 The opposeness of GNSS-based ionospheric tomography affects the stability and accuracy of the inversion results. This issue is addressed by the truncated mapping singular value decomposition, TMSVD, algorithm, which improves both the reconstruction accuracy and computational efficiency. The TMSVD algorithm was tested numerically and compared with the traditional truncated singular value decomposition, TSSD, algorithm. The results show that the TMSVD algorithm is more accurate and efficient than the TSSD algorithm. Furthermore, the TMSVD algorithm is used to reconstruct the ionosphere's temporal spatial variations from GNSS observations under different geomagnetic conditions. The reconstructed results are more consistent with the ionis on data than those of the IRI-2016 model. Therefore, this study demonstrates that the TMSVD algorithm is an effective tool for the tomographic reconstruction of ionospheric electron density, IED. This article was authored by Debayowin, Kung-Yu-Sia, Ingao-Tang, and others. We are article.tv. Links in the description below.