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| Riding Earth’s Magnetism: An Alternative Approach to PNT | | NSPS | | Threats to the Global Navigation Satellite System from spoofing and jamming and the possibility that GNSS satellites could be destroyed accidentally by space debris or intentionally during a war has led to a search for alternative sources of positioning, navigation and timing (PNT) data. Potential alternative PNT (APNT) approaches include computer vision, terrain contour matching (TERCOM, which was used to guide cruise missiles in the 1970s and 1980s), and using magnetic anomalies (MAGNAV). Earth’s crustal magnetic field varies from location to location as much as topographic features do and, like them, it changes very little over time. However, unlike topographic features, which only occur on the third of the planet’s surface covered by land, magnetic variations also occur on the oceans. This makes them potentially very useful as landmarks to the Navy and Air Force. Magnetic variations have the additional benefit that they cannot be jammed or spoofed. Just like other features of Earth, magnetic fields can be mapped, using scalar magnetometer sensors to measure their strength and direction. In fact, government agencies and mining companies have been making these maps for many decades, for geological exploration and other purposes, though mostly on land. |
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