## 1 Introduction  
Marine magnetic surveys, a non-destructive and cost-effective method, play a crucial role in a wide range of geophysical applications [1; 2; 3; 4]. These surveys are conventionally performed using scalar or fluxgate magnetometers installed on research vessels. Scalar magnetometers provide high-precision measurements of the total magnetic field intensity, while fluxgate magnetometers are valued for their ability to acquire vector components of the magnetic field. These vector magnetic anomalies can clarify the various interpretations arising from scalar magnetic anomaly analysis [5; 6]. However, compared to towed scalar magnetometers, fluxgate magnetometers mounted on ships exhibit lower resolution. This is due to electromagnetic interference originating from the ship's ferromagnetic hull materials and onboard electronic systems, which have limited the conventional use of ship-borne fluxgate magnetometers on cruise missions [7; 8; 9]. Despite these limitations, fluxgate magnetometers have been widely applied in various unmanned platforms such as UUVs (Unmanned Underwater Vehicles) and UAVs (Unmanned Aerial Vehicles) [4; 10; 11; 12; 13], due to their significant advantages of requiring small space and enabling continuous, unattended observation when mounted on vessels. In addition to fluxgate magnetometers, various magnetic field sensing technologies exist, such as Hall-effect, Giant Magneto-Resistance, and Giant Magneto-Impedance sensors [14; 15; 16]. The magnetic sensors for marine magnetic survey require to measure high-resolution magnetic fields due to the ship's dynamic motion changes and also require long-term stability and sensing of low-frequency magnetic fields below 0.01 Hz with a sensitivity of 1 nT or higher. Therefore, fluxgate sensors satisfy all these conditions are preferred [17; 18; 19]. USVs (Unmanned Surface Vehicles) offer advantages over UAVs by enabling longer-duration marine surveys and acquiring higher-resolution data due to their ability to operate on the surface of the sea. Furthermore, they mitigate the risk of losing expensive equipment like UUVs, can effectively explore shallow water areas, significantly reduce operating costs compared to existing manned research vessels, and can autonomously collect data for extended periods even in harsh marine environments, thus being regarded as an innovative platform that can greatly enhance the efficiency of marine surveys [20]. Therefore, USVs are increasingly being explored for high-precision marine magnetic surveys. While one common strategy to mitigate the inherent magnetic noise of a platform is to tow the magnetometer behind the USV to physically separate the noise [21], another approach is to mount the sensor on the vessel and to make the platform using paramagnetic materials to mitigate the magnetic interference. Mounting the sensor directly on the USV offers significant operational advantages compared to towed systems. Specifically, it eliminates the risk of the tow cable snagging on fishing boats and gear, aquaculture facilities, or seabed obstacles, thereby enhancing operational safety and reliability. However, the integration of fluxgate sensors on USVs introduces unique technical challenges, particularly from electromagnetic noise generated by the vehicle's electrical systems and navigation equipment. While paramagnetic materials, such as stainless-steel alloys, have been utilized in deep-tow magnetometer systems to mitigate platform-induced interference [22; 23], their application to USVs remains relatively unexplored. Unlike traditional towed systems, USVs face distinct challenges that require innovative solutions for noise reduction. Consequently, even with hulls constructed from paramagnetic materials, the array of electronic devices integrated into USVs, such as propulsion systems (motors, propellers), power systems (batteries), and navigation and communication equipment, can still introduce electromagnetic interference (EMI) that perturbs the surrounding magnetic field.