UAG-23A: URSI Handbook of Ionogram Interpretation and Reduction
(second edition)

The URSI Handbook for Ionogram Interpretation contains the agreed standard rules for interpreting ionograms. The publication is known to many as UAG-23A - the volume number it had in the WDC-A for STP publication series on the Upper Atmosphere and Geophysics (UAG). All ionogram interpretation and ionospheric characteristics derived from ionograms are referenced to it.

These rules and conventions have been used, with refinements, since the International Geophysical Year (IGY), 1957-58 when they were produced by "The World Wide Soundings Committee". The first "URSI Handbook of Ionogram Interpretation and Reduction" by W. R. Piggott and K. Rawer was published by Elsevier in 1961. In 1972 the second edition was published as UAG-23. In addition to manual scaling rules for vertical incident ionograms, both documents offered a number of useful discussions about handling ionospheric data, with specific reference to ionogram reduction. UAG-23A, a revision of the first four sections of UAG-23, was also published in 1972. The majority of manual ionogram reduction carried out in the world uses the rules suggested in these publications.

UAG-23A is more than a set of rules and to think of it this way is to miss a vital point. It outlines a number of ways in which ionograms can be interpreted, leaving much latitude for station networks to develop their own basis for interpreting their ionograms. A manual scaler, familiar with UAG-23A advice, can take a complex ionogram, recognise and identify unusual features, thereby developing a consistent interpretation of the ionogram. Using this information, the main characteristics of the ionogram are then scaled. Ideally, any other manual scaler confronted with a similar ionogram will come to the same reasonable interpretation and the resultant scaled characteristics will be comparable between ionosonde networks.

Hard copies of UAG-23A are becoming scarce, yet its value remains as great today as it did when it first appeared. To make this important information available as widely as possible, here is a scanned version.

Thanks to Thomas Ulich ( for producing a complete file with internal links


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