At the most recent National PNT Advisory Board meeting Dr. Gene McCall, former Chairman of the Air Force Scientific Advisory Board, called for the nation to focus on PNT services instead of systems.  By doing that, he said, we would realize that a combination of systems are needed to make our essential PNT services more accurate and more resilient.

His presentation was based upon a paper “Assured Positioning, Navigation, and Timing for the United States” he published late last year with the American Center for Democracy.

Here is a link to his presentation in which he advocates a GNSS/INS/eLoran resilience triad.