Abstract:

In order to increase the accuracy of gradient correction of magnetic measurement and to improve the magnetometer's function, the mathematical feature for the IGRF（International Geomagnetic Reference Field） is described, the complete formula suitable for programming and a program based on Visual C++
is also given. The program can calculate the geomagnetic elements of any position in the world based on the IGRF11 model. Compared with the standard results, the total intensitys mean error of the program is 1.2 nT, which can meet the requirements of the gradient correction. The study also provides a theoretical basis for the development of automatic resonance and PC software.

Key words: international geomagnetic reference field（IGRF）, gradient correction, geomagnetic elements, Schmidt semi-normalized associated Legendre functions