Which factor primarily limits GPS accuracy?

• A. Weather conditions
• B. The number of satellites
• C. The Earth's rotation
• D. Physical obstructions like mountains

Answer: (D)

Physical obstructions like mountains primarily limit GPS accuracy because the system depends on a clear line of sight to multiple satellites to determine position. When tall terrain blocks the signals, the receiver loses visibility to some satellites and may also pick up reflected signals off the terrain (multipath). These blocked or reflected signals distort the travel-time measurements used to compute distance to each satellite, leading to larger errors in your final position. Weather effects do cause some signal delay as signals pass through the atmosphere, and having more satellites can improve accuracy, but in rugged environments the immediate problem is the obstruction itself.