Overall Summary: eLORAN: Hybrid GPS LORAN Detect Jamming and Spoofing on GPS Phase I STTR: Hellen Systems (HS) our teaming partner from the University of Massachusetts Lowell (UMass Lowell), we will: 1) Assess the feasibility of using GPS Receiver Autonomous Integrity Monitoring (RAIM) to identify GPS inaccuracies in both timing and navigation solutions due to possible intentional or unintentional Jamming or Spoofing (Phase I). 2) Explore the feasibility of using e-Loran as part of a hybrid GPS solution for operating in the Urban Canyon, combining other sensors with e-Loran and GPS (Phase I). 3) Investigate the feasibility of other commercial and government applications of hybrid e-Loran/GPS receivers for other transportation and commercial timing applications (Phase I). 4) Identify feasible network update methodologies when GPS inaccuracies in both timing and navigation solutions due to possible intentional or unintentional Jamming or Spoofing are identified (Phase I) 5) Identify feasible Receiver update methodologies when GPS inaccuracies in both timing and navigation solutions due to possible intentional or unintentional Jamming or Spoofing are identified (Phase I)