HF Source Geolocation Using an Operational TDoA Receiver Network: Experimental Results

Abstract

Determining the geographic location of high frequency (HF) transmitters is of prime importance in both defense and civil operations. In this letter, we present experimental results of distant HF transmitter geolocation performed using the time difference of arrival (TDoA) method. The HF signals considered for our study are transmitted from different locations across Europe. Multiple receivers capable of capturing HF radio signals synchronously are built and a nationwide receiver network with centralized control is deployed in France to assess the feasibility of our approach. HF radio signals are captured simultaneously by all receivers in the network from different European HF broadcast transmitters. From the captured data, the propagation duration differences between the signals received by all receivers are obtained using the cross-channel sounding method. Finally, the transmitter location is estimated using the geolocation algorithm based on the TDoA method. Experimental results demonstrate that it is possible to locate the HF transmitters under favorable conditions with a relative geolocation error ranging from about 0.1 to 10% of the actual ground distance, for most of the experimental scenarios.

An Improved TDOA Method for Land-Based Long-Range HF Skywave Source Geolocation and Experimental Results

“…The proposed method is compared with the existing geolocation methods: (1) The method proposed in [ 12 ] which maximizes the crosscorrelation function to estimate TDOAs in the first step and derives the target location based on Kalman particle filtering, denoted by KPF. (2) The method proposed in [ 13 ] is based on TDOA Quasi-Parabolic mode, denoted by TQP.…”

“…Generally, the propagation path of HF signals is unknown due to the irregularity of the ionosphere. Researchers usually approximate it as a one-hop or multi-hop path model [ 13 ]. The monolayer quasi-parabolic (QP) model is a simple and effective model for calculating the radiation parameters considering an ionospheric medium, defined by the parabolic equation of the electron density versus height.…”

“…The monolayer quasi-parabolic (QP) model is a simple and effective model for calculating the radiation parameters considering an ionospheric medium, defined by the parabolic equation of the electron density versus height. The QP model has been a time-tested means of ionospheric radio propagation analysis [ 14 ], and it has been successfully utilized for HF source geolocation based on the sensor-collected TDOA observations for ionosphere-refracted radio rays [ 13 , 15 , 16 ].…”

“…The method in [ 12 ] proposed a nonlinear filtering algorithm for state estimation with symmetric alpha-stable noise presented, and the average geolocation error is less than 75 km. Multiple receivers capable of synchronizing HF radio signals are built in [ 13 ], and the HF source is estimated using the geolocation method based on the TDOA. These methods achieve high geolocation accuracy under favorable conditions in the experiments.…”

“…These methods achieve high geolocation accuracy under favorable conditions in the experiments. However, these methods assume that the lower boundary of the ionosphere is at the same height everywhere [ 13 ], and require priori or estimated information about the ionospheric virtual reflection heights. Nevertheless, in practice, the ionosphere is irregular and varies in height.…”