Model Perspective

Dec 21, 2025 · Fundamentals

Why Did Nanjing’s GPS Fail? Unveiling the Math Behind Satellite Navigation

On December 17, 2025, a massive GNSS signal disruption in Nanjing caused major navigation apps to fail, prompting a technical analysis that reveals how trilateration, pseudorange measurements, linearization, least‑squares solving, and error factors like GDOP and carrier‑phase ambiguity underpin modern satellite positioning.