The ionospheric mapping function (MF) converts the line-of-sight slant total electron content (STEC) into the vertical total electron content (VTEC) and vice versa, and it is an important function in the creation and use of ionospheric models. Most of the existing MFs are only related to satellite elevation angle, the accuracy is low, and it is necessary to establish a MF with higher accuracy. Therefore, this paper considers the differences of MF for different local time (LT) and DOY (day of year), and uses the Global Navigation Satellite Systems (GNSS) STEC observation data from International GNSS Service (IGS) tracking stations in the northern hemisphere mid-latitude region in 2016–2020 to establish a novel MF model. First, we retrieve the mapping coefficient \(\alpha_{h}\) for different LT and DOY, where the results show significant correlation with LT and DOY, and other periodic variations. Then, we use the empirical orthogonal functions (EOF) to decompose the time series, and the first four order EOF components can describe 98.31% of the total variability. Finally, the periodic function is used to fit the time series of EOF, and a small number of model coefficients are obtained. This work employs the differential STEC of 28 IGS tracking stations in the mid-latitudes of the northern hemisphere in 2020 to verify the accuracy of the new MF and compare it with the widely used modified single-layer model (MSLM) MF. The results show that the accuracy of the new MF is higher than the existing MSLM MF when using JPLG (Jet Propulsion Laboratory’s final Global Ionospheric Maps) to convert VTEC to STEC. Compared with MSLM MF, the RMS of the new MF is reduced by 0.24 TECU on average, and the maximum reduction is close to 0.4 TECU (~ 25%). Among the 28 tracking stations that participated in the verification, the new MF is better than MSLM MF on most days, with 7 stations reaching 100% and 20 stations exceeding 95%. For nearly 60% of the days in 2020, the accuracy of the new MF for all tracking stations is better than that of MSLM MF.

电离层映射函数 (MF) 将视线倾斜总电子含量 (STEC) 转换为垂直总电子含量 (VTEC)，反之亦然，它是创建和使用电离层模型的重要功能。现有的MF大多只与卫星仰角有关，精度较低，需要建立精度更高的MF。因此，本文考虑了不同当地时间（LT）和 DOY（一年中的某天）的 MF 差异，并使用来自北半球国际 GNSS 服务（IGS）跟踪站的全球导航卫星系统（GNSS）STEC 观测数据2016-2020 年中纬度地区建立新的 MF 模型。首先，我们检索映射系数\(\alpha_{h}\)对于不同的 LT 和 DOY，结果显示与 LT 和 DOY 以及其他周期性变化显着相关。然后，我们使用经验正交函数（EOF）对时间序列进行分解，前四阶 EOF 分量可以描述总变异性的 98.31%。最后用周期函数拟合EOF的时间序列，得到少量模型系数。本工作利用2020年北半球中纬度地区28个IGS跟踪站的差分STEC来验证新MF的准确性，并将其与广泛使用的修正单层模型（MSLM）MF进行比较。结果表明，在使用 JPLG（喷气推进实验室的最终全球电离层地图）将 VTEC 转换为 STEC 时，新 MF 的精度高于现有的 MSLM MF。与 MSLM MF 相比，新 MF 的 RMS 平均降低了 0.24 TECU，最大降低接近 0.4 TECU（~25%）。在参与验证的28个跟踪站中，新MF在大多数日子里优于MSLM MF，7个站达到100%，20个站超过95%。在 2020 年近 60% 的日子里，新 MF 对所有跟踪站的精度都优于 MSLM MF。