How can indicated airspeed be determined?

Indicated airspeed (IAS) is directly obtained by measuring from the airspeed indicator located within the cockpit. This instrument displays the air pressure from the pitot tube in relation to static pressure, allowing pilots to read the speed at which the aircraft is moving through the air. The airspeed indicator is calibrated to convert this pressure difference into a speed reading, which does not account for the variations in air density or temperature but rather presents the pilot with the speed based on standard sea level conditions.

Using a GPS device would yield groundspeed, which is the speed over the ground, not the speed through the air. While groundspeed can be useful for navigation, it does not represent the aerodynamic performance of the aircraft. True airspeed is the actual speed of the aircraft through the air and also requires corrections based on altitude and temperature. Therefore, the correct approach to determine indicated airspeed is to rely solely on the airspeed indicator reading.