Auckland Weather 27/01/23 and Cyclone Gabrielle

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elpenguino

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#3083232 1-Jun-2023 11:18

neb:
neb: There was a very nearby strike at exactly 9pm that set off the motion sensors on the Timms traps, and shook the whole house in the process. They had been expecting thunderstorms, and the downpour was relatively brief.
Found out where it was, it took out a tree maybe 30m away. I'd seen half the tree lying on the ground but didn't realise it was lightning that brought it down. Edited to add: And here's the tree, or at least the lower half of it.

@neb

You've got a spot of ground truth data there.

What location for the event does your lightning system give and how much does it disagree with the tree's location?

Most of the posters in this thread are just like chimpanzees on MDMA, full of feelings of bonhomie, joy, and optimism. Fred99 8/4/21

neb

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#3083355 1-Jun-2023 15:32

It doesn't work like that, it's based on time-of-flight calculations from multiple stations, so you have a GPS-disciplined clock that timestamps E-field and H-field readings for sending to a central server, which then calculates strike locations if there are enough readings from other stations (there almost always are, you get ranges of 5000+ km so there are usually a few stations in range somewhere). However there's also a minimum range of 10-20km below which the signal overwhelms the front-end. A strike 30m away would have been caught up by protection circuitry and didn't even register in the readings.

elpenguino

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#3083359 1-Jun-2023 15:37

neb: It doesn't work like that, it's based on time-of-flight calculations from multiple stations, so you have a GPS-disciplined clock that timestamps E-field and H-field readings for sending to a central server, which then calculates strike locations if there are enough readings from other stations (there almost always are, you get ranges of 5000+ km so there are usually a few stations in range somewhere). However there's also a minimum range of 10-20km below which the signal overwhelms the front-end. A strike 30m away would have been caught up by protection circuitry and didn't even register in the readings.

So, you're saying the event was not detected by any sensors between 20 and 5000 km?

Most of the posters in this thread are just like chimpanzees on MDMA, full of feelings of bonhomie, joy, and optimism. Fred99 8/4/21

floydbloke

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#3083360 1-Jun-2023 15:40

neb: It doesn't work like that, it's based on time-of-flight calculations from multiple stations, so you have a GPS-disciplined clock that timestamps E-field and H-field readings for sending to a central server, which then calculates strike locations if there are enough readings from other stations (there almost always are, you get ranges of 5000+ km so there are usually a few stations in range somewhere). However there's also a minimum range of 10-20km below which the signal overwhelms the front-end. A strike 30m away would have been caught up by protection circuitry and didn't even register in the readings.

But would it charge the flux-capacitor??

Sometimes I use big words I don't always fully understand in an effort to make myself sound more photosynthesis.

neb

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#3083368 1-Jun-2023 16:07

elpenguino:
So, you're saying the event was not detected by any sensors between 20 and 5000 km?

It was reported by other sensors elsewhere that would have fed their readings to the site that processes and displays the data, but the graphical display on there only goes down to maybe a 20km grid so all you'd see is a white dot somewhere over the North Shore.

elpenguino

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#3083370 1-Jun-2023 16:17

neb:
elpenguino:

So, you're saying the event was not detected by any sensors between 20 and 5000 km?

It was reported by other sensors elsewhere that would have fed their readings to the site that processes and displays the data, but the graphical display on there only goes down to maybe a 20km grid so all you'd see is a white dot somewhere over the North Shore.

Right. Can you get the data in text form?

I see there's other sensors in the North Island which should a) be outside the range at which their front end would be saturated b) be close enough that their distance related errors will be less than sensors much further away.

Most of the posters in this thread are just like chimpanzees on MDMA, full of feelings of bonhomie, joy, and optimism. Fred99 8/4/21

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neb

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#3083376 1-Jun-2023 16:47

I don't think it's available, but even if it is it'd just be raw data, there's a huge amount of processing required to turn it into a strike position:

The network consists of more than 500 lightning receivers and some central processing servers. The sources of the signals we locate are in general lightning discharges. The abbreviation VLF (Very Low Frequency) refers to the frequency range of 3 to 30 kHz. The receiving stations approximately record one millisecond of each signal with a sampling rate of more than 500 kHz. With the help of GPS receivers, the arrival times of the signals are registered with microsecond precision and sent over the Internet to our central processing servers. Every data sentence contains the precise time of arrival of the received lightning discharge impulse ("sferic") and the exact geographic position of the receiver. With this information from several stations the exact positions of the discharges are computed.

If you really want the technical details (NB, you probably don't), this is the seminal work on sferics and thunderstorms.

elpenguino

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#3083378 1-Jun-2023 16:54

neb: I don't think it's available, but even if it is it'd just be raw data, there's a huge amount of processing required to turn it into a strike position:

I'm sure output data is available (otherwise what's the point? Just for the LOLs? ), but it sounds like you don't have access to it despite participating in the system.

Most of the posters in this thread are just like chimpanzees on MDMA, full of feelings of bonhomie, joy, and optimism. Fred99 8/4/21

neb

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#3083388 1-Jun-2023 17:44

Since it's just a raw data feed from hundreds of stations that's worthless without a huge amount of processing to turn it into something intelligible, even if it was available there's nothing I could do with it.

The processed data feed is freely available, see the link I posted earlier.

tdgeek

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#3083452 1-Jun-2023 18:37

I dont get the issue with lightning feeds, assuming thats what the last few posts are about?

neb

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#3083455 1-Jun-2023 18:40

tdgeek:
I dont get the issue with lightning feeds, assuming thats what the last few posts are about?

Nor do I, I was just responding to elpenguino's posts but was going to give up after the last one.

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