Indian Lightning Detection Network Launched

[Jonathan]

Hi All,

A new lightning detection network has launched, hosted by the  Centre for Lightning and Thunderstorm Studies (CeLTS), Department of Physics, Tripura University, India. The website can be found here.

The network utilizes six VLF receivers and vlfrx-tools, specifically the vttoga and vtspot utilities.

A minimum of five VLF receivers are required for accurate stroke solutions.

vttoga produces TOGAs (time of group arrival) from timestamped VLF spectrum data and can be configured to detect sferics based on band, amplitude, and scoring based on signal parameters of the sferic.

vtspot computes stroke solutions based on TOGA data from multiple receivers. Due to the model it uses, very distant strokes do not have the most accurate solutions, but in the case of this new network, it works quite well. 

On the website, you can click on the specific stroke and get various information. Here is an example:

StrokeID: 13015001 UT: 2022-06-21 11:17:27.475216 Lat/lon: 17.434,88.963

 site |        ut_timestamp        |   rms   |  te  | imprat | ascore |  dist  |  delay   |   vf   
------+----------------------------+---------+------+--------+--------+--------+----------+--------
 KK   | 2022-06-21 11:17:27.477204 | 0.04721 |  5.4 |   98.4 |   0.40 |  574.8 | 0.001988 | 0.9638
 T2   | 2022-06-21 11:17:27.477751 | 0.02712 |  1.1 |   71.2 |   0.67 |  743.1 | 0.002535 | 0.9771
 VW   | 2022-06-21 11:17:27.47827  | 0.01116 | -3.1 |   98.3 |   0.92 |  901.5 | 0.003054 | 0.9840
 DG   | 2022-06-21 11:17:27.479491 | 0.01633 | -1.9 |   25.2 |   0.89 | 1268.8 | 0.004275 | 0.9893
 TV   | 2022-06-21 11:17:27.480431 | 0.00742 |  1.4 |   78.9 |   0.81 | 1550.2 | 0.005215 | 0.9909
 AJ   | 2022-06-21 11:17:27.481203 | 0.02054 | -2.9 |   30.8 |   0.32 | 1783.0 | 0.005987 | 0.9927
(6 rows)

You can see the coordinates of the stroke as well as the TOGA, and various parameters of the receiver site's sferic, like RMS amplitude, velocity factor, timestamp, distance, delay, and ascore, a parameter that awards a score to a sferic according to how "sferic-like" it is. 

Using a network of VLF receivers and Whistler Catcher LEAF modules for the Tangerine SDR, I plan on creating a lightning location network just like this one. The good thing is, you don't need a Whistler Catcher as you can use a soundcard and PC/Raspberry Pi with GPS module right now. There is some setup and technical work involved and you have to be in a rural location, but it is possible to have a VLF receiver contributing to stroke solutions. Let me know if you'd like to contribute.

Jonathan

KC3EEY

[W8UM Ann Arbor]

I would like to learn the details.  Thanks, John

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[Jonathan]

Hi Willie,

Distant strokes originating from the opposite hemisphere won't give accurate solutions, but stroke solutions will be generated if it occurs within a polygon traced out by VLF receivers. It uses trilateration. See the vlfrx-tools documentation section of lightning location.

Hi John,

See vlfrx-tools documentation and a Raspberry Pi guide to setup vlfrx-tools on a Pi. 

Jonathan

KC3EEY

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[Dana Whitlow]

Are the relative timings of received stroke signals at various locations determined by

cross correlation, or merely by first threshold crossings of each, or by something else?

Dana   K8YUM

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[Jonathan]

Hi Dana,

They are determined by the sferic's time of group arrival, or TOGA. It's calculated by the utility vttoga. It accepts timestamped spectrum data from vlfrx-tools. For the TOGA to be accurate, it must be timestamped using GPS timing. 

Jonathan

KC3EEY

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[Richard Lamont]

Just thought I'd mention Blitzortung which is a worldwide amateur TDoA
lightning location network with hundreds of stations and which has been
in operation for several years.

https://www.blitzortung.org/

Richard G4DYA

On 21/06/2022 14:53, Jonathan wrote:
> Hi All,
>
> A new lightning detection network has launched, hosted by the Centre for
> Lightning and Thunderstorm Studies (CeLTS), Department of Physics, Tripura

> University, India. The website can be found here <https://ildn.in/imap.php>.

[Dana Whitlow]

I've been aware of Blitzortung and using it regularly for about 5 years so far.

Dana

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[Jonathan]

Richard,

Blitzortung has their own hardware and software is closed, plus it is only used for TOGAs. Using vlfrx-tools, which is open source, and much cheaper to build/buy VLF receivers, not only allows you to create a lightning location network, but a network of VLF receivers that can monitor SIDs, capture whistlers and chorus events, and make QSOs with VLF/ULF amateur transmissions below 9 kHz.

Dana, 

It almost feels like I've been on their hardware waitlist for 5 years!

Jonathan

KC3EEY

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[MNaruta GMail]

I have been Blitzortung station 1162 (USA, Michigan) since 2014.

Yes, they have been very stingy with new stations. I suspect
server data volume is the reason. Each station collects a lot
of data and preprocesses it to go on to the server(s). Even so,
it must tax the server(s). Perhaps a lesson to be learned?

The software is definitely closed. The CeLTS offers more.

I do find the Blitzortung USA web site (lightningmaps org) very
useful during Skywarn severe weather activities. A nice adjunct
to radar.

For personal use, I am still intrigued that I can know
beforehand when I will hear the thunder.


Michael - AA8K

[Jonathan]

Hi Michael,

Congrats on getting hardware too! I'm not really sure why they have
been reluctant with new hardware. I posted on their forum a while ago
providing TOGAs from vlfrx-tools, but they did not seem interested.

One of the challenges is discriminating sferics from others, and from
local interference. For example, local sferics often have little to no
skywave component and can sometimes look like interference. vttoga
uses a scoring system and can use a combination of different methods
for triggering and triggering parameters. Luckily, sferics tend to
have similar properties, and can be detected with a good deal of
accuracy. And I'm talking about cloud-to-ground strokes. Intracloud
strokes can be harder to discriminate.

I'm not sure how Blitzortung handles their data, but I'm sure the the
TOGA is computed on the hardware and sent along with some other
parameters. If the TOGA detector is using parameters that cause it to
trigger on false sferics, there would be quite a lot of false TOGAs
and the data would have to be pruned, but no one really knows for
sure. There are a lot of users, so that could be an issue too.

With vlfrx-tools, vttoga is highly configurable and you can set it to
detect most of the sferics based on it's triggering parameters. It
also can use multiple sferic bands as well. By default, it uses the 4
kHz - 17 kHz sferic band, but that could be split up and multiple
bands can be used.

And I agree, it is super cool and amazing to see the stroke before you
hear the thunder. I'd do the same thing by listing to my VLF receiver
or an AM radio.

Jonathan
KC3EEY

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[Gerald Creager]

This parallels the idea I presented at DCC several years ago. Hoping now, in retirement, and with the Grape SDR, I might pursue it. There are several reasons the BLitzortung system isn't ideal including closed source code and data. One of my original goals was to evolve a TDOA network and eventually a collaborative network for inter- and intracloud discharges worthy of being used, as the Citizen Weather stations are by the National Weather Service. Jonathon, let's talk some.

Maj Gerry Creager, CAP

National Health Services Advisory Group 

(C) 979.229.5301
Civil Air Patrol, U.S. Air Force Auxiliary
gocivilairpatrol.com

Southwest Region -- Civil Air Patrol  https://swrcap.com/

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[Jonathan]

Hi Gerry,

The utilities vttoga and vtspot of vlfrx-tools cannot differentiate between intracloud strokes and CG strokes, at least right now. It's difficult to do. I don't know if WWLLN or Blitzortung can differentiate either, but I haven't seen their raw data. 

My plan is to create something similar to ILDN using vlfrx-tools utilities vttoga and vtspot, utilizing volunteers to would install VLF receivers connected to the Whistler Catcher VLF module for the Tangerine SDR or a soundcard with Raspberry Pi/PC using vlfrx-tools as the processing pipeline, not only capturing whistlers, chorus, SIDs, etc, but TOGAs from multiple locations and performing geographic calculations of lightning strokes. Also, the hope would be that the volunteers provide triple axis reception (E-Field, N-S B-Field, E-W B-Field) so bearing and other extra data be captured. Currently, there is one E-Field VLF receiver installed.

Jonathan

KC3EEY

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[Gerald Creager]

Jonathan

One of the better ways to look for CC and IC is to look at VHF and UHF TDOA. There's a fair bit of existing science in there and I know a few of the experts, even if I retired from that shop. A couple are recently finished grad students... we might get them interested in HamSci, too. 

I need to play with vlfrx-tools. That said, Phil and I have gone back and forth and I don't think the RPi will have the bandwidth to do what I think will improve TDOA/TOGA: capture spectra that can be used to identify individual discharges. I've not followed the Tangerine development as well as I should but the short form is a USB channel from detector to the computer is underpowered. If Tangerine will directly interface to the VLF/LF port, perhaps via PCIe, would provide the bandwidth needed to look across a larger chunk of spectrum and hopefully the speed to digitize  at a higher sampling rate. There's a fair bit of analysis that remains to be done to determine sampling rates for lightning. When I discussed this with some of the NOAA and Univ. of Oklahoma lightning folks, they were honestly not thinking along the lines of spectral identification. What I'm hoping is that Vaisala isn't thinking along those lines, but if they are, I've documentation of prior art if they get snippy.

The geographic calculations will be trilateration. There's a world of literature on that process in the GNSS data, as that's how PNT positions are derived from all of the GNSS satellite systems. I'm not so sure triple axis data will prove useful but at this stage, it's better to have data we can eliminate than to try to crowbar it in later.

gerry

Maj Gerry Creager
National Health Services Advisory Team

Civil Air Patrol, U.S. Air Force Auxiliary

(M) 979.229.5301
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[Jonathan]

Hi Gerry,

If VHF and UHF TDOA, doesn’t that mean only local (to the antenna) intracloud strokes can be detected? The Tangerine currently has an HF receiver, but VHF and UHF might be something that could be developed in the future. 

Currently, I sample at 96 and 192 kHz using soundcards, particularly the AudioInjector Stereo and Pro for the Raspberry Pi. For timestamp alignment to GPS, the audio stream has to be resampled, and at 192 kHz, the Pi 3 gets fairly warm and draws more power, but a Pi 4 should handle that without much issue. For the Tangerine, that will have 384 kHz sampling and it will perform all of the signal acquisition “hard work” and output a vlfrx-tools-compatible stream. 

Are you looking for higher sampling rates for VHF/UHF? This receiver network I’m planning will only capture ULF/VLF spectrum up to 100 kHz. 

Triple axis reception, if properly calibrated, gives better confidence in stroke locations using vlfrx-tools. 

Jonathan

KC3EEY

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[Gerald Creager]

Depending on propagation, you may get "ghosts" with V/UHF detection but the characteristics of the discharge are notably different for CC/IC vs CG (regardless of CG polarity). I still need to get a handle on the best spectrum for CC/IC, which will be on my list after I get the shop and house renovation done. IF we were to establish a network of stations, CC/IC using V/UHF would need to be closer together. 

I am imagining a distributed processing matrix, with data collection further distributed. This would be similar to the Citizen Weather network architecture, save that all processing for CWOP occurs at a single site, but that site can be hot-swapped between Camp Springs MD and Boulder CO. Were we to have distributed parallel processing of TOGA/TDOA by trilateration and similarly parallel updates to a data or website, we'd be advancing the state of the art, especially if, unlike Blitzertung, the data were open-source with attribution (think Berkley-style). 

About 100-200 Khz has provided me with decent spectra. I've had to let this lay fallow for the last couple of years, but retirement offers a lot of potential to shake dust off research projects. Creating a dictionary of discharges is going to be high on my list to get started. It might be interesting to develop a network of ~10-20 stations to collect spectral data on discharges and analyze them for any unique characteristics, then create the aforementioned dictionary. In the processing phase, the receiving station(s) would do either an FFT or wavelet transformation which would be rapidly compared to the dictionary. They'd send a short packet with a station ID, TOA and dictionary tag to central processing which would then take on the (relatively) costly trilateration effort. I estimate each of the research stations would need to collect 10e06-10e08sample spectra for analysis. In some areas, that's a good summer... in others, 2-3 years of data collection.

gc

Maj Gerry Creager
National Health Services Advisory Team
Civil Air Patrol, U.S. Air Force Auxiliary
(M) 979.229.5301
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[Jonathan]

Hi Gerry,

In that case, would spectrum up to 100 kHz be of any interest then?
Any frequencies higher than that the Pi would not handle well, at
least not in real time.

For 100-200 kHz, the Tangerine SDR's RF module can handle as its lower
limit is 100 kHz, however, there currently isn't any software in place
for the application of stroke analysis and location for the RF module.
Using other SDRs, one can develop the software for that band as well
as VHF/UHF.

What I'm working on is spectrum data up to 100 kHz with an emphasis of
up to 20 kHz. Would that be useful to you?

Jonathan
KC3EEY

> Maj Gerry CreagerNational Health Services Advisory TeamCivil Air

> Patrol, U.S. Air Force Auxiliary
>
> (M) 979.229.5301
>

> GoCivilAirPatrol.com <https://www.gocivilairpatrol.com/>
> <https://www.gocivilairpatrol.com/>

>> Maj Gerry CreagerNational Health Services Advisory TeamCivil Air Patrol,

>> U.S. Air Force Auxiliary
>>
>> (M) 979.229.5301
>>

>> GoCivilAirPatrol.com <https://www.gocivilairpatrol.com/>
>> <https://www.gocivilairpatrol.com/>

>>>> *Maj Gerry Creager, CAP*

>>>> National Health Services Advisory Group
>>>>
>>>> (C) 979.229.5301
>>>> Civil Air Patrol, U.S. Air Force Auxiliary

>>>> gocivilairpatrol.com <http://www.gocivilairpatrol.com/>

>>>> https://groups.google.com/d/msgid/hamsci/CAG3zga4wJogcS6CNG6WMW9aM_1qhpvFLKd9%3D5wL1GB2e%3DzKOhA%40mail.gmail.com
>>>> <https://groups.google.com/d/msgid/hamsci/CAG3zga4wJogcS6CNG6WMW9aM_1qhpvFLKd9%3D5wL1GB2e%3DzKOhA%40mail.gmail.com?utm_medium=email&utm_source=footer>
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[Gerald Creager]

I think it would be useful, Jonathan. I really want a good lab-grade SDR to oversample the spectrum both in terms of bandwidth and sample rate... Talking to my former colleagues at NSSL, they'd not explicitly done that, so it'd be novel. the 20-100 kHz space is also of particular interest. One researcher at OU, now long departed, was interested in the spectral signature up to several MHz, as he felt there was data in the higher frequencies. 

Historically, "everyone" has decided the low frequency spectrum has all the information we need. For TDOA/TOGA, probably true, for the most part, but the idea of spectral signature matching and central processing would be more powerful than trying to have each station perform the work itself. Centralized processing is consistent with NLDN, Blitzortung and several other networks. I can envision a couple of network and central processing architectures that'd be innovative, though.

Headed back to work. I'm playing renovation electrician today, trying to identify the circuits I'm working on so they won't kill me. With luck, 20-30 outlets will be finally wired today...

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