既然北斗系统这么准，为什么有时开车到立交桥，手机导航突然就跟不上了？ 这个问题非常典型。北斗系统在天上提供稳定、精准的信号源，但立交桥复杂环境的物理结构像一 个"锅盖"，暂时扣住了这些信号，而北斗系统本身的高精度特性有时反而会放大这种瞬间的定位数据波 动。手机在"失明"的几秒钟内，靠自己"猜测"行进路径，就容易出现跟不上的情况。这并非北斗系统不 准，而是信号被遮住和扰乱了。 当我们开车驶上立交桥时，桥面本身、高大的桥墩以及周边的密集建筑会形成"城市峡谷"，物理遮挡了 手机接收来自北斗等导航卫星的直射信号。手机在瞬间只能接收到少量卫星的反射信号或微弱信号，导 致它无法计算出精确的位置。其次，在立交桥区域，北斗信号可能会在桥面、护栏和车辆之间发生多次 反射。这些"走了弯路"的反射信号与直射信号叠加，会"欺骗"手机，让它误判位置，造成定位在桥上桥 下漂移或滞后。随着地面接收机算法的优化，这种情况会逐步解决。 （人民日报） ...

Group 1 - The core issue discussed is the temporary loss of GPS signal accuracy when driving on overpasses due to physical obstructions like bridges and buildings, which can interfere with satellite signals [1] - The Beidou system provides stable and precise signals, but complex environments can cause momentary disruptions in signal reception, leading to navigation inaccuracies [1] - When vehicles are on overpasses, the physical structures create "urban canyons" that block direct signals from satellites, resulting in reliance on weaker reflected signals that can mislead the device [1] Group 2 - The article highlights that the Beidou system's high precision can sometimes amplify the fluctuations in positioning data during signal loss, causing further confusion in navigation [1] - It mentions that as ground receiver algorithms improve, the issues related to signal reflection and misjudgment of location will gradually be resolved [1]