## 1 Introduction  
The UAV aerial magnetic survey is a method of detecting weak magnetic anomaly signals of underground or underwater targets by using a UAV equipped with a high-precision magnetometer to scan doubtful areas [1]. Compared with a manned vehicle, a UAV has the advantages of convenient takeoff and landing, small size, low flight cost and high safety, so it will become the main development trend in the future for UAVs to replace traditional manned vehicles for underwater antisubmarine detection and unexploded ordance detection [2, 3, 4, 5]. However, the electronic equipment in UAVs is highly integrated as the space limited and most of them are driven by electricity, so the electromagnetic environment of the UAV platform is complex [6, 7]. Research shows the strong magnetic interference of about 100 nT that small UAVs produce near the magnetometer during operation [8]. This seriously affects the quality of aeromagnetic observation data. The traditional aeromagnetic compensation algorithm based on the T-L model can only compensate the magnetic interference generated by the ferromagnetic materials and conductive materials of the aircraft platform under the maneuvering action of the platform [9]. This does not effectively describe the magnetic interference generated by airborne electronic equipment, so it is difficult to achieve good results using the small UAV platform. For the magnetic interference caused by airborne electronic equipment, [PERSON] optimizedthe switching power supply circuit of the aeromagnetic system of a UAV and reduced the electromagnetic interference of the body power supply in [10]. In [11], [PERSON] proposed a technology to optimize the arrangement of each motor on the body. He did this by modeling the magnetic field of a single servo motor as a single permanent magnet dipole and then using genetic algorithms to find a combinatorial optimal configuration for the servo motor. [PERSON] proposed a real-time dynamic compensation method in [12] to eliminate the weak magnetic interference caused by onboard electronic (OBE) equipment and verified the effectiveness of this method in the laboratory. In [13], a cancellation algorithm was proposed to remove any ON/OFF effects in the magnetic data while recovering the original data to its normal trend. It is a postprocessing method and is not suitable for real-time compensation. In [14], the author proposed to use OBE sensors to measure the equipment current and compensate the weak magnetic interference of about 0.2-1 Hz caused by beacon lights on a manned vehicle. [PERSON] used the aeromagnetic system of the four-rotor UAV to design static and dynamic tests and found the correlation between the frequency of electromagnetic interference signals and the rotation frequency of the UAV motor [15]. This research has certain significance for weakening the electromagnetic interference of the aeromagnetic system of a UAV. In [16], [PERSON] built a simple magnetic field scanning device to draw a magnetic field distribution map of the body. Using this scanning device, the authors carried out magnetic interference tests on UAVs. The test results showed that the magnetic interference fields of fixed airfoil UAVs were mainly concentrated in the nose and tail of the engine, battery and servo motor. [PERSON] proposed a novel noise reduction method of UAV magnetic data based on complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN). However, several intrinsic mode functions (IMFs) of CEEMDAN do not have clear physical meanings [17]. In order to eliminate the magnetic interference of UAVs and improve the aeromagnetic data quality of UAVs, this paper analyzes the causes of magnetic interference generated by airborne electronic equipment and studies the characteristics of magnetic interference under different operating conditions using ground experiments. It was found that the magnetic interference of airborne electronic equipment is similar to that of permanent magnet materials and its amplitude is related to the supply current.