
Darpa Seeks Tools to Capture Underground Worlds in 3D - zeristor
https://www.darpa.mil/news-events/2019-03-07
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inflatableDodo
ADR scanning. - [https://adrokgroup.com/](https://adrokgroup.com/)

also available in small -
[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2008164/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2008164/)

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contingencies
[https://en.wikipedia.org/wiki/Borescope](https://en.wikipedia.org/wiki/Borescope)

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zeristor
This is the more enticing website:

[https://www.subtchallenge.com/](https://www.subtchallenge.com/)

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zeristor
How far are built in phone gyroscopes from providing inertial tracking for
underground, it would be handy to walk around Tube stations and see how
there're all connected, but the accuracy seems to be someway off.

Although this looks to be a lead:

[https://aaltovision.github.io/handheld-
INS/assets/presentati...](https://aaltovision.github.io/handheld-
INS/assets/presentation.pdf)

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mparr4
Pure inertial navigation gets worse over time, even a $20,000 gyroscope
wouldn't get the job done.

This is because gyroscopes measure rotational velocity, velocity is the first
derivative of position, so you need to integrate velocity in order to get
rotational position. The integral of velocity is (velocity x time), so your
error gets bigger over time.

I'd imagine an inertial solution plus optical flow could result in some pretty
good results.

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donquichotte
I was always under the impression that integrating unknown biases in gyroscope
and accelerometer measurments is the main issue with dead reckoning.

Today I am convinced that attitude errors are the far bigger issue, since they
will make you misinterpret gravity as genuine acceleration.

Even with a 1° error in your pitch estimate, you will start integrating
9.81ms^-2*cos(1°) = 0.17ms^-2 as a forward acceleration. Within one minute,
you are 308m off already. This is the real issue with dead reckoning IMO.

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salty_biscuits
It's complicated. It depends on the sensor and the motion of the object.
Because the gravity vector doesn't change spatially very quickly if you are
doing loops you can use the accelerometers to calibrate the gyro biases in the
sensor fusion loop (via the gravity vector). You can also use the magnitude of
the vector to calibrate the accelerometers (roughly). Nothing helps pin all
that stuff down like a global position measurement though. Some sensors are
just less prone to bias drift as well.

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pedalpete
This is exactly what emesent do [https://emesent.io/](https://emesent.io/)

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salty_biscuits
Yeah, they are a spin off of a CSIRO project. Good to see that sort of thing
coming out of Brisbane.

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pontifier
I thought this was the goal of project tango.

I had one of the tablets, and even started to explore the idea of mapping
caves with it for a while.

The combination of an accurate IMU and the depth sensor made it perfect for
mapping this type of environment.

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dmix
You can see some of the initial teams competing here:

[https://www.darpa.mil/news-events/2019-01-22](https://www.darpa.mil/news-
events/2019-01-22)

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zeristor
Wasn’t there talk of applying the new wave of quantum sensors for this?

There’s gravimetric ones that can detect underground cavities

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zeristor
So is this comparable to DARPA’s driverless car challenge from several years
ago?

