What is selective availability in GPS?

What is selective availability in GPS?

• A. The deliberate degradation of the GPS signal
• B. Encryption of signals for authorized users
• C. The universal time reference for navigation
• D. Scheduling of satellite maintenance windows

Answer: (A)

Selective Availability means the deliberate degradation of the GPS signal to limit civilian accuracy. This was done by the U.S. military by intentionally distorting the civilian C/A signals, adding controlled errors to the pseudorange measurements that civilians rely on. The result was positions that were much less precise for non-authorized users while those with access to the encrypted military signals could still achieve higher accuracy. This policy was turned off in 2000, so modern GPS no longer implements SA, but understanding it helps explain why signals could be restricted and how encryption and access control relate to navigation systems. The other options refer to encryption, the time reference, or maintenance scheduling, which are not what selective availability describes.

Selective Availability means the deliberate degradation of the GPS signal to limit civilian accuracy. This was done by the U.S. military by intentionally distorting the civilian C/A signals, adding controlled errors to the pseudorange measurements that civilians rely on. The result was positions that were much less precise for non-authorized users while those with access to the encrypted military signals could still achieve higher accuracy. This policy was turned off in 2000, so modern GPS no longer implements SA, but understanding it helps explain why signals could be restricted and how encryption and access control relate to navigation systems. The other options refer to encryption, the time reference, or maintenance scheduling, which are not what selective availability describes.