The International Geomagnetic Reference Field (IGRF) model is a combination of the several models developed by independent groups of scientists using different approaches for the selection of input data and methods for calculating harmonic coefficients. This approach allows for mutual comparison of individual models and for their combination to obtain the most reliable values of the harmonic coefficients. This letter provides a brief description of methods for building the IZMIRAN Earth’s main magnetic field model, submitted to the IAGA Working Group V-MOD for creating IGRF-13. Special efforts were made to obtain as uniform coverage of the entire Earth’s surface as possible with observations. The surface was divided into a grid of approximately equal cells. Then the data for geomagnetically quiet intervals were placed in the corresponding cells and a median filter was applied to select the data in each cell. Spherical harmonic coefficients up to degree 13 were calculated for the interval 2014-Jan to 2019-Aug with a time step of 10 days and extrapolated to 01.01.2010.

国际地磁参考场（IGRF）模型是由独立的科学家小组使用不同的方法选择输入数据和计算谐波系数的方法开发的几种模型的组合。这种方法可以对各个模型进行相互比较，并可以进行组合以获得最可靠的谐波系数值。这封信简要介绍了IZMIRAN地球主磁场模型的构建方法，该方法已提交给IAGA V-MOD工作组以创建IGRF-13。为了通过观察获得尽可能均匀的整个地球表面覆盖率，我们做出了特别的努力。将表面分成近似相等的单元格的网格。然后将地磁静默间隔的数据放置在相应的单元格中，并应用中值滤波器选择每个单元格中的数据。计算了2014年1月至2019年8月之间的时间间隔为10天的最高为13度的球谐系数，并推断到2010年1月1日。