The modern battlespace has changed over the past decade, and the military use of GPS to deliver critical positioning, navigation, and timing (PNT) information to warfighters faces challenges from adversaries’ threat systems. GPS continues to be relevant for the U.S. military and its allies, even when used in a GPS-denied environment. Existing and future military GPS solutions must especially consider those uses designed for handheld and ultrasmall applications where size, weight, power, and cost (SWaP-C) are all key considerations.