Ionospheric F-layer critical frequency estimation from digital ionogram analysis

Abstract

The ionosphere plays an important role in radio applications, e.g., satellite, cellular phone, global positioning system (GPS), etc. An ionogram is one of the information sources of the ionosphere. Unfortunately, ionograms are generally corrupted by noise and artifacts. These imperfections cause difficulties in the efforts to create automatic systems. In this paper, we propose a size-contrast filtering-based ionogram enhancement. The size-contrast filter can suppress the objects that are too small or too large. The good enhancement performance is achieved by applying the proposed algorithm to the ionograms collected by the ionosonde at Chiang Mai University, Thailand. We also propose a critical frequency estimation algorithm for the ordinary-mode and extraordinary-mode wave components. The proposed estimation algorithm is based on the region of interest selection, and weak segment elimination and trace determination. We achieve very good estimation performance by evaluating our proposed algorithms on ionograms from 2 sets of 12 consecutive sweeps from the nighttime and daytime. © Springer-Verlag Berlin Heidelberg 2007.