The now habitual jamming of GPS signals is prompting a push toward advanced alternatives that cast doubt on the long-held assumption that the future of terrestrial navigation lies solely with orbiting GPS satellites. An effective solution promises to become a major market opportunity.

The search for GPS alternatives is being prompted by the harsh reality of the modern battlefield where GPS signals can be jammed, spoofed or knocked out completely, potentially disrupting navigation for modern weapons systems.

The range of alternative navigation tech under consideration is extraordinary. Honeywell recently turned heads with a test flight of an Embraer 170 passenger plane that flew from Puget Sound near Seattle to southern Alaska and back. The four-hour, 23-minute flight relied on a quantum-based navigation aid called MagNav that used weak changes in the Earth’s magnetic field to determine the plane’s position with 89 percent greater accuracy than traditional backup navigation methods. The test flight was part of the Pentagon’s MagNav program.

A GPS alternative may not be a one-tech-fits-all solution. For example, the U.S. Navy this month tested a GPS-denied landing of a drone on a moving ship using a system of commercially available cameras, sensors and software that allowed the drone to recognize the ship. The remarkable aspect of the test was the development of algorithms that predicted deck movement in real time to support a controlled landing. Traditional shipboard drone recovery relies on expensive radar systems, specialized deck equipment and ship modifications. The U.S. Navy intends to scale up this less costly approach to drone navigation to larger aircraft, with potential applications for the Collaborative Combat Aircraft (CCA) program, designed to develop robotic wingmen for manned fighters.

The UK, meanwhile, is investigating another GPS-denied naval navigation aid for sea drones. Developed by Voyant, the system uses software to compare radar images to preloaded reference maps to estimate the drone’s position relative to surrounding terrain and coastal features, an approach the company says is particularly useful in often cluttered littoral waters.

GPS-denied solutions may include using “signals of opportunity” from other types of satellites and ground-based sources. General Dynamics early this month demonstrated a software-defined receiver called MO-Nav aboard a reusable Talon-A hypersonic test aircraft capable of speeds of Mach 5 or higher. The receiver analyzes radio-frequency signals from satellites and commercial ground sources to determine its position.

“GPS-denied technology is arguably one of the largest capability gaps across joint forces,” said Matt Elliott, a General Dynamics Mission Systems director. The software-defined receiver allows “programs to continuously outpace the threat with software upgrades instead of requiring new hardware insertions.”

In a similar vein, a Spanish drone maker called UAV Navigation is working with the European Space Agency (ESA) to use signals from low Earth orbit (LEO) satellites normally used for internet access that would be combined with inertial measurements, air data and potentially vision-based navigation.

The cutting edge of GPS-denied navigation is projects like the chip-scale gyroscope being developed by researchers at Caltech and the University of California, Santa Barbara. The new gyroscope can detect rotation as slow as 37 degrees per hour, making it nearly 2,000 times more sensitive than an earlier silicon nitride design. The new chip detects the movement of light traveling through a ring-shaped optical circuit. The new device offers the potential for high-precision navigation in a smaller, more durable package. The goal is a chip-based gyroscope that would measure a rotation rate of 15 degrees per hour. That’s the rotation speed of the Earth itself.