HF geolocation and mode estimation with a ULA

The article proposes a method for HF emitter geolocation and mode group range estimation when the signal of interest is received via sky-wave propagation by a uniform linear array (ULA) of antennas. Ionospheric multipath and the geometrical relationships that constrain such propagation are exploited to derive a new estimator for a problem that inherently produces an ambiguous solution when the modes are considered individually. This opens up the possibility to perform meaningful HF single site location (SSL) with a ULA. The method is also applicable to reduce estimation errors in traditional HF-SSL systems based on two-dimensional apertures. Field data gathered in a controlled experiment with known truth is used to validate the method.