[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).

[magicalhippo]

For a loitering drone I imagine dead reckoning would cause significant drift unless corrected by external input. GPS is great when it's available but can be jammed.

I was thinking along the lines of preprocessing satellite images to extract prominent features, then using modern image processing to try to match against the observed features.

A quite underconstrained problem in general, but if you have a decent idea of where you should be due to dead reckoning, then perhaps quite doable?

[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.