The Department of Homeland Security is working with vital national industries to figure out what they could use as an alternative if satellite-based GPS stops working. In a federal register notice published last week, the department announced the launch of a study “to define and validate current and future positioning, navigation, and timing [or PNT] requirements for critical infrastructure.” Vital U.S. industries have become reliant for PNT data, the notice said, on GPS — which is “susceptible to both unintentional and intentional disruption leaving critical infrastructure vulnerable to operational impacts.” DHS studying alternatives to GPS for vital sectors