speed relative to the earth's surface. This speed is crucial for various operational aspects of flight, including navigation and estimating arrival times at destinations. Ground speed takes into account the effect of wind; for instance, if an aircraft is flying into a headwind, its ground speed will be less than its true airspeed because the wind is working against it. Conversely, if the aircraft is flying with a tailwind, the ground speed will be greater than the true airspeed.

The other types of airspeed have different definitions and uses. Indicated airspeed is the speed read directly from the airspeed indicator in the cockpit and does not account for air density, while true airspeed represents the actual speed of the aircraft through the air, corrected for altitude and temperature. Vertical speed measures the rate of climb or descent, rather than the horizontal movement across the ground.