Ground speed refers to the speed at which an aircraft or vehicle moves relative to the ground. It is an important measurement in aviation, as it helps pilots understand how quickly they are traveling over the Earth's surface. Ground speed can be affected by factors such as wind direction and speed, which can either increase or decrease the actual speed over the ground compared to the speed indicated by the aircraft's instruments. In aviation, ground speed is typically measured in knots or miles per hour. Pilots use this information for navigation and to calculate arrival times at their destination. Understanding ground speed is crucial for flight planning and ensuring safety during takeoff and landing, especially when considering the effects of wind and weather conditions.