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DIGISONDE-4D
SYSTEM MANUAL
VERSION 1.2.11
SECTION 5 - SYSTEM SOFTWARE 5-21
ARTIST
5:35. The Automatic Real-Time Ionogram Scaler with True height (ARTIST) is an intelligent system devel-
oped for the extraction of ionospheric specification data from ionograms. The automatic ionogram interpreta-
tion (“scaling”) is a computer-hard problem that requires a model of human visual perception to extract useful
ionogram image signatures and a syntactic analyzer to identify and characterize them. Introduction of the
ARTIST in the early 1980s was the single most influential advance in the ionospheric sounding technology that
had brought the Digisonde
®
data outside of a narrow circle of experts into realm of the operational 24/7 space
weather systems.
5:36. INPUT FILES: RSF, SBF. OUTPUT FILES: SAO, SAOXML, MUF.
5:37. A common approach to the ionogram autoscaling in all ARTIST versions is to (1) adaptively threshold
the ionogram image to remove background noise, (2) reduce echoes to edgels (edge elements) corresponding to
the leading edge of the echo, (3) string echoes into traces, and (4) identify traces and determine their character-
istics.
5:38. Digisonde-4D are supplied with the version 5 of ARTIST software. Further details on ARTIST-5 algo-
rithms can be found in [Galkin et al., 2007].
Autoscaling Confidence Level (ACL) of ARTIST-5
5:39. The Autoscaling Confidence Level (ACL) is determined indirectly and automatically by examining the
ionogram features and the autoscaling outcome for various anomalies. Such examination of the ARTIST results
resembles other software solutions that use multiple criteria to spot commonly observed autoscaling problems,
including
• high mismatch of the extracted trace with the trace restored from the calculated electron
density profile,
• unreasonable separation of O- and X-cusps in the F2 echo traces,
• excessive frequency gap between E and F layer traces,
• unreasonably high variability of the scaled values from ionogram to ionogram.
5:40. Since the mid-1990s, a two-digit ARTIST “confidence level” value is routinely provided with each au-
toscaled ARTIST record to help end user applications with automatic accept/reject decisions. Still, independent-
ly of the ARTIST development, other post-evaluation algorithms have been developed to characterize and miti-
gate autoscaling errors. In particular, the USAF QUALSCAN system is used at the Mirrion server in Boulder,
CO to tag out those autoscaled records that did not pass QUALSCAN quality criteria.
5:41. ARTIST-5 software is not only able to check its result using common “sanity checks”, but also to detect
anomalies in the ionogram interpretation process itself. For example, if the F2 trace cusp extraction algorithm
detects the presence of multiple trace segments that are representing the assumed foF2 cusp, confidence in the
correctness of such ionogram evaluation is decreased. Post-evaluation algorithms like QUALSCAN are not
able to sense such complications of the interpretation process.
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