Analyzing a More Resilient National Positioning, Navigation, and Timing Capability

by Richard Mason, James Bonomo, Tim Conley, Ryan Consaul, David R. Frelinger, David A. Galvan, Dahlia Anne Goldfeld, Scott A. Grossman, Brian A. Jackson, Michael Kennedy, et al.

Research Questions

What are the technology-neutral requirements to back up and complement the positioning, navigation, and timing (PNT) capabilities of the Global Positioning System (GPS) for homeland security and critical infrastructure?

What are non-GPS sources for the PNT ecosystem?

Of these sources, what PNT capabilities are already implemented?

What are the threats to the functioning of the GPS satellite system and to other PNT parts of the national PNT ecosystem, both existing capabilities and potential backups or additions?

How do the costs of potential additions compare to the threats they would mitigate?

Because of the widespread use of the Global Positioning System (GPS) for positioning, navigation, and timing (PNT), concerns have been expressed that a disruption of GPS might require a national investment in backup capabilities. The authors assess the costs associated with realistic threats to domestic, nonmilitary uses of GPS, and review possible additions to the PNT ecosystem in light of those costs.

When the ability of individuals and organizations to adapt to and use existing alternatives and workarounds is taken into account, our analysis suggests that the costs of GPS disruption, while real, would not be as high as is sometimes assumed. When actual GPS jamming events have occurred in the past, users have felt the effects but generally managed to cope without disastrous consequences. Also, we consider it unlikely that any event short of nuclear war would deny all satellite navigation to the entire United States for more than a few days. At the same time, any system that could entirely replace GPS would be comparatively much more expensive than the damages it would mitigate.

Therefore, it is difficult to justify extensive investment in more GPS backups, although industry or government might well invest in PNT systems for their other merits, not just as a backup for GPS disruption per se. For example, the federal government is already investing in a system that will improve PNT for phone users in important urban areas, and this incidentally could also serve as a GPS backup.

Key Findings

The costs associated with Global Positioning System– (GPS-) focused threats were assessed
GPS is far from the only source of capability for positioning, navigation, and timing (PNT).

Many of these alternative and complementary PNT capabilities are already implemented broadly, and some additional technologies are being implemented for public safety or other purposes.

"Fallback" technologies—for example, navigation by traditional visual or manual course plotting, positioning using reference points—increase the robustness of PNT nationally.

The threat from spoofing GPS signals should not influence a decision about any new PNT systems, as robust means to counter spoofing already exist.

When cost estimates of GPS disruption or loss include realistic adaptation options and existing complementary technologies, the estimates are surprisingly low.

Additions to the PNT ecosystem in light of the potential benefits were considered

No single system is a perfect backup for GPS.

Given realistic cost estimates of GPS disruption, the bar for extensive government investment in a GPS backup (that does not serve some other purpose) is very high and therefore difficult to justify.

The federal government is already involved in one public-private partnership that will provide a GPS backup for many users in important urban areas.

Modest investments by the government in threat detection could also reinforce private incentives to maintain a robust PNT ecosystem.


Government investment in a "Global Positioning System (GPS) backup" appears unwarranted at this time. New positioning, navigation, and timing (PNT) systems could be developed for the complementary benefits they bring while GPS is operating, but not primarily as a backup for GPS outages.

Having diverse, time-proven, robust fallbacks to GPS available is highly desirable. Maintaining those capabilities while seeking the efficiency gains of modern PNT should be a priority.
Dispersal and diversity of capabilities in the national PNT ecosystem is a strength, not a weakness.

Considering both current and potential future systems, prudent system design necessitates avoiding dependencies that increase the risk associated with GPS loss.