Below link news dated on Jan 2018 is about that The US Navy restarted training in celestial navigation and sextant use due, in part, to concerns about GPS jamming. https://www.sail-world.com/news/200790/US-Navy-Sextant-Decision-wise-for-anyone-offshore Digital Sextant is free from GPS and when lost signal on sailing, this is an essential device for safety by checking the vessel's position.