A procedure for the reliability improvement of the oblique ionograms automatic scaling algorithm

Abstract

A procedure made by the combined use of the Oblique Ionogram Automatic Scaling Algorithm(OIASA) and Autoscala program is presented. Using Martyn’s equivalent path theorem, 384 oblique soundingsfrom a high-quality data set have been converted into vertical ionograms and analyzed by Autoscala program.The ionograms pertain to the radio link between Curtin W.A. (CUR) and Alice Springs N.T. (MTE), Australia,geographical coordinates (17.60°S; 123.82°E) and (23.52°S; 133.68°E), respectively. The critical frequency foF2values extracted from the converted vertical ionograms by Autoscala were then compared with the foF2valuesderived from the maximum usable frequencies (MUFs) provided by OIASA. A quality factor Q for the MUF valuesautoscaled by OIASA has been identified. Q represents the difference between the foF2value scaled byAutoscala from the converted vertical ionogram and the foF2value obtained applying the secant law to theMUF provided by OIASA. Using the receiver operating characteristic curve, an appropriate threshold level Qtwas chosen for Q to improve the performance of OIASA.