North Korean ICBM launch detected using GPS

“Geospatial Information Authority of Japan (GSI) operates GNSS CORSs that cover Japanese archipelago with over 1,300 stations at an average interval of about 20km for crustal deformation monitoring and GNSS surveys in Japan.” [2]

Basically the government of Japan pepered their country with GPS base stations and they let researchers use the data from them. This is just a novel use of that data.

1: https://mobile.twitter.com/tylerni7/status/15934664867144212...

2: https://www.gsi.go.jp/ENGLISH/geonet_english.html

For made up simplified example, assume you have a moving GPS in an airplane or something, and there's exactly four sats N S W E. All four sats relatively agree you're flying the plane normally in a straight ish line as usual. Suddenly, the data from the S sat gets wildly distorted, but the other three sats remain normal. I suppose the S sat could have malfunctioned but more likely something is in between your plane and the S sat. So your navigation chip tosses the data from the S sat and marks its SNR way down and generally ignores that sat... However, if you were to log that "bad" data from the sat to the south... then compare to someone flying a plane a hundred miles to your south, and their GPS reports data suddenly was trash to their north, then you know something flew between your two planes. Maybe an ICBM, maybe a thunderstorm, maybe a GPS jammer weapon, a lot of "it depends". Sometimes its the data thats tossed out thats the most interesting.

I've been fooling around with something a LOT cruder at home WRT tracking thunderstorms. Its not rocket surgery to know that severe rain attenuation can impair GPS signals. One of the standard NMEA output lines contains each sats SNR, so if I know from my "vast" database that in normal weather satellite #43 at az 45 degrees elevation 45 degrees reports a SNR of made up number -10 plus or minus 2 over the past few years, then if it reports -20 today that would imply either the sat just burned out (unlikely) or there's a rain cloud causing "about 10 dB attenuation" at az 45 degrees elevation 45 degrees relative to my house. The linked project in the article is enormously fancier of course than merely logging SNR fluctuations.

I'm amused at the idea of crowdsourcing a "large amount" of forest hiking data over time to evaluate the health of the tree canopy in forests. Where I live the leaves are all down now so GPS signals should be very strong for hikers in forests.

As the Air Force discovered decades ago, for various EE and trigonometry reasons, bistatic radar works best overhead its kind of the opposite of what you want for an early warning radar so you can see why bistatic radar never went much of anywhere compared to traditional radar for the usual Air Force mission purposes. Although there are interesting modern "IoT" distributed sensor applications, at least if you have unimpeded fast communications systems, etc.

This is false. Putin is not afraid of shining a very bright radar into the sky to know when missiles are about to hit them. That is the standard and reliable way to go about this.

Have you heard about the “woodpecker” signal? It was the transmission of a giant over-the-horizon early warning radar system. It is now defunct, has been replaced by more modern systems, but when it was operational you could receive it basically anywhere on Earth. That is the scale sovereigns play on.

Only people who don’t have the backing of a sovereign state need to go about detecting launches in this circumspect method.

> Some domain specific knowledge was meant to be esoteric

Yes. But this is not that.

> there are a variety of better licenses such as CC-non-commercial that allow peaceful uses of the code without allowing it to be used by literally anyone on the planet

Are you kidding me? :) In the top of your comment you worry, wrongly, about Kim and Putin using the given code. And your suggested solution is to release it under a different licence? :) You think they would care about that?

I don't have a fully formed opinion on the rest of your comment, however I can definitely point out that software licensing on open source software will not stop a nefarious third party from using it. They're nefarious!

To a practical point though, information asymmetry is powerful in war, but the cat was already out of the bag for this technology as it's in public papers. The code is just an application of information that was already public, they could probably write their own version of the same code based on the papers.