On the Location of Lightning Discharges Using Time Reversal of Electromagnetic Fields
In this paper, we discuss the use of the electromagnetic time reversal (EMTR) method to locate lightning strikes. After a brief description of the EMTR and its application to lightning location, we mathematically demonstrate that the time-of-arrival method can be seen as a subset of EMTR. We propose three different models of backpropagation to address the issue of EMTR not being invariant for lossy media. Two sets of simulations are carried out to evaluate the accuracy of the proposed methods. The first set of simulations is performed using numerically generated fields and the proposed algorithm is shown to give very good results even if the soil is not perfectly conducting. In particular, we show that considering a model in which losses are inverted in the back propagation yields theoretically exact results for the source location. We show also that a lack of access to the complete recorded waveforms may lead to higher location errors, even though the computed errors are found to be within the range of performance of current lightning location systems (LLS). A second set of simulations is performed using the sensor data reported by the Austrian LLS. The locations obtained by way of the proposed EMTR method using only the available sensor data (amplitude, arrival time, and time-to-peak), are observed to be within a few kilometers of the locations supplied by the LLS.