The fundamental weakness of GPS and similar is that they are a set of beacons from which a position may be calculated. This has simplified the navigation task b

The fundamental weakness of GPS and similar is that they are a set of beacons from which a position may be calculated. This has simplified the navigation task but also made that task more fragile. Navigation itself must "toughen up" and the seeds for that are being deployed to autonomous systems as simultaneous localization and mapping (SLAM). Instead of being dependent on a single data source, a toughened system would infer location from many sources: magnetometers, photogrammetry, inertial measurement, and other sources of radiation (ex star trackers). The article does cover some developments in these areas as a second line after advocating for breaking changes to the current radio-time system. GPS jamming and spoofing will not abate anytime soon. The first line of defense is to crosscheck GPS PNT against inputs from other sensors. Parkinson advocates “deep integration,” or close coupling, of GPS sensors and inertial reference platforms, such as laser, fiberoptic gyros and microelectromechanical gyros and accelerometers, to flag obvious GPS signal interference.