Effect of Spherical Wavefronts on Very-High-Frequency (VHF) Lightning Interferometer Observations

Interferometric measurements of VHF radio-frequency signals produced by lightning are one of the most effective techniques for studying lightning breakdown processes, so uncertainty and error analyses of interferometric location results have become important topics. Based on the plane wave approximation of lightning RF signal transmission for interferometric location, a geometric model for the systematic error in the interferometric location due to the wavefront being spherical is developed and evaluated for short baseline interferometers, beginning with orthogonal and equilateral triangle baseline layouts. The symmetry of the baseline layout is shown to be helpful for reducing the systematic error caused by the plane wave approximation in interferometric location using a geometric relationship. Furthermore, a baseline layout scheme with the center of an equilateral triangle as the coordinate origin optimizes the systematic error caused by the plane wave approximation.