GPS is affected by weather?

• A. It is affected by weather
• B. It is affected only by severe weather
• C. It is not affected by weather
• D. It is affected by solar activity only

Answer: (C)

GPS signals come from satellites in space, so ordinary weather in the atmosphere doesn’t directly block or erase the signals. The main sources of GPS error are things like the satellite clock and orbit information, and atmospheric delays (ionosphere and troposphere) or local multipath near the receiver. These atmospheric effects are well modeled and corrected in modern receivers, and the impact of typical weather (like clouds or rain) on the L-band GPS signals is minimal. Solar activity can influence the ionosphere, but that’s separate from weather and isn’t what pilots mean by weather conditions affecting GPS. So, in normal aviation use, GPS isn’t considered to be affected by weather in the way other navigation aids can be.