Comparison of interferometer calibration techniques for improved SuperDARN elevation angles

The high frequency radars in the Super Dual Auroral Radar Network (SuperDARN) estimate elevation angles of returned backscatter using interferometric techniques. These allow ground range to scattering point be estimated, which is crucial for accurate geolocation ionospheric measurements. For accurately it important calibrate interferometer measurements by determining difference signal time delays caused electrical path lengths from main array and at signals are correlated. This delay known as tdiff. Several methods have been proposed tdiff historical observations; these summarised this paper. Comparisons estimates different calibration presented sources uncertainty discussed. effect errors estimated value on accuracy evaluated paper concludes with a series recommendations both scientific SuperDARN data users radar operators.