Which factor related to terrain can block GPS signal?

• A. Banking the aircraft
• B. High terrain
• C. WAAS corrections
• D. RAIM alert

Answer: (B)

High terrain can block GPS signal because GPS needs a clear line of sight to multiple satellites. When mountains or tall ridges sit between the receiver and the satellites, the sky view is obstructed, reducing the number of satellites visible and degrading signal reliability. In rugged terrain, you can experience partial or total loss of GPS coverage in canyons or behind peaks, which is why terrain-related obstruction is a real navigational concern. Banking the aircraft doesn’t change the line of sight to satellites, WAAS corrections improve accuracy but don’t remove terrain blockages, and a RAIM alert indicates integrity concerns rather than a physical blockage by terrain.