The ionosphere is one of the important error sources that affect the communication of radio signals. The international reference ionosphere (IRI) model is a commonly used model to describe ionospheric parameters. The driving parameter IG12 of the IRI-2016 model was optimally updated based on GNSS-TEC data from 2015 and 2019. The electron density profiles and NmF2 calculated by the IRI-2016 model (upda-IRI-2016) driven by the updated IG12 value (IG-up) were evaluated for their accuracy using ionosonde observations and COSMIC inversion data. The experiments show that both the electron density profiles and NmF2 calculated by upda-IRI-2016 driven by IG-up show significant optimization effects, compared to the IRI-2016 model driven by IG12. For electron density, the precision improvement (PI) for both MAE and RMSE at the Beijing station exceed 31.2% in January 2015 and 16.0% in January 2019. While the PI of MAE and RMSE at the Wuhan station, which is located at a lower latitude, both exceed 32.5% in January 2015, both exceed 42.1% in January 2019, which is significantly higher than that of the Beijing station. In 2015, the PI of MAE and RMSE compared with COSMIC are both higher than 20%. For NmF2, the PI is greater for low solar activity years and low latitude stations, with the Wuhan station showing a PI of more than 11.7% in January 2019 compared to January 2015. The PI compared to COSMIC was higher than 17.2% in 2015.

The development of low earth orbit (LEO) satellites has provided the possibility to improve the accuracy of wide-area global navigation satellite system (GNSS) tomography; however, the existing LEO constellations were not designed to consider the effect on the improvement of the accuracy of GNSS computerized ionospheric tomography (CIT). In this paper, we use simulated observations to reconstruct a global higher-resolution three-dimensional (3D) ionospheric electron density (IED) model with a voxel-based model to explore the combined effects of heterogeneous LEO constellations on CIT. The results are as follows: (1) The number of grids crossed by rays increases after adding LEO satellites at different altitudes, while in the altitude interval of 100–300 km, the gain percentage increases with the number of LEO satellites at all four altitudes (300 km, 500 km, 800 km, and 1000 km). (2) The root mean square (RMS) gain percentages are positive after adding LEO satellite observations at 300 km and 500 km altitudes. Whereas, after adding LEO satellite observations at 800 km and 1000 km altitude, the RMS gain percentages from 100–300 km are negative. (3) From the overall percentage gain, the percentage RMS gain of all six plans exceeds 25%, with planB (96/96/60/30 LEO satellites at 300/500/800/1000 km, respectively) having the smallest percentage RMS gain of 27.31% and planA (192/96/60/30 LEO satellites at 300/500/800/1000 km, respectively) having the largest percentage RMS gain of 32.42%. Considering the LEO satellite launch maintenance cost for the enhancement effect of heterogeneous LEO constellations on CIT, this paper demonstrates that planA can effectively improve the accuracy of the 3D IED model.