In South Korea, there are about 80 Global Positioning System (GPS) monitoring
stations providing total electron content (TEC) every 10 min, which can be accessed
through Korea Astronomy and Space Science Institute (KASI) for scientific use. We
applied the computerized ionospheric tomography (CIT) algorithm to the TEC dataset from
this GPS network for monitoring the regional ionosphere over South Korea. The algorithm
utilizes multiplicative algebraic reconstruction technique (MART) with an initial
condition of the latest International Reference Ionosphere-2016 model (IRI-2016). In
order to reduce the number of unknown variables, the vertical profiles of electron
density are expressed with a linear combination of empirical orthonormal functions
(EOFs) that were derived from the IRI empirical profiles. Although the number of
receiver sites is much smaller than that of Japan, the CIT algorithm yielded reasonable
structure of the ionosphere over South Korea. We verified the CIT results with NmF2 from
ionosondes in Icheon and Jeju and also with GPS TEC at the center of South Korea. In
addition, the total time required for CIT calculation was only about 5 min, enabling the
exploration of the vertical ionospheric structure in near real time.