What is indicated airspeed (IAS)?

Indicated airspeed (IAS) is defined as the speed obtained directly from the airspeed indicator, which measures the dynamic pressure of the air. This measurement is based on the difference between the ambient atmospheric pressure (static pressure) and the pressure created by the airflow over the aircraft (dynamic pressure). The airspeed indicator does not take into account the effects of altitude, temperature, or other atmospheric conditions, making IAS a crucial parameter for pilots during flight operations. It is essential for ensuring that the aircraft remains within safe operating limits, particularly during takeoff and landing phases.

While the other options pertain to various forms of speed measurement, they do not accurately encapsulate what indicated airspeed represents. GPS speed measures ground speed based on satellite data, which can differ from IAS due to wind conditions. The speed relative to the ground accounts for the aircraft's actual movement over the Earth's surface, while corrected speeds consider factors like temperature and pressure to reflect true airspeed (TAS), which is different from IAS.