This week’s episode is a part one of two on PNT – positioning, navigation, and timing. All three parts come from the space-based Global Positioning System, or GPS. Anything from precision farming and guided missiles, and the operational synchronization of critical infrastructures like dams and refineries depends on GPS. Thing is, if something goes wrong, there’s no “plan B”. Laura Winter speaks with Dana Goward, a retired Coast Guard captain, who’s now serving on the National Positioning, Navigation and Timing Advisory Board, and president of the Resilient Navigation and Timing Foundation.