Core Viewpoint - The article discusses the navigation signal anomalies that occurred in Nanjing on December 17, 2025, emphasizing the technical reasons behind the issue and the strategic significance of the BeiDou and GPS systems' compatibility. Group 1: Navigation Signal Anomaly - The navigation failure was primarily due to temporary interference suppressing GNSS satellite signals (including BeiDou and GPS), rather than a network signal interruption, making offline maps ineffective [3][4]. - Offline maps only store geographic data and cannot replace the positioning signal source, as mobile navigation relies on GNSS signals from at least four satellites to calculate location coordinates [4]. Group 2: Strategic Significance of BeiDou and GPS Compatibility - The simultaneous impact on both BeiDou and GPS signals during the anomaly validates the strategic foresight of China's BeiDou system's civilian frequency planning [5][6]. - The compatibility of BeiDou's civilian signal (B1C frequency) with GPS's civilian signal (L1C frequency) allows for interoperability, creating a strategic balance where interference with BeiDou also affects GPS, thus deterring malicious disruptions [6]. Group 3: Military Frequency Resilience - The signal anomaly only affected civilian GNSS frequencies, while BeiDou's military frequency remained unaffected due to its separation from civilian frequencies [7]. - BeiDou's military system employs advanced anti-jamming technologies, ensuring robust resistance to interference and maintaining reliable time-space services for national defense and emergency support [7].

Core Viewpoint - The core reason for the navigation failure in Nanjing on December 17 is the temporary interference suppression of GNSS satellite signals (including Beidou and GPS), rather than a network signal interruption, making offline map downloads ineffective [1][7]. Group 1: Technical Analysis - Offline maps only store geographic data and cannot replace the source of positioning signals, which rely on GNSS satellite signals to calculate location coordinates [9]. - The interference specifically targeted the civilian frequency bands of Beidou and GPS, preventing the positioning signals from being recognized by receivers, leading to issues like positioning drift and lack of data feedback even with offline maps [9]. - Offline maps are more suitable for areas with satellite positioning signals but without communication network signals, such as oceans, deserts, and mountains [9]. Group 2: Strategic Significance of Frequency Compatibility - The simultaneous impact on both Beidou and GPS signals during this incident validates the strategic foresight of China's Beidou system in planning civilian frequency bands [10]. - The international satellite navigation spectrum resources follow a "first come, first served" rule, with GPS having occupied core L-band resources early on, leaving limited quality spectrum for Beidou [10]. - The compatibility of Beidou's civilian signal (B1C band) with GPS's civilian signal (L1C band) not only breaks the spectrum resource blockade but also creates a strategic balance where interference with Beidou also affects GPS applications [10]. Group 3: Military Frequency Resilience - The signal anomaly only affected civilian GNSS frequency bands, while the military frequency of Beidou remained completely unaffected [11]. - Beidou employs a military-civilian frequency separation design, with military frequencies being exclusive and physically isolated from civilian bands [11]. - The military system incorporates advanced anti-jamming technologies and adaptive filtering algorithms, enabling it to accurately identify and filter out interference signals, thus maintaining strong anti-jamming and anti-deception capabilities [11].