RAIM is used to verify the usability of which signals?

• A. GPS signals
• B. VOR signals
• C. DME signals
• D. ADF signals

Answer: (A)

RAIM, or Receiver Autonomous Integrity Monitoring, is used to verify the usability of GPS signals. It checks the consistency of measurements from multiple satellites to detect any faulty satellite or degraded signal that could lead to an incorrect position. By comparing redundant satellite data, the receiver can identify when one satellite’s measurements don’t align with the others and flag the GPS solution as unreliable if needed. This integrity check is essential for navigation and approaches that depend on GPS. Other navigation aids like VOR, DME, or ADF have their own operation principles and are not evaluated with RAIM, which is specific to GPS. Typically, enough satellites are required to perform RAIM and isolate a faulty signal, guaranteeing that the remaining satellites provide a trustworthy position.