Monday, June 11, 2018

TDoA with propagation delays based on IRI2016 electron densities

This is a follow-up of this blog post where the method referred to there is applied to TDoA maps. The first example is a STANAG 4285 signal (FUO Toulon) centered on 8436.4 kHz (USB: 8432.6 kHz)

TDoA maps using ground-wave propagation delays


TDoA using propagation delays based on IRI2016


The maps using propagation delays based on IRI2016 electron densities match better the (assumed) true position of the transmitter. It is a small effect but noticeable, and can be seen better in the side-by-side comparison below:

TDoA comparison



Another example are the TDoA maps from the last blog post where the TDoA maps based on more realistic propagation delays are more consistent between the two measurements; both indicate a position on the South coast of Cornwall:

TDoA comparison


TDoA comparison


4 comments:

  1. Hi Chris,

    This is really interesting. Any chance you can do a tutorial on how you achieve this? I've seen all the different things you need from your first post, most of which I have. I use KiwiSDR's regularly but don't have one of my own (I already have 4 SDR's and an Icom IC-R8500), but do you need a KiwiSDR to help with this for instance?

    Keep up the interesting work

    Cheers

    Tony

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  2. Unfortunately, the tight summer work schedule does not allow me to take the time to master the TDoA method. But, as soon as there is an opportunity - I will try to do it!
     These days, on the site http://www.radioscanner.ru a stormy discussion ensued (topic address: http: //www.radioscanner.ru/forum/topic12415.html), about the location of the transmitter (s) "The Buzzer" operating at a frequency of 4625 kHz USB. Enthusiasts have identified the coordinates of one of the transmitters - Kerro array 60 18 40 N 30 16 40 E.
     But the analysis of recording signals from different geographically located receivers, produced by enthusiasts of this topic, indicates that synchronously, at one frequency 4625 several transmitters work!
     Christophe, in my opinion, is very interesting, to test the capabilities of the TDoA method in determining the location of the transmitters of the sync network. Will it work?
     73!
    Daniel

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    Replies
    1. Hi Daniel,

      I had a look at the signals on 4625 kHz a while ago and found several peaks in the cross-correlations, suggesting that there is/was more than one transmitter active. But disentangling these is very time-consuming...

      73
      Christoph

      Delete
  3. Hi Tony,

    sorry for this late reply - until I managed to find the right browser settings today, there was a problem replying to comments.

    meanwhile there are a few tutorials available, see, e.g., on kiwisdr.com

    It is not needed to have your own KiwiSDR but it would be very welcome if you could set up one and share it publicly.

    Cheers
    Christoph

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