Lightning Catcher

Yes, winter - not the best time for an article on the zipper. But the time is coming! The rainy season and thunderstorms likely after some 4-5 months and work - more than enough.

Everyone saw the lightning? Zips beautiful, twisted. You know how they really look like? Yes, they manage photograph, but with only one hand, and through time.

And we have learned to catch every lightning, and even build a full 3d model of each, even the invisible zipper in the clouds! Moreover, after 15 seconds after the impact at any point over Moscow, and its three-dimensional coordinates of the profile is immediately updated on our website!
Under the cut 6 MB traffic.

What is lightning? As it emerges? Wikipedia gives the most complete and detailed response, but a brief squeeze the essence of lightning, an important day following description from there so:

• Lightning accompanied Flash and thunder Lightning must be at least a few hundred meters and have an average length 2.5 km Lightning are land (which beat into the ground, very rare) and vnutreoblachnye
• In the cloud, there is «Impact ionization» , which is the beginning of lightning and appears «Leader-charge» , which will continue to wade through the atmosphere, paving the way for the main the charge.
• Leader spontaneously chooses a point in space, located a few meters away, and with great speed flies there, thus creating «channel» , and emits low "hryas »
• The leader of the movement and makes stops at the point at which flew there and waiting for a few microseconds. During this time, the base of the cloud at all before that creates channels silently passes a small discharge, feeding the leader.

Then again he performs steps 2-3 until it reaches either the ground (which is extremely rare), or other accumulations charge in another cloud, where it dissipates its charge. Once the leader has reached the point of discharge, all the channels created by him in a split second sweeps the main charge, who had been waiting in Tuchke, the current strength of several hundred thousand amperes while created "BABAAAAH» Plus, the leader often forked or rastraivaytes (do not be sad, the leader, do not worry), creating new and new branches.

The most important of the above for further description: zipper makes the sound "hryas-hryas- ... -hryas-hryas-broads", and the same happens with the light from the lightning.

So let's catch it! H4> «In terms of catch !?" you ask. Well, just a beautiful expression. Actually we wanted to digitize the zipper. We can see it and hear from three different places and by triangulation to reconstruct the whole picture of lightning, the absolute location of the leader at every moment of lightning on a map of the city, as well as its duration being there.



To do this, first you need to take a map of Moscow, and mark on it the point where our bases will be located sensors transmitters. Areas were selected Mitino , Victory Park and Marina Grove

Databases sensors transmitters h4> To see and hear the lightning we bought photodiodes microphones. But it is not simple. Zips in Moscow - it is always rain. Rain for electronics - always death. We therefore greatly spend and bought everything watertight.






For signal processing were purchased three boards Raspberry PI. To transmit the signal from each base station to the host computer used with the USB-modem mobile Internet will not tell what company. Feeding each database was derived from three car batteries.

At each base were used 8 photodiodes arranged in a circle, directed in different directions. The microphone was placed in the center of the circle pointing upwards. Software was programmed so that when the flash appears (assuming flash zadetektiruetsya all base stations simultaneously, which is the beginning of reference), high-frequency starts recording from the microphone.

Installing database h4> We never thought that this would be the most difficult part of the project. To place on the roof of a house though Koszul nose, requires just incredible pile of documents! Resolution expertise permission of the management company, the contract terms, up to minutes of the meeting of inhabitants of the house. Faced with all this, we decided to go another way, the wrong way. Sounding Pizza Man, we went from house to house in the neighborhood of the selected points of the dislocation, looking where to enter illegally the roof. And lo! In the district 500 meters at each point found one such entrance. Lures concierges, we dragged the equipment on the roof, set up and ran home happy ...






We can only wait ...

The first storm h4> Never in my life have I been waiting for a thunderstorm as then. We waited for about a month. And then she went. It happened so suddenly and quickly that we did not even have time to dozharit kebabs in the country, 40 km from Moscow. So fast on the sidelines by traffic jams I've never ridden.

The first signals were awful. It is understandable, microphones tuned anyhow, board programmed too anyhow, because there was no opportunity to test the card with the software. But, thank God, the storm was about 5-6 hours, and we had exactly three. Rushed to the points that housed our database, we started looking for a solution as soon as possible. Right in the porch under the roof (only then I realized that it was possible to do everything at home at a comfortable dry seat, through the terminal). Finally, Sergei, one of our own, set up everything as it should be, and threw us on the source. Compile and execute the program in the next moment the lightning, I realized that everything works perfectly! Oscilloscope traces of the recorded sounds were delightful, especially if filter median filter (filter + light hand for beauty pictures):



Here everything is so obvious that not even need to explain where the leader sneaks through the atmosphere, and where is the main discharge. On other boards appeared quite similar signal with a slight shift of the levels and the volume! Plus, we found that the longer the path that skips the leader, the quieter the sound. Apparently, jumping into small distance is substantially larger current and a diameter greater than heated air, which leads to a loud clap. The situation is somewhat reminiscent of the effect of tunneling.

Look here, now pops lightning! H4> process the received waveform in a software created to Unity3d, we got them ! Lightning! Of course, not without problems. Enumerate the list of problems:

Do not smart enough to take over once the center of sound is not the point where rests the leader, and the middle "channel" that it creates. Very prevented the sampling frequency, the sound of rain and signaling machinery in moment of thunder. On one of the three stations, which we placed deep into the quarter, the average height of the house, madly spoils echo coming from the neighboring houses, and from the ground. Had to be transported to another station house. Requires absolutely precise position of the bases for this, we needed more time to go to our database and record their exact GPS + GLONASS coordinates.


Furthermore! The most amazing is that in the next storm, we counted 8 visible lightning. Thus with thunder flashes was 23, ie, 15 lightning inside the cloud was inaccessible to man. But our station even their digitized! We saw the invisible zipper Here's some more pictures of lightning imposed on Moscow, view from above. If you find here your home, do not worry, no lightning in the house was not hit.








And here's my favorite, and it can crash the program. =)

Finally h4> At the moment, we are preparing a site on which will be online broadcast mode all 3d image of lightning. It will be possible to look at the city from the point of location of lightning, as well as to look like a zipper from his window, compared with the real lightning and ensure accuracy. You can view all the lightning, their exact position and exact time , in which they hit, as well as view the previous thunderstorms and download most favorite lightning. Lightning yet to be processed only for Moscow, but would very much like to expand into other, more rainy city.

Yes, I admit, among other things we still very much disturbed wind, temperature and atmospheric pressure differences in the way of lightning to the microphone, so the ideal automatic digitizing failed. We are confident that the treatment program is lying on 50-100 meters at each point. But still, these 50-100 meters invisible against the background of the overall length of 2500 meters in the lightning. It would be desirable to establish a small weather station with a barometer, a thermometer and a weather vane. Plus microphones have been insufficient on sampling, and they give a lot of noise. Produced by the calculations, we found that for locating lightning up to 20 meters is required for at least another 4-5 stations, refine the results. Plus, it is desirable to put on every station on 2 microphones for clarification.

UPD1: Many habrovchane asked to accommodate more detailed information about the technical part of the project. I am pleased to write, you need a little time.

Source: habrahabr.ru/post/211701/