The Navstar International Positioning System, generally often known as GPS, is acquainted to many smartphone customers because the expertise behind the blue location dot on map apps. However GPS, which is operated by the American house drive, was designed for the army. Since its launch in 1978 it has been joined by European, Russian and Chinese language equivalents, all utilizing the identical primary expertise: radio indicators from a constellation of satellites. A safer model of business GPS guides JDAM bombs, Excalibur precision-guided artillery rounds and GMLRS rockets, all utilized in giant numbers by Ukraine. However these weapons incessantly have their location techniques blocked by the Russians—generally fashions considered invulnerable have been affected. What are the army options to GPS?
Radio indicators from GPS satellites are weak, which means that an enemy can disrupt the system by drowning it out with competing radio noise. Army-grade variations use “M-code”, a army sign, and a few have directional antennas, angled upwards in direction of the supply of the sign, and noise filters to protect towards jamming. However Pentagon reviews leaked within the spring revealed that even some American weapons designed to forestall jamming have missed their targets in Ukraine.
Dana Goward, an adviser to the American authorities and president of the Resilient Navigation and Timing Basis, a non-profit, says generals have been warning Congress for years that the military is just too depending on GPS. Potential options and back-up techniques have been mooted, together with eLORAN, a radio navigation system that makes use of extra highly effective ground-based indicators, that are a lot tougher to jam however require much more transmitters. It could not, nonetheless, be suitable with GPS, and the proposal has been slowed down in dialogue.
Different options are already in use. The commonest is inertial navigation: Shahed-136s, Iranian-made loitering munitions procured by Russia, use it, and America’s military-grade GPS has it as a back-up system. Sensors within the weapon measure its acceleration and use this to calculate its velocity and path and therefore the place it’s in relation to its starting-point. Inertial navigation is efficient, however suffers from “drift”: small errors in measuring acceleration quickly produce bigger errors in location. Excessive-quality inertial-navigation techniques are extraordinarily costly.
Different approaches depend on seen landmarks. The Tomahawk cruise missile—an American munition designed earlier than the event of GPS—makes use of terrain-contour matching, or TERCOM, to search out its means, figuring out hills and valleys under it. For the ultimate method to a goal it compares the view from a video digital camera with satellite tv for pc pictures of the realm. No Tomahawks have been shipped to Ukraine. However some small drones can even navigate visually, utilizing a video feed all through their flight: they’ll establish landmarks and estimate their velocity and path from the motion of the bottom under them.
Such superior techniques are uncommon, however will in all probability turn out to be extra widespread as extra highly effective algorithms match onto smaller and cheaper chips. American-made Golden Eagle quadcopters first equipped to Ukraine have one of these GPS-free navigation as a part of their newest mannequin, and a few sources declare that Russian Lancet loitering munitions additionally use it. However the draw back of visible steering (at the very least for assaults) is that it depends on having a transparent view of the goal: it may be thwarted by smoke, mud, fog or different impediments.
Armies are working to enhance these options to GPS, for instance utilizing quantum sensors to make inertial navigation more practical, and growing new techniques, together with a navigation system primarily based on the Earth’s magnetic discipline. The simplest solution to substitute GPS will in all probability be a mixture of those applied sciences. For current weapons, growing new steering techniques and retrofitting them to current munitions will take years to do at scale. Within the meantime, the leaked Pentagon reviews on jamming in Ukraine suggest an easier answer: bomb the jammers.
© 2023, The Economist Newspaper Restricted. All rights reserved. From The Economist, printed beneath licence. The unique content material may be discovered on www.economist.com
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Up to date: 13 Sep 2023, 01:52 PM IST
