A new technique was developed to estimate the ionospheric total electron content (TEC) from Global Navigation Satellite System (GNSS) satellite signals. The vertically distributed electron density was parameterized by two thin-shell layers (double-shell approach). The spatiotemporal variation of TEC (strictly speaking, partial electron content) associated with each shell was approximated by the functional fitting of spherical surface harmonics. The major improvements over the conventional single-shell approach were as follows: (1) the precise estimation of TEC was achieved; (2) the estimated TEC was less dependent on the choice of shell heights; and (3) the equatorial anomaly was captured more correctly. Furthermore, higher and lower shells exhibited a different pattern of local time vs latitude variation, providing information on the ionosphere–thermosphere dynamics.

开发了一种新技术，可从全球导航卫星系统（GNSS）卫星信号估算电离层总电子含量（TEC）。垂直分布的电子密度通过两个薄壳层（双壳方法）进行参数化。与每个壳相关的TEC的时空变化（严格地说，是部分电子含量）是通过球面谐波的函数拟合近似得出的。与传统的单壳方法相比，主要的改进如下：（1）实现了TEC的精确估计；（2）估计的TEC较少依赖于壳体高度的选择；（3）更正确地捕获了赤道异常。此外，较高和较低的炮弹表现出不同的当地时间与纬度变化的关系，