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Ionogram Interpretation as Image Recognition
Bakhitzhqan Dj. Chakenov and Alla P. Chakenova
Alma-Ata, 480068, Kazakhstan
(Phone: (8 3272 65-80-82, Fax: (7 3272) 63-12-07 (or 63-69-73))
Complicated visual image recognition is possible due to isolation contours, ie. the high-frequency components present in the space-frequency spectrum of an image make it possible. Sudden disappearance of the image fragments and a distorted image perception occurs while the sensory signal is extinct. An image then becomes fixed relative to the retina. In this case, the eye movements not only refresh the perception, and help to see the more fine details due to arrival of information about high spatial image frequencies, but also suppress the previous stimulus signal. The highest keenness of sight then takes place, presenting the images for 400-600 ms. Perceptional organisation occurs in distinguishing between figure and background. Any groupings possessing special features can serve as "units". Similar element clots, or periodical pattern gaps, can be taken as "figures". The regions with homogeneous distribution of illumination intensity and different textures are singled out. A coherent picture comes out after sensory information integration. Contextual information using ionogram redundancy (particularly their availability for the subsequent time intervals) makes it possible to draw attention selectively to separate fragments of the height-frequency time-changed profile and to concentrate on key elements. If in an ionogram some details are absent, then conventional elements can be substituted, e.g. line segments of a suitable length. The shape, dimensions and orientation of these elements can be chosen from a typical ionogram image, which would relate to a given time, season, and solar activity level. More intensive usage of a short-term image memory (duration of an exact and full ionogram image lasts about 1s) gives an operator an additional advantage, while matching the two fast changing ionograms. Line orientation information retains fuller volume than the complicated figure shape and the complicated signs do not stay in short-term image memory. The inner observer's models formed according to logical criteria  are compared with visual information.
An operator's work quality depends much on images presenting parameters (sharpness, contrast range, brightness, exposure, colour, signal/noise relation, size, orientation). The operator has a section reference book at his disposal (E, Es,...F1, F2). A sign reference book includes a slope of ionogram trace, an interval between 0- and X-mode critical frequencies. Data on trace dimensions, its general shape and context information can be combined. In addition, small parts of an ionogram should be analysed simultaneously and in detail .
1. URSI Handbook of Ionogram Interpretation and Reduction, 1961.
2. B. Dj. Chakenov, Wave Processes in the Ionosphere, A.-A., 1987.