卫星导航系统（GNSS）的脆弱性正日益凸显。得克萨斯大学奥斯汀分校托德·汉弗莱斯（Todd Humphreys）团队在6月发表的研究指出，自2019年以来欧洲及其他地区的大范围GPS中断均可追溯至俄罗斯卫星星座，表明来自太空的干扰足以波及整个大洲。由于传统光学地面追踪易受夜间和云雾干扰，科研界正聚焦两大新型替代技术：量子地磁导航（MagNav）与利用环境无线电广播的“机会信号”（signals of opportunity）定位。地磁导航利用地壳岩石磁性分布形成的天然异常场，不受陆地海洋或恶劣天气影响。澳大利亚Q-CTRL公司在新南威尔士州的试飞中展示了光泵磁力仪（OPM），利用激光激发铷原子测定磁场强度；加拿大SBQuantum公司则研发基于金刚石氮-空位（NV）色心的磁力仪，可测定磁场的三维矢量与强度。面对现有地壳磁图精度不足的瓶颈，加州SandboxAQ公司在6月呼吁军民协同绘制全球地磁图，随后美国政府亦下令加码量子传感研发。
另一大突破在于捕获低轨卫星广播信号的多普勒频移（Doppler shifts）。俄亥俄州立大学ASPIN实验室开发的Matrix系统在2024年8月24日格陵兰岛巡航测试中，仅凭21颗过顶的Starlink和OneWeb宽带卫星信号，便将船舶定位误差控制在27米之内。尽管轨道漂移和避障机动常导致多普勒定位出现100米至1公里以上的误差，但SpaceX现已开始公布其1.1万余颗卫星的高精度轨道预测，误差仅在数米之内。在此基础上，弗吉尼亚理工大学的马克·夏基（Mark Psiaki）在交通部资助下引入基准主接收机，通过对比预期与实际频移向盲接收机广播修正参数，有望将多普勒精度提升至10米以内。
夏基博士还通过主接收机实现了信号传输时间测距法：结合基准站已知位置与SpaceX轨道预测反推信号发射时刻，未知位置的接收机即可计算自身与卫星的距离。将4颗星链卫星的测距数据与多普勒频移结合后，定位精度可跃升至2米之内。此外，ASPIN实验室还在与美国空军的测试中成功利用地面蜂窝通信铁塔的微小信号频移引导军机导航。据实验室主管扎克·卡萨斯（Zak Kassas）透露，Matrix系统已授权军民两用客户，商业化套件预计将在两年内正式推向市场，为摆脱传统GPS依赖提供了兼具高精度与抗干扰特性的崭新架构。
The vulnerability of global navigation satellite systems (GNSS) to electronic warfare has become acute. A June 2024 study led by Todd Humphreys at the University of Texas, Austin, traced dozens of extensive GPS disruptions across Europe since 2019 to Russian orbital constellations, proving space-borne jamming can impair entire continents. Consequently, researchers are developing two resilient alternatives: quantum magnetic navigation (MagNav) and "signals of opportunity." MagNav exploits crustal geomagnetic anomalies that persist regardless of darkness, weather, or terrain. Australia’s Q-CTRL successfully demonstrated optically pumped magnetometers using laser-tuned rubidium atoms over New South Wales, while Canada’s SBQuantum developed nitrogen-vacancy diamond magnetometers to capture 3D magnetic vector fields. Addressing inconsistent crustal baseline maps, California's SandboxAQ urged coordinated global magnetic mapping, coinciding with American presidential directives prioritizing quantum sensing applications.
Concurrently, researchers are exploiting Doppler shifts in ambient commercial satellite transmissions. On August 24th, 2024, Ohio State University’s ASPIN Lab tested its Matrix system aboard a vessel off Greenland, processing signals from 21 Starlink and OneWeb low-Earth-orbit satellites to achieve an accuracy of within 27 metres. While orbital drift and collision-avoidance manoeuvres historically caused positioning errors between 100 metres and over one kilometre, SpaceX now publishes orbital trajectories for its fleet exceeding 11,000 satellites accurate to within a couple of metres. Exploiting this telemetry, Mark Psiaki of Virginia Tech deployed stationary master receivers that broadcast empirical frequency corrections to remote units, compressing Doppler positioning error margins to approximately ten metres.
Dr. Psiaki’s master-receiver methodology also enables time-of-flight pseudoranging: by determining the exact transmission timestamp via known receiver coordinates and SpaceX ephemeris data, remote units compute signal transit delays and orbital distances. Combining range calculations from four Starlink satellites with Doppler data refines spatial resolution to just two metres. ASPIN Lab has further adapted the Matrix architecture to navigate military aircraft using cellular phone tower transmissions during Air Force flight trials. With licensing underway across commercial and defense sectors, commercial deployment of these integrated RF-sensing suites is anticipated within two years, establishing robust, jam-resistant navigation independent of conventional GNSS infrastructure.
Source: Alternatives to GPS are around the corner
Subtitle: Earth’s quantum field and signals from other satellites may prove more reliable
Dateline: Oct 1st 2026\n