Just before seeing this on HN, I randomly came across this article on "dark lightning" -- a burst of gamma rays that accompanies the RF burst that precedes visible lightning.
I believe this one also shows you an approximation of the thunder, so if you are close enough to a strike you can actually tell when you will hear the thunder. We were playing with it over the weekend and it was surprisingly accurate!
The Blitzortung paper mentions that sensor isn't accurate enough to use to determine the distance of a strike, so I don't think a crowdsourced phone-based network could work particularly well:
I also suspect that a phone's RF frontend would be awful for lightning detection as it is tuned for 900+Mhz signals. You can read more about lightning's RF properties here:
but it's clear that above 10Mhz you probably won't learn much of value about the lightning strike.
Elsewhere in this thread, an HN reader found that Nokia were working on lightning detection for phones, but it seems to use the FM radio receiver that was often built into SoCs, which could definitely tune itself to a much more useful frequency range.
Looks like Nokia had some plans (or at least patented something related) in 2007 [1]. According to ComputerWorld "The invention involves the use of radio frequency receivers in mobile phones, such as FM radio and GSM (Global System for Mobile Communications), to detect radio waves emitted by lightning."
Does lightning have any effect on the sensors that detect the geomagnetic field? Maybe even some small anomalies in the readings could be useful if many devices were working together.
It's huge. Normally, the curvature of the earth would make it impossible to detect anything at such distances. But the ionosphere's lower levels act like a waveguide [1], (and this tells you which frequencies you should listen on to take advantage of this).
The craziest phenomenon of this kind is whistlers [2]. Lightning strikes can be heard on radio at a point on the earth exactly symmetrical to the source, using the equator as plane of symmetry. In fact, the signal bounces around back and forth between the two points, following a line on the magnetosphere. The ones closer to the poles have longer paths, and their frequencies can get spread out over 3-4 seconds as they bounce around.
Cool stuff. I'm partial to the theory that prior mass extinctions have involved a meteor strike causing a whistler like effect on the opposite side of the plane causing volcanic action. eg https://en.wikipedia.org/wiki/Large_igneous_province#Meteori...
It seems to me that these strikes are happening in clusters at the same time 1000s of miles away. Is this related to radiation from the sun providing the tipping point?
Used this to find webcams of places with thunderstorms rolling in, and found this here in Switzerland [0], quite fun to watch when you skip through the history. Day started out lovely but now they are getting hammered.
I don't know how complete it claims to be (in terms of what fraction of lightning strikes in notionally covered areas it catches), but right now there's a storm very close to me (Cambridge, UK) and it's displaying a good fraction, but not all, of the strikes I see and hear.
(This is getting a bit pedantic but this is HN so we like to be accurate. And I learned the word on HN so might as well pass it on.)
Several of the other answers have mentioned "triangulation" but that's not quite right--that would imply that each listening station measures an angle towards the lightning source. But they don't--instead, they collect non-directional data consisting of arrival time stamps.
I believe the word for what they're doing is "trilateration".
Edit: I originally said "multilateration" but it turns out that's not quite right, either.
From your own source: "Multilateration is a navigation technique based on the measurement of the difference in distance to two stations at known locations that broadcast signals at known times....Multilateration should not be confused with trilateration, which uses distances or absolute measurements of time-of-flight from three or more sites"
I wonder if this could be used for a lightning based positioning system independent of GPS, if the events (time + position) were transmitted on longwave like the DCF77 time signal.
Wikipedia article on sound ranging provides a nice 2d picture and example on how this works (in the context of detecting enemy artillery using an array of microphones).
Electromagnetic (link is the "participants" tab on the top). You can tell because there's a smattering of telltale RF terms in the "comments" fields (coax, ferrites, E-field antenna, etc). I imagine that lightning strikes emit a fairly broad spectrum (localization in time -> delocalization in frequency) so the detectors might not all use the same band.
I would guess they have devices that detect light and sound. When the device detects a flash, it will start a timer and wait for the sound, which ends the timer.
Then based on the speed of sound, they can estimate the distance of the strike.
With many of these devices all over the place recording the data, using math, they can pinpoint the location of where the strike was.
No sound, as it does not travel far enough and is easily disrupted by any other sounds in the area of the detector.
I think it is just waiting for input of an electro-magnetical wave, then timestamps it and sends it to the server. The server can calculate the position with just the difference in arrival time to each station, and the position of those stations.
There is a project to detect lightnings over Moscow with cheap sound-only detectors on the roofs of skyscrapers, they managed to restore ever shapes of lightings in 3D with it:
So do the lines between stations and a strike mean that detector heard the strike? That's incredible if so... there's a station in California picking up strikes over Missouri.
From their FAQ, they pick up RF pulses, tag it with a GPS timestamp, and correlate on a central server.
"A lightning is a pulse not comparable to a broadcast signal on a single frequency. Such a pulse can be described best as a interference of several frequencies. Therefore a ferrite rod for lightning detection has to be a wide-band antenna."
Actually, the coverage in Europe is many many times better than the coverage in the US. The US actually gets that many more lightning strikes then Europe.
True, of course, but it's also worth remarking that there are huge spatial differences in lightning frequency due to the specific mechanisms causing thunderstorms.
I live in the U.S., and you rarely see t-storms on the Pacific coast here because the nearby Pacific Ocean is cool (due, in turn, to cool water brought down by the clockwise-turning North Pacific Gyre). But t-storms are very common in the Midwest and South due to the presence of warm, moist air there.
We get plenty of thunder here in the North East as well, even the occasional instance of thunder snow. Lightning is much more common in a majority of the US, excepting much of the lower west coast and southwest.
As mentioned by mnw, coverage is actually pretty sparse in North America (at least relative to Europe, presumably because it's a German project?). The continent simply has environments that are ideal for severe thunderstorms. I imagine the other continents are grossly underrepresented.
The funny part is that they happen mostly in the midwest and that area is sometimes called the 'bible belt' (for its strong evangelical christian population) and lightning strikes are a metaphorical means of punishment by God (as in "May lightning strike me down if I'm lying ...")
That irony aside, I am wondering about that South America number, it seems like at equidistant latitudes there are similar lightning environments on both sides of the equator and yet a nearly 16x reduction in number of strikes? What is up with that?
Your right of course. On the map the of lightning strikes they are (or at least were when I looked at it) happening in the Bible Belt according to the Wikipedia link. Along the top of Texas and up through Missouri. My error was in conflating the name of the regions.
I apologize to any folks who live in the region known as the midwest who were offended.
Where I live in West Central Florida we get about 50 strikes per square mile per year, 1.5 million per year for the state. Lightning is common here during the rainy season.
Cary resident here. In NC it's pretty much guaranteed that 90% of the days between mid-May and end-July will have a 30-40% chance of thunderstorms in the late afternoon to early evening. I like it, but it can make planning outdoor activities a bit tricky.
cool, I'm looking forward for this evening's thunderstorm to confirm if it's actually/acurately working :) Average delay appears to be between 3s and 10s here in Europe, but closer to 3s.
They show the detectors that picked up the strikes. I don't know if a single detector can determine distance, or if the strike location is triangulated using angles from multiple detectors.
[edit] Oh, the detectors are quite simple. They use GPS for position and time and report time-of-arrival of the elctromagnetic pulses. The server then uses that information to figure out where the strikes occurred.
This is absolutely amazing indeed! I wonder if the maps of blitzortnung (please change the name! To blitztracker or something.) match with data from commercial/public weather stations like metox:
http://www.sciencedaily.com/releases/2013/04/130424210319.ht...