Ionospheric correction and integrity algorithms for single-frequency based Satellite Based Augmentation Systems (SBAS) assume that ionospheric vertical delays around an Ionospheric Grid Point (IGP) can be modeled as a combination of planar trend and correlated ionospheric residual field over the trend. Thus the knowledge of residual correlation structure plays a critical role in the algorithm. In addition, ionospheric behaviors vary in each region, and thus it is essential to understand the location specific ionospheric behaviors of regions of interest. This paper analyzes ionospheric residual correlation structure based on additive correlation concept to characterize the correlation structure of the ionosphere over the Korean region. We provide examples of constructing the zeroth-order and first-order models of ionospheric correlations on a typical quiet day (April 18, 2013). This paper also examines the performance achieved by the planar fit algorithm on the quiet day. Based on our preliminary analysis, it is shown that unlike the correlation model for the Conterminous United States (CONUS), the ionospheric residuals after planar fit removal have clear correlation in the Korean region. Thus this paper suggests that correlation structure should be taken into consideration in the development of the ionospheric delay correction and integrity bound algorithm for SBAS in the Korean region.

Keywords: satellite based augmentation system (SBAS), ionospheric correlation model, planar fit algorithm