Royal Academy of Engineering Report
“All satellite-based positioning systems (GNSS) are vulnerable to failure, disruption and interference, and much work has been done to assess the possible failure modes and their effects on services, and to develop strategies to detect failures and correct them.”
This seminal report published in March 2011 by the Royal Academy of Engineering in the UK contains a comprehensive description of the vulnerabilities of space-based positioning systems and cites the urgent need to find Alternative Position, Navigation and Timing (APNT) solutions to provide “Plan B” redundancy for GPS.