## 5 Result
### Result Analysis  
The magnetic interference waveforms before and after compensation of calibration data are shown in Figures 20-22. According to the general compensation evaluation standard of airborne magnetic surveys, the quantitative compensation results are shown in Table 5. The standard deviation of interference before compensation is 15.5613 nT and the standard deviation of interference after compensation using the current interference source model is 1.5225 nT. IR is greater than 10. It shows that the current interference source model can compensate most of the magnetic interference generated by UAV electronic equipment, but there is still a certain amount of residual magnetic interference that may be caused by model errors or coupling interference between the power supply current and the aircraft's maneuverability. From the time-domain situation of interference, as shown in Table 6, the peak-to-peak value of magnetic interference before compensation is greater than 180 nT and the peak-to-peak value of magnetic interference after compensation using the current interference source model is reduced to 12.5225 nT. This proves that the current interference source model has an obvious compensation effect on the sudden interference that UAV electronic equipment causes. The magnetic interference waveforms before and after compensation of the actual flight data are shown in Figures 24-26. The coefficients of Table 4 were used for the compensation of the flight data, and the quantitative compensation results are shown in Table 7. In the climbing data, the standard deviation of the magnetic interference before compensation is 64.2361 nT, and the standard deviation of the residual magnetic interference after compensation is 26.9110 nT. In the cruising data, the standard deviation of the magnetic interference before compensation is 53.3411 nT, and the standard deviation of the residual magnetic interference after compensation is 20.6491 nT. In the landing data, the standard deviation of the magnetic interference before compensation is 12.1922 nT, and the standard deviation of the residual magnetic interference after compensation is 6.0670 nT. The compensation improvement ratio is greater than two for all three sets of data. Because the small UAV is limited by endurance and control mode, it was not used to carry out a maneuvering magnetic interference calibration flight. So, the magnetic interference caused by aircraft maneuvers was not eliminated and was reflected in the residual noise. \begin{table}
\begin{tabular}{c c} \hline \hline  & **Current Model Compensated** \\ \hline P–p before compensation (nT) & 185.4457 \\ P–p after compensation (nT) & 12.5225 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: The peak-to-peak value of magnetic interference before and after compensation. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Flight Experiment** & **Std before Compensation (nT)** & **Std after Compensation (nT)** & **IR** \\ \hline Climb & 64.2361 & 26.9110 & 2.3870 \\ Cruise & 53.3411 & 20.6491 & 2.5832 \\ Landing & 12.1922 & 6.0670 & 2.0096 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: The standard deviation and improvement ratio of magnetic interference before and after compensation in flight experiment. \begin{table}
\begin{tabular}{c c} \hline \hline  & **Current Model Compensated** \\ \hline Std before compensation (nT) & 15.5613 \\ Std after compensation (nT) & 1.5225 \\ IR & 10.2210 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: The magnetic interference standard deviation and improvement ratio before and after compensation. As shown in Figures 24 and 26, the magnetic interference of airborne electronic equipment persisted throughout the entire flight process. It can be seen that the magnetic interference waveform is similar to magnetic anomalies signal. After compensation, the magnetic interference caused by most airborne equipment can be significantly eliminated. To sum up, the compensation method proposed in this paper is feasible and effective.