HF TDoA multilateration (2)

This is an update to the last blog post where propagation delays from VOACAP are used in addition to great-circle-derived propagation delays.

As VOACAP provides a number of propagation modes (MODE=25) the mode which is most close to the measured time difference is used.

Note that the findings in the plots below might accidentally: when there are enough closely-spaced delays available it is quite likely to match the data.

Nevertheless it can be seen that large deviation from the hypothesis of ground-wave propagation along great-circle paths are due to different reflection heights, i.e.,  1E-1F2, 2F1-1F2, etc: at a given time, a number of different propagation paths are available, and for different combinations of receivers, different propagation modes are in fact observed.

Comparison of measured time delay differences with differences based on ground-wave propagation along great-circle paths and differences based on VOACAP predictions.

Comparison of measured time delay differences with differences based on ground-wave propagation along great-circle paths and differences based on VOACAP predictions.