Evaluation of 3-D ionospheric tomography from denser GNSS observations in Japan

摘要

3-D ionospheric distributions can be obtained using computerized ionospheric tomography (CIT) from ground-based GNSS observations, but subject to large uncertainties due to limited observations and unknown prior information. IRI-2012 is an ionospheric model, which gives global empirical electron density distribution. In this paper, a two-step CIT algorithm is developed to reconstruct the ionospheric electron density (IED) distribution up to 2000km over Japan using GNSS Earth Observation Network (GEONET) observations operated by the Geospatial Information Authority (GSI) of Japan. Firstly, we update the IRI-2012 ionospheric profiles in Japan using the dense ground-based GNSS observations and ionosonde data. The two parameters are improved through this procedure and the IED is closer to the real value. Then, the updated regional IRI-2012 model is input as a priori value, and the ground-based GNSS CIT is implemented with the multiplicative algebraic reconstruction technique (MART). The CIT results are evaluated by comparing with the independent ionosonde measurements, which shows good reliability and high accuracy.