What advantage does the GPS have when used with the satellite-based augmentation system (SBAS)?

The correct answer highlights that the integration of GPS with a Satellite-Based Augmentation System (SBAS) enhances its capabilities, particularly making it suitable as a standalone primary navigation source for enroute and approach operations.

GPS on its own provides positioning information, but when combined with SBAS, users benefit from improved accuracy, integrity, and reliability. SBAS systems, such as WAAS (Wide Area Augmentation System), correct for errors in satellite signals caused by atmospheric conditions, satellite orbit inaccuracies, and timing discrepancies. This correction enables pilots to have precise position data, which is crucial for safe navigation, especially during approaches to airports where safety margins are narrower.

This capability makes GPS coupled with SBAS more reliable than standard GPS alone, justifying its use as a primary navigation tool in aviation settings. The accuracy and integrity assurances of SBAS-deployed GPS meet the mandated requirements for various phases of flight, including enroute and approaches, thus enhancing operational safety and efficiency.