Weaknesses in the Global Positioning System were already a concern for the Department of Transportation and Defense Department, but an increased risk of cyberattack has raised concerns about the safety of GPS satellites.
DOT published its initial report outlining the implications of system failure in 2001, and last year released a report that highlighted 11 possible technologies that could provide GPS backup. Concerns about spoofing and hacking have also led the DOD to seek out -backups and alternatives to the essential system.
“GPS is really vulnerable,” says Dana Goward, president of the Resilient Navigation and Timing Foundation. “The signal strength is incredibly weak, and because we wanted everybody to adopt it, we made the codes public. So, anybody can build a transmitter that can imitate a GPS satellite.”
To address the weaknesses in the GPS, several possible backups are in development.
The U.S. Air Force is testing a magnetic anomaly navigation technique that uses the earth’s magnetic field and sensors that measure patterns in geology, forming maps that can be used to determine position and navigation. The “mag in a box” has been used on the F-16 and other military assets; in 2021, a team at Wright-Patterson Air Force Base attached a sensor to the wing of a C-17 Globemaster III and tested different locations for the magnetometer to capture information.
Enhanced Geolocation Architecture Is Under Consideration
Long-range navigation (LORAN) was first used during World War II, and an enhanced version, eLORAN — one of the technologies mentioned in the DOT report — has been proposed as a terrestrial alternative to GPS. According to DOT, eLORAN signals are up to 3 million times stronger than GPS, and authentication broadcasts are secure and resist spoofing.
Goward calls eLORAN a “leading candidate” for a GPS backup, noting that countries including Russia, China, Saudi Arabia and South Korea operate a version of eLORAN for terrestrial navigation.
Rather than develop an alternative to space-based GPS navigation, the Space Force program is developing new architecture known as GPS Enterprise, which includes space, control and user equipment to create unjammable GPS access. The DOT approved the plan in 2018, and it’s expected to come online in late 2025.
Another possibility: adding chip-scale atomic clocks in DOD vehicles or precision-based munitions to allow navigation in GPS-denied environments. The technology is commercially available, according to John P. Skudlarek, position, navigation and timing (PNT) team lead for the Office of the DOD Chief Information Officer. “Chip-scale atomic clocks, initially developed for military use, also have civilian applications,” he adds.
Skudlarek believes it will take time to ensure that GPS alternatives are resilient and survivable — and there might not be a single option for replacement. “Maturing technologies from basic research through prototyping and into full development is a complex process that requires trial and error,” he says.