Satellite-based navigation has become a ubiquitous tool for business, military and personal use. The downside is that any disruption in the Global Positioning System could wreak havoc down on Earth. This year, the Department of Homeland Security decided that a 30-year-old navigation system used by mariners will be upgraded to back up GPS. The decision preserves the Long-Range Aids to Navigation (LORAN) network, which has been teetering on the verge of forced retirement since the 1980s, according to the Coast Guard’s Navigation Center. The backbone of LORAN is a network of transmission stations, many located in remote regions, staffed with...