What is the function of a transponder in aviation?

The function of a transponder in aviation is to transmit the aircraft's identity, altitude, and other relevant data to ground radar and air traffic control systems. A transponder serves as an essential tool for enhancing situational awareness in the airspace, allowing air traffic controllers to track aircraft and manage air traffic effectively. When an aircraft is approaching or within controlled airspace, the transponder's signal, which includes a specific squawk code identifying the aircraft, helps controllers maintain safe distances between planes and aids in collision avoidance.

In contrast, the other options do not accurately describe the primary function of a transponder. GPS navigation is a different system that helps determine the aircraft's position, but it does not provide identity or altitude data to radar. Communication with other pilots may occur via radio systems, which is separate from the transponder's function. Lastly, measuring aircraft speed is primarily the role of airspeed indicators and not the transponder, which focuses on altitude and identification signals. Understanding this helps clarify the specific role each component plays in aviation safety and navigation.