(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).
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.
https://en.wikipedia.org/wiki/Triangulation
https://en.wikipedia.org/wiki/Trilateration
https://en.wikipedia.org/wiki/Multilateration
The More You Know.