The Navstar Global Positioning System, widely recognized as GPS, has become a household term for smartphone users due to its role in powering the familiar blue location dot in map applications. Originally designed for military purposes, GPS is currently managed by the American space force. Since its inception in 1978, other nations, including Europe, Russia, and China, have launched their own satellite-based navigation systems using similar radio signal technology. A more secure version of GPS is employed in guiding military ordnance such as JDAM bombs, Excalibur precision-guided artillery rounds, and GMLRS rockets, which are frequently utilized by Ukraine. However, Russian interference often disrupts the location systems of these weapons, even affecting models previously considered impervious. So, what are the military alternatives to GPS?
GPS satellite signals are susceptible to interference due to their weak radio signals, which can be overwhelmed by competing radio noise from adversaries. Military-grade versions utilize “M-code,” a military signal, and some incorporate directional antennas that point towards the signal source, along with noise filters to defend against jamming attempts. Nevertheless, leaked Pentagon reports in the spring disclosed that even certain American weapons designed to counter jamming failed in Ukraine.
Dana Goward, an advisor to the American government and president of the Resilient Navigation and Timing Foundation, a non-profit organization, has long cautioned Congress that the military relies excessively on GPS. Various alternatives and backup systems have been proposed, including eLORAN, a ground-based radio navigation system employing more potent signals that are challenging to jam but require a significantly larger number of transmitters. Nonetheless, eLORAN would not be compatible with GPS, and discussions surrounding its implementation have been slow-moving.
Some alternative navigation methods are already in active use. The most prevalent is inertial navigation, which relies on sensors within the weapon to measure acceleration and calculate its speed and direction relative to its starting point. Inertial navigation is effective but is susceptible to “drift,” wherein minor errors in acceleration measurement quickly lead to substantial location errors. High-quality inertial navigation systems are also quite costly.
Other approaches depend on visible landmarks. The Tomahawk cruise missile, designed prior to GPS, employs terrain-contour matching (TERCOM) to navigate by identifying topographical features such as hills and valleys. During the final approach to the target, it compares the real-time video feed with satellite images of the area. While no Tomahawks have been delivered to Ukraine, some small drones can perform visual navigation by identifying landmarks and estimating their speed and direction based on ground movement. These advanced systems, though relatively rare, are expected to become more prevalent as more powerful algorithms are integrated into smaller and more affordable hardware. American-made Golden Eagle quadcopters supplied to Ukraine already incorporate GPS-free navigation in their latest models, and there are claims that Russian Lancet loitering munitions also utilize similar technology. However, visual guidance is limited by the need for an unobstructed view of the target and can be impeded by smoke, dust, fog, or other obstacles.
Efforts are underway to enhance these GPS alternatives, including the utilization of quantum sensors to improve inertial navigation accuracy and the development of new systems based on Earth’s magnetic field. The most likely path to replace GPS will likely involve a combination of these technologies. Retrofitting existing munitions with new guidance systems and scaling up their production will take several years. In the interim, the leaked Pentagon reports on jamming in Ukraine suggest a more straightforward approach: targeting and neutralizing the jamming equipment.
Source: with agencies