[fnordpiglet]

Occurred to me that in a war or over the water this wouldn’t be useful. But I think it will be a useful technology (that to be fair likely already exists), in addition to highly accurate dead reckoning systems, when GPS is knocked out or unreliable, as secondary fall back navigation.

[krisoft]

> in a war … wouldn’t be useful

Why do you say that? Navigational techniques like this (developed and validated over longer timeframes of course) are precisely for war where you want to cause mayhem for your enemies who want to prevent you from doing that by jamming GPS.

This is not just an idea but we have already fielded systems.

> over the water this wouldn’t be useful

What is typically done with cruise missiles launched from sea that there is a wide sweep of the coast mapped where it is predicted to make landfall. How wide this zone has to be depends on the performance of the innertial guidance and the quality of the fix it is starting out with.

[hef19898]

Well, landmarks have a tendency to change quickly in a war zone. Making whatever map material you have useless, or close to useless.

All the navigational methods predating GPS still work perfectly fine so.

[heisenbit]

For the human eye maybe. For a computer using statistics less so. Extracting signals under a mountain of noise is a long solved problem - all our modern communication is based on it.

[littlestymaar]

You can get new satellite imagery ever day… (be it military ones if you're a major power, or just commercial one like your average OSINter)

[hef19898]

Sure. And then you have to upload those new, and vetted, imagines to all your drones. Other nav data is much more stable.

Mind you, military hardware is not your smartphone, OTA updates are usually not a thong for various reasons.

The approach for sure is interesting so.

[krisoft]

That is all really interesting speculation, but I'm not describing a system which could be, but one which is already available and fielded. In cruise missiles it is called DSMAC.

Here are some papers: https://secwww.jhuapl.edu/techdigest/Content/techdigest/pdf/...

https://apps.dtic.mil/sti/tr/pdf/ADA315439.pdf

[hef19898]

Basically inertia guidance enhanced by terrain matching. Which is great, but terrain matching as a stand-alonenis pretty useless. And it still requires good map data. Fine for a cruise missile launched from a base or ship. Becomes an operational issue for cheap throw-away drones launched from the middle of nowhere.

[Zetobal]

Yes, that's also how it works right fucking now.

[magicalhippo]

Well if you combine it with dead reckoning, I guess even a war torn field could be referenced against a pre-war image?

I mean, a prominent tree along a stone wall might be sufficient to be fairly sure, if you at least got some idea of the area you're in via dead reckoning.

[hef19898]

And deadrecking is already standard in anything military anyways. For decades.

As an added data source to improve navigation accuracy, the approach sure is interesting (I am no expert in nav systems, just remotely familiar with some of them). Unless the approach was tried in real world scenarios, and developed to proper standards, we won't see it used in a milotary context so. Or civilian aerospace.

Especially since GPS is dirt cheap and works for most drone applications just fine (GPS, Galileo, Glanos doesn't matter).

[KaiserPro]

You can't use visual key-points to navigate over open water.

You can use other things like Visual Odometer, but there are better sensors/techniques for that.

What it can do, if you have a big enough database onboard, and descriptors that are trained on the right thing, is give you a location when you hit land.

[Tostino]

That's exactly what the comment you replied to was describing.

[TeMPOraL]

> You can't use visual key-points to navigate over open water.

No, but you can use the stars. Even during the day.

[KaiserPro]

true, but that requires an accurate clock, and specialised hardware. Ideally you also need to be above the clouds as well.

[jnwatson]

For only $300 plus shipping from Ali Express you get a high accuracy inertial navigation system. Only weighs 10 grams.

The future is scary. It is now straightforward and inexpensive for lots of folks to construct jam-resistant Shahed-style drones. https://www.aliexpress.com/item/1005006499367697.html

[Animats]

And for a little less, you can buy the original, from Analog Devices.[1]

Those things are getting really good. The drift specs keep getting better - a few degrees per hour now. The last time I used that kind of thing it was many degrees per minute.

Linear motion is still a problem, because, if all you have is accelerometers, position and velocity error accumulates rapidly. A drone with a downward looking camera can get a vector from simple optical flow and use that to correct the IMU. Won't work very well over water, though.

[1] https://www.analog.com/en/products/ADIS16460.html

[sigmoid10]

>Linear motion is still a problem, because, if all you have is accelerometers, position and velocity error accumulates rapidly.

An INS will usually need some kind of sensor fusion to become accurate anyways. Like how certain intercontinental ballistic missiles use stars (sometimes only a single one) as reference. But all these things are based on the assumption of clear sight and even this google maps image based navigation will fail if the weather is bad.

[Animats]

10^-5 degrees/hour drift was achieved in the 1970s, for ICBMs, at very high cost.

[pjc50]

The laser ring gyro? It'll be fun when those start showing up on Aliexpress.

[deno]

Sold by "Peace Dove Grocery Store."

[ufocia]

Sounds expensive.

[dilyevsky]

“High accuracy”

[Modified3019]

For oceans, they could use juvenile loggerhead turtles: https://www.reed.edu/biology/courses/BIO342/2011_syllabus/20...

[mytailorisrich]

Being able to nagivate using only a map stored locally sounds extremely useful in a war.

[dwighttk]

Don’t we have basically this but it looks at stars?