Securing the GPS

By Dr. Gene H. McCall*
Friday, June 12th, 2015 @ 7:16PM

Print Friendly, PDF & Email

Recently, there has been a considerable interest shown in the fact that the nation has become very dependent on the GPS signals and the capabilities that they enable. There have been many presentations by those who claim that GPS signals are weak enough to provide a significant vulnerability to interference and jamming. Government committees have received briefings on the subject, papers have been presented at professional society meetings.

Many presentations have been oriented toward the establishing of an eLoran system in the U. S. to serve as a backup system if the GPS signal were unavailable. All of the attention to the subject has resulted in what I describe as a sky is falling attitude in some groups. In my opinion, eLoran is an inadequate and obsolete technology that is not, by any stretch of the imagination, a substitute for, or a replacement for the GPS. ELoran is not adequate for precision weapon guidance, or for precision airport approach. If we fall back to eLoran because GPS is not available, we lose those valuable capabilities immediately and they cannot be replaced. Yet, Congressional hearings have been held, and a proposed law (H.R.) 1678, has been submitted to the House of Representatives.

Although I have little knowledge of Congressional rules and procedures, my reading of the resolution gave me the impression that it is a rather curious document. While it is ostensibly about PNT, it gives no required accuracy range for any important PNT parameters. The frequency of the system was, however, specified to be 100 kHz. No price range was mentioned, and there appears to have been no consideration of possible alternatives to eLoran, nor does it indicate that any protective steps for GPS were considered. It also, seems to provide no possibility for competitive bidding. To an old lab worker like me, it appears to be a directive to several government agencies to execute a sole-source purchase request for an eLoran system.

Even if the eLoran signal is assumed to be a suitable replacement for the GPS if the GPS signal is denied, and a signal covering the entire U.S. is supplied, the task of using the signal has just begun. Receivers must be procured. Approximately 2000 will be required to equip several of the major U.S. airline’s aircraft. Also, crews must be trained in the use of the new navaid. The cost may be in the vicinity of 20 million dollars per airline. Given the near mania that airlines have for return on investment (ROI), the airlines may choose to simply cancel flights as a cheaper alternative. The government will have to choose whether to pass legislation mandating that the airlines equip their aircraft with eLoran equipment, or the government will have to supply the airlines with sufficient funds to buy the equipment.

If it is determined that the signal is, indeed, accurate and reliable enough for non-precision approaches, those approaches will have to be designed and certified by the FAA. For 1000 approaches at a typical cost of $50000 per approach, that is a charge to the FAA of 50 million dollars. In total, the charge to the nation is likely to be several billion dollars. The question is: who will pay?

I assume that the task of DHS should be the protection of the nation’s critical infrastructure, not its replacement. Thus, the discussion should be not on how to replace one of the most valuable parts of American infrastructure because it has some weaknesses. While a backup may be part of the discussion, most of the debate should be centered on ways of eliminating the problems of GPS. Now is not the time to retreat to a last century technology because of fears that may be groundless.

When all is considered, protection of the GPS signal is almost certain to be more effective, quicker, and less expensive than attempting to activate a last century PNT system, that will require one, or two decades, at least, to generate even the poor performance advertised for eLoran.

Ultimately, the research and development required to make the GPS invulnerable will benefit the next generation of PNT and will, no doubt, spin off into other fields.

The time to act is passing.

For a detailed discussion on GPS Vulnerability – Options and Alternatives, please see Dr. McCalls’s paper.

* Dr. Gene H. McCall is Laboratory Fellow (ret.), Los Alamos National Laboratory and a member of the ACD Board of Advisors.  He can be reached at

Categories: Communications, DHS, eLoran, FAA, GPS, Latest News, PNT, U.S., Wi-Fi

On The Campaign Trail

Check the dates and see when we're in your town!