Which of the following is true about the accuracy of GPS positioning if RAIM is lost?

When RAIM (Receiver Autonomous Integrity Monitoring) is lost, the reliability of GPS positioning is significantly affected. RAIM's primary function is to ensure the integrity of the GPS signals being received by the aircraft. It detects any anomalies in the satellite signals caused by factors such as satellite failure or errors, thereby providing a level of confidence in the accuracy of the position information.

Without RAIM, there is no mechanism to monitor the integrity of the GPS signals, which means that the system is unable to verify that the positioning data it provides is accurate. As a result, the reliability of the positioning can degrade, which could potentially lead to navigation errors. This situation poses significant risks, especially in precision navigation scenarios where accurate positioning is crucial.

While some level of positioning may still be available, the lack of integrity monitoring suggests that the accuracy and reliability of that positioning can no longer be guaranteed. Therefore, the correct assessment is that GPS positioning becomes less reliable when RAIM is lost.