Automatic scaling of critical frequency fof2 from ionograms based on a pixel-following technique

Abstract

This paper proposes a new technique for automatic scaling of critical frequency foF2 parameter of F2-layer from ionograms. Scaling of ionograms initially had to rely on experienced staff for manual operation. In this paper, we have examined ionograms data collected at Chumphon, Thailand, in March 2015, during the period that the observed F2 layer traces can be identified. Our method extracts foF2 value by finding a pixel on the beginning of the trace line and will use this pixel as the starting point for finding the ends of the traces by scanning either one or two lines. In each step we need to prepare the ionogram image, remove unnecessary part of image then remove noise, and refill the trace line before final scanning process. Based on a pixel-following technique, the method produces high accuracy results because it can scan until the final pixel of the trace line. The proposed method has been successfully tested on various ionograms, the results match with a single-pixel accuracy comparing to manual scaling.