3 ms·

This is patently false. Though we use Inertial, it's one component of an overall system that includes GPS. When we have degraded GPS we have to allow for large

This is patently false. Though we use Inertial, it's one component of an overall system that includes GPS. When we have degraded GPS we have to allow for larger error margins, based on time since last positional fix. There are other systems that allow us to reset the inertial, including manual fixes, if absolutely necessary. To say that a modern military doesn't use GPS for navigation is flat wrong.

jandrewrogers 5y ago
The US does not use GPS for primary navigation and never has. It is used for small corrections within the (classified) error bounds of INS, which is already very low in state-of-the-art systems. The US largely doesn't rely on a single INS either, but uses large networks of INS and other localization technologies to significantly reduce INS error. The purpose of GPS was to provide a highly accurate model of the world, not to navigate it per se. Some newer INS technology purportedly can reliably maintain precision within the error margin of GPS corrections for very long periods of time such that it renders GPS corrections largely pointless. The US considers this keystone technology for the military; the state-of-the-art is strictly controlled classified technology.
- jandrese 5y ago
  Last time I looked at INS the state of the art was laser gyroscopes. They were pretty good at maintaining your position, but still suffer from error buildup like any INS system. IIRC the drift became significant (more than 10m) over about a couple of hours of over-land driving. Very good by INS standards, but not something you can solely rely on.
  - livueta 5y ago
    I don't really know anything about this stuff, but recalled a quote from a reasonably trustworthy article I read recently that seems to support your position: https://www.economist.com/science-and-technology/2021/06/12/quantum-weirdness-helps-design-better-accelerometers https://www.economist.com/science-and-technology/2021/06/12/... > even the best military-grade inertial-navigation systems, which employ lasers, but not atomic interference, drift by kilometres a day. Though with this new fancy quantum stuff, INS-only might get more viable.
  - jandrewrogers 5y ago
    FWIW, state-of-the-art INS is not publicly available technology. No one knows what the real limits are, only that it is much less than what is available publicly. Cheap systems like guided bombs use conventional laser gyros but they don’t need to maintain their precision very long and they only accept GPS corrections within their drift error (a dozen meters?). When real precision is required, they tend to use laser guidance anyway.
- deleted 5y ago
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jandrewrogers 5y ago

The US does not use GPS for primary navigation and never has. It is used for small corrections within the (classified) error bounds of INS, which is already very low in state-of-the-art systems. The US largely doesn't rely on a single INS either, but uses large networks of INS and other localization technologies to significantly reduce INS error. The purpose of GPS was to provide a highly accurate model of the world, not to navigate it per se. Some newer INS technology purportedly can reliably maintain precision within the error margin of GPS corrections for very long periods of time such that it renders GPS corrections largely pointless. The US considers this keystone technology for the military; the state-of-the-art is strictly controlled classified technology.

jandrese 5y ago
Last time I looked at INS the state of the art was laser gyroscopes. They were pretty good at maintaining your position, but still suffer from error buildup like any INS system. IIRC the drift became significant (more than 10m) over about a couple of hours of over-land driving. Very good by INS standards, but not something you can solely rely on.
- livueta 5y ago
  I don't really know anything about this stuff, but recalled a quote from a reasonably trustworthy article I read recently that seems to support your position: https://www.economist.com/science-and-technology/2021/06/12/quantum-weirdness-helps-design-better-accelerometers https://www.economist.com/science-and-technology/2021/06/12/... > even the best military-grade inertial-navigation systems, which employ lasers, but not atomic interference, drift by kilometres a day. Though with this new fancy quantum stuff, INS-only might get more viable.
- jandrewrogers 5y ago
  FWIW, state-of-the-art INS is not publicly available technology. No one knows what the real limits are, only that it is much less than what is available publicly. Cheap systems like guided bombs use conventional laser gyros but they don’t need to maintain their precision very long and they only accept GPS corrections within their drift error (a dozen meters?). When real precision is required, they tend to use laser guidance anyway.
deleted 5y ago
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