What is the primary function of WAAS?

The primary function of the Wide Area Augmentation System (WAAS) is to relay corrections and integrity messages from ground stations to improve the accuracy of GPS signals used for navigation. WAAS provides enhanced precision, which is essential for aircraft navigation and landing, particularly in areas where GPS signals may be less accurate due to various factors such as atmospheric conditions or signal interference.

The system consists of a network of ground reference stations that monitor GPS signals and calculate corrections for signal errors. These corrections are then transmitted to geostationary satellites, which in turn broadcast the corrected signals back down to users on the ground, including aircraft equipped with WAAS-capable GPS receivers. This results in improved positional accuracy, allowing for more precise navigation and approach capabilities.

The other choices focus on functions that WAAS does not perform. For instance, while WAAS enhances GPS signals, it does not directly communicate with pilots during flight in the way that air traffic control communication does. Additionally, controlling aircraft movement on the ground and facilitating air traffic control communication are tasks typically managed by other systems and operational procedures, rather than by WAAS itself. This distinction solidifies the role of WAAS as primarily a system for enhancing GPS accuracy through correction and integrity messages.