(Yesterday, 03:03)sophia2005 Wrote: Hello everyone,
I am curious if placing the Blitzortung device in a dense urban area (many tall buildings, dense electrical system, strong interference) has a significant impact on the accuracy or sensitivity of lightning detection. Does the urban environment cause greater errors than placing the device in a rural or suburban area?
Has anyone on the forum tried to compare data between these two environments?
Welcome to the forum. I see you joined today. My guess is that you are asking at least three different things -- RFI (radio frequency interference) and VLF signal propagation and "errors".
First, let us discuss RFI. I imagine one thing you are asking is, is it difficult to set up a Blitzortung station successfully if the location you have selected is in a dense urban area? And to this, the answer is "it depends". A person who does not have a lot of experience with radio frequency engineering could go to almost any location, urban or rural, and find himself or herself unable to get the station to function as desired. There can be rich sources of radio frequency interference almost anywhere that there are humans.
If the proposed location is a rural location, then I would guess that in a very approximate way, on average, a lack of experience with RF engineering would be somewhat less likely to lead to a lack of success. But just to give a first example, I am in a very rural location, and I have a lot of experience with RF engineering, and when I installed my new Blitzortung station recently, it took me almost three weeks of investigation and experimentation to find a good location and antenna orientation and software settings for my new station that work well.
Some Blitzortung stations are in institutional settings such as universities and schools. But I'd guess the vast majority of station locations are in or around personal homes. If a personal home is (for example) an apartment or townhouse in an urban area, it would not be a surprise at all if it were to turn out that no location for the station will work well. It might be impossible to find any location at or near the home that would be sufficiently free from RFI. To give a second example, right now there is a member of the community located in Europe who has moved from one home to another, and despite having a lot of experience with RF engineering, is unable to find any location in the new home that will permit the member's Blitzortung station to work. The member has offered to give away the station to some deserving recipient in the hopes that in a new location, the station may continue to serve its purpose.
If you were to click around on any of the Blitzortung maps (and I encourage you to do so as part of learning about this fascinating volunteer effort), you would find some high-functioning Blitzortung stations in dense urban areas. If you were to talk with the volunteer operator of such a station, you would probably find that there are multiple factors helping to explain the happy results. It probably includes wise and lucky choices about signal type (E-field or H-field), antenna construction, antenna orientation, and style and type of cabling between the antenna and the station controller. It surely also includes wise and lucky choices about software settings including amplifier gains and signal trigger thresholds. And likely as not, the operator of that station drew upon a lot of experience with RF engineering.
But for every single successful setup of a high-functioning Blitzortung station in a dense urban area by a first volunteer operator, I'd guess there has been another attempted setup of a Blitzortung station in a dense urban area by a second would-be volunteer operator that did not work out well. The second would-be volunteer operator might have the bad luck to have a home in an area that is so rich with RFI that it is just impossible to succeed no matter how much or little luck or wisdom is available.
Second, let us discuss VLF signal propagation. Your mention of "many tall buildings" makes me think that you are wondering whether the many tall buildings might block or attenuate the propagation of the VLF signals. And the answer is "no" or "not nearly as much as one might think".
One of the ways to try to detect a lightning strike is by H-field (magnetic field) reception. The signals that we are trying to receive have wavelengths on the order of 100 km to 10 km. The electromagnetic pulses generated by lightning strikes are so astonishingly powerful that they can be successfully sensed by a station located at a distance of over a thousand km from the strike.
The extremely long wavelengths, and astonishing levels of power, lead to a situation where almost nothing that humans can do, including construction of large numbers of tall buildings filled with steel and other metals, is able to block or attenuate the VLF H-field signals from lightning strikes appreciably. This is what helps to explain how it can be that you can click around in the Blitzortung maps and you can indeed find here and there some high-functioning Blitzortung stations in even the most dense urban areas.
Third, you asked about "errors". I guess one thing that you are wondering is, does it happen that the Blitzortung system makes mistakes in working out where a lightning strike happened, with the mistakes due to the presence of tall buildings or other human-caused aspects of dense urban life? And I think you can appreciate, from my comments above about VLF propagation, that the answer is mostly "no". The signal analysis that is carried out to locate a particular lightning strike draws upon time-of-arrival signal reports from dozens of stations, and the analysis then proceeds to select a dozen of those reports to get the answer. The waves, having wavelengths of tens or hundreds of kilometers, can pass through tall buildings with ease. And even if any single tall building or other human-caused activity were to somehow manage to make trouble for any single time-of-arrival signal report from a single Blitzortung station, the system would still have dozens of other signal reports to draw upon to arrive at a high-confidence strike location the accuracy of which would be undiminished.
But you also asked about whether the decision where to place a particular Blitzortung station (rural or urban) would be likely to somehow cause errors in the location of lightning strikes? Again I think you can appreciate, from my comments above about VLF propagation and RFI, that the answer is mostly "no". The signal analysis, drawing upon signal reports from dozens of stations, is very unlikely to get thrown into erroneous answers about strike location due to an unfortunate choice about where to place any single Blitzortung station. If a particular Blitzortung station were to have the bad luck to perform poorly (and this could be urban or rural, and it could be due to RFI or poor quality of antenna construction or any of a range of other causes), it will simply fail to send useful signals to the server but will not be likely to trick the server into getting a wrong answer about the location of a strike. On the other hand, you can place a Blitzortung station in a dense urban area, and if it has good luck about who is operating it and how they have set it up and configured it, that station can very well generate signal reports that contribute to accurate lightning strike location determinations just as much as the contribution of some other station that is in a rural area.
