GNSS such as GPS and Galileo (under development by the EU) are primarily intended for navigation and location, but also provide a global system for extremely accurate time and frequency information.

• 利用全球巡航卫星系统（GNSS），如GPS或伽利略（由欧盟开发）系统，主要用于导航和定位，也可以提供极其准确的全球时间频率信息。