Back-ups for GPS: Satellite-navigation systems at risk of jamming
20 years ago a similar venture in the UK and Australia attempted to create a dedicated network of towers for locating stolen vehicles. It didn&#x27;t survive. I think the beauty of GNSS at this point is that if you muck with it the whole population will notice, and that is kind of &quot;bad media&quot;. Not exactly winning &quot;hearts and minds&quot;.<p>While IIRC GLONASS, Beidu and Galileo have less than full-planet coverage, <a href="https:&#x2F;&#x2F;novatel.com&#x2F;support&#x2F;known-solutions&#x2F;gnss-frequencies-and-signals" rel="nofollow">https:&#x2F;&#x2F;novatel.com&#x2F;support&#x2F;known-solutions&#x2F;gnss-frequencies...</a> suggest there are a reasonable range of frequencies in use. As I am not a radio guy, in terms of countermeasures, then, would using multiple GNSS systems in places where their constellations are visible frustrate jamming, since standard ICs now support all systems?<p>In cars and boats, inertial navigation is also common. This is what provides the &quot;you are x% through the tunnel&quot; movement on car navigation screens. In the event that GNSS is lost, just like driving through a tunnel, one would expect operation to continue at a lower resolution &#x2F; slowly increasing error on many of these systems.<p>In addition, there are alternate systems for shipping. I believe AIS publishes last known GPS position&#x2F;heading, which RADAR and depth-sounding can confirm (along with terrain knowledge). By utilizing the shared state of nearby vessels prior to and during an outage, presumably inertial navigation assumption related error could be greatly reduced (as per the DGPS idea that IIRC was common prior to the unmasking of higher resolution GPS signals earlier in its public-use evolution).<p>Finally, free data sources for celestial navigation systems, terrain-based navigation systems (including bathymetry) and cell sites are available which can provide pretty reasonable estimates as well.<p>I think it&#x27;s a safe bet that, even more so than at present, future systems will typically operate on &quot;sensor-fusion&quot; to de-risk outages in sensitive applications.