LOCO GPSI: preserve the GPS advantage for defense and security

Global positioning system (GPS) has clearly emerged as a fundamental utility with widespread private and commercial civilian applications. Many of these applications are directly related to safety-of-life uses such as all-weather aircraft precision approach and landing, ship navigation in restricted waters, and emergency response vehicle tracking and management. GPS has significantly improved efficiency in commercial applications such as truck, train, and even, individual container tracking and dispatch. There is a similar dependency within the military - not only in vehicle navigation ut also in areas such as precision weapon guidance and "blue force" tracking. This dependency on GPS has brought significant attention on the potential for an asymmetric vulnerability on this low signal power radio navigation system. Threat systems to GPS exist, are commercially available, and have been used in combat. The technology is not complex, and even simple, low-cost systems could cause significant GPS denial. Furthermore, as other global navigation satellite systems gain maturity and widespread use, one can easily imagine the threat expanding to cover those systems as well. Herein, we describe a project directed by Congress, starting in 1997, to develop the capability to detect and locate sources of unintentional interference and intentional jamming, and to assess the effectiveness and utility of such a system. Under this project, SPAWAR and FALON, Inc. have successfully developed and demonstrated a prototype system small enough to be compatible with unmanned aerial vehicles named location of GPS interferers (LOCO GPSI). The LOCO GPSI system employs short baseline antenna interferometry and a highly sensitive, rapidly scanning receiver to detect and precisely direction find (DF) the interference source. Interference source location is determined by triangulating successive DF lines of position. Ground and flight demonstration results suggest that performance objectives have been met.