Expert System for Ionogram Reduction (ESIR)
What is ESIR?
ESIR is a new approach to automated ionogram scaling. It uses a combination of physics-based modeling and knowledge-based pattern recognition techniques to extract traditional ionospheric parameters such as foF2 and hmF2. It also generates electron density profiles (EDPs.) ESIR provides quality and uncertainty indications for these parameters, which enable the user to decide how much confidence to place in the scaled parameters. ESIR is specifically intended to provide suitable inputs to assimilative ionospheric models such as GAIM, but its products can be used for a variety of applications. ESIR development has focused on mid- and low-latitude ionograms.
Ionograms in various formats are converted to a standard ESIR file for analysis. Once in the common format, various quality checks are used to test for adequate trace data, excessive interference, blanketing sporadic E, spread F, and other factors that would impair or prevent scaling. Scaling extracts the E and F parameters and a provides variety of status and quality flags. If the ionogram has adequate quality, the virtual height trace is inverted to obtain a true height electron density profile.
ESIR is designed to work with any vertical incidence ionosonde that produces a conventional virtual height vs. frequency ionogram in the HF range. Several versions have been developed for particular types of hardware, including Vertical Incidence Pulsed Ionospheric Radars (VIPIRs), DISS Digisondes, the Canadian Advanced Digital Ionosonde (CADI), and for ionograms digitized from film archives or other graphic formats.
The basic version does not require hardware separation of extraordinary (X) and ordinary (O) traces. Without this information, there may be ambiguities in identifying traces in some cases, so confidence is accordingly lower.
An improved version that makes full use of hardware X- and O-traces has been developed that gives more reliable estimates of the desired ionogram parameters.
In either case, the geographical coordinates of the sounder and the time of the sounding are required for modeling purposes. ESIR also uses the coordinates to determine the local ionospheric magnetic field needed for X/O-trace analysis.
Outputs are generally produced in plain text format, though other formats such as annotated plots and SAO 4.3 files may also be generated for user applications.
For more information, contact:
Space Environment Corporation
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Rice, D. D., J. J. Sojka, and D. C. Thompson, An Expert System for Ionogram Reduction (ESIR), 2009 CEDAR Workshop, Abstract DATA-02, Santa Fe, NM, June 28-July 2, 2009.
Sojka, J. J., D. C. Thompson, D. D. Rice, Sounding Transformation and Recognition, US Patent No. 7,541,967, US Patent Office, 2009.
[updated 2014-02-18 18:00 UT]