Bias real-time correction of airborne frequency domain electromagnetic system based on attitude change

There exists bias for airborne frequency domain electromagnetic instruments which are based on magnetic dipole in the course of flight measurement, and the bias will present nonlinear changes with the change of external air pressure, temperature and other environmental factors and the sway of the transmitter and receiver coils, leading to errors in observation data, so it is necessary to calibrate the bias. The traditional method, “zero field” calibration method, which moves the instrument to a high altitude before and after the flight measurement has a high cost, can be greatly affected by the zone environment, and has low precision by using linear interpolation during the flight. Based on the feature of not varying with the change of attitude angles, the bias of airborne frequency domain electromagnetic instruments can get real-time correction with high-precision during flight measurement by measuring the attitude angles, while meeting the condition of superposed dipole model. The model simulation shows that at the routine flight height of 30m, the precision of bias measured by this method is close to the precision of bias measured at a height of 110 m; the relative error of bias absolute error over the secondary field is less than 5% after correction, meeting the accuracy requirements of ground conductivity inversion. This approach not only reduces the workload and cost of flight, but also can more accurately obtain the nonlinear changes during flight measurement, improving the accuracy of aerial observation data.