
Darpa to re-invent GPS navigation without the use of satellites - DiabloD3
http://www.extremetech.com/extreme/202111-darpa-to-re-invent-gps-navigation-without-satellites
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bitwize
Inertial and GPS-based navigation systems have always been complementary
components of a complete navigation solution. The problem with inertial
navigation is, it because you are reckoning position by taking the second
integral of acceleration, error is introduced and what's worse, it
accumulates. No matter how accurate the gyros and accelerometers, if you run
the system long enough the drift accumulated will have you off from your
actual position. So GPS is used to correct the inertial solution with actual
position data.

So yeah, it's great that we're getting much better solutions from inertial
gear to supplement a faulty or missing GPS solution. But this isn't GPS
without satellites.

Now... navigation on or over land by performing SLAM on ground features...
that would be interesting.

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toomuchtodo
> Now... navigation on or over land by performing SLAM on ground features...
> that would be interesting.

I'd more be interested in guidance using x-ray emissions from pulsars and
neutron stars. Constant reference points that are almost impossible to jam.

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bronson
True, but you could just use stars. The SR-71's celestial navigation unit
could get a fix during the day while it's sitting on the ground:
[https://books.google.com/books?id=xwPFC3GtcL8C&pg=PA132&lpg=...](https://books.google.com/books?id=xwPFC3GtcL8C&pg=PA132&lpg=PA132&dq=Nortronics+NAS-14V2&source=bl&ots=gjLGqSECed&sig=etODqzN_hNYyNRwhSXpQRbvovmg&hl=en&sa=X&ei=ZMQYVaDpIojroASzxIJg&ved=0CEoQ6AEwCTgK#v=onepage&q=Nortronics%20NAS-14V2&f=false)

The Nortronics NAS-14V2 was designed in the early 60s. I would _love_ to see
the insides of one of those things.

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abcd_f
Clouds, fog and smoke are the obvious issues. Dense tree canopies too.

~~~
zo1
Sure, those are all obstacles. But the way I see it, they can all complement
each other. I.e. One of the posters mentioned drift of accuracy for some
alternate positioning methods. You could then periodically, when possible, use
this more-accurate but obstacle-susceptible system to "correct" the drift.

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ethanbond
I'm sure there's a lot of novel stuff they're trying to do here, but the
article seems to seriously skirt that inertial navigation systems are all
around us and in fact predate GPS by _a lot_.

Doesn't seem to me they're re-inventing GPS, just making better INS.

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KaiserPro
yeah, that was the impression that I got to. Shame the article was 80% waffle.

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jsprogrammer
Halfway through the 7th paragraph (of 8) and finally a vague answer to what
the title promised.

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femto
Geographic location could fall out as a side-effect of increased use of
passive radar. Whilst it hasn't happened yet, the UK is testing whether it can
use passive radar for air-traffic control [1]. If a radar receiver can figure
out the position of a target, it would be even easier (no losses due to
reflection) for the target to receive the same signals and figure out its own
position. With a wide-band receiver, using all available incidental sources,
it would also be hard to jam, since an adversary would have to have control
over the entire electromagnetic environment. It would be even harder to jam if
the receiver was using a phased array to figure out directions to sources,
allowing it to null interference.

[1] [http://www.atc-network.com/atc-news/airbus-defence-and-
space...](http://www.atc-network.com/atc-news/airbus-defence-and-space-
awarded-caa-study-for-passive-radar-use)

~~~
Johnythree
Sounds a lot like "VHF omnidirectional range" (VOR) which dates back to 1946.

[http://en.wikipedia.org/wiki/VHF_omnidirectional_range](http://en.wikipedia.org/wiki/VHF_omnidirectional_range)

~~~
femto
In so far as VOR is the locational analogue of traditional "rotating beam"
radar, but there the similarity stops. VOR has a known structure to its
intended transmissions. Passive radar relies on incidental transmissions, and
the system learns about any structure in the received transmissions. Passive
radar has potential for much greater accuracy (better than GPS??), as it can
potentially use a huge bandwidth.

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tajen
The interesting section:

> including novel inertial measurement devices that use cold-atom
> interferometry; chip-scale self-calibrating gyroscopes, accelerometers and
> clocks; and pulsed-laser-enabled atomic clocks and microwave sources

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zimbatm
Would it be possible to depend on the earth's magnetic field for positioning ?
Migratory birds use it but I don't know how precise it is.

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icegreentea
So called 9 axis inertia guidance units exist (3 linear accelerometers, 3 axis
gyroscope, and 3 axis magnetometer). The magnetometers are particularly useful
for dealing with gyroscope drift. Once you reject stuff like mains hum, in
most typical situations, human scale magnetic fields tend to be pretty
constant for many timescales in most human situations.

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userbinator
Could they be inclined to, sometime in the _very far_ future, shut down GPS
completely? Many other countries have realised that GPS is entirely US-owned,
and launched their own GNSS services already.

