# A Prediction Model of Marine Geomagnetic Diurnal Variation Using Machine Learning
## 6 Discussion  
The traditional calculation method relies on establishing the geomagnetic diurnal variation model based on spatial position relationships, for example, the distance weighting method is based on the mutual distance of geomagnetic heliostat stations for modeling and projection, the latitude difference weighting is to model the latitude difference of different stations, and the dual weighting factor weighting method integrates the latitude difference and distance for modeling. However, after modeling the geomagnetic diurnal variation trend within a day in Europe, it becomes evident that diurnal variation data exhibit diverse rules across different regions and times, characterized by time-varying complexity. Given the global diversity in diurnal variation patterns, this paper advocates for incorporating short-term prior daily variation information specific to the survey area, along with data from distant stations, to conduct in-depth analysis and unveil underlying relationships. By considering the actual circumstances, a calculation model aligned with the regional geomagnetic diurnal variation law is formulated. This approach imposes fewer restrictions on the positional relationships between stations and aims to capture the true diurnal variation patterns of the survey area more accurately. The data of the traditional algorithm are projected from the daily variation data collected from the closer stations, and it is difficult to reflect the geomagnetic daily variation characteristics by only considering the latitude difference, longitude difference, and mutual distance when calculating, and it is more demanding to select the station location relationship.  
Establishing a long-term offshore diurnal variation station in order to correct diurnal variations in offshore magnetic measurements poses challenges, primarily due to maintenance difficulties and the risk of data loss across the entire measurement section, which often leads to unreliable diurnal variation data quality. One approach to address this issue is to utilize high-quality short-term diurnal variation data collected within the survey area as prior information. By setting up a short-term offshore diurnal variation station, it becomes feasible to obtain short-term diurnal variation information for the survey area in conjunction with data from distant shore geomagnetic stations. In this study, a methodology is proposed to develop a geomagnetic diurnal variation calculation model that captures the true characteristics of both the survey area and the shore geomagnetic stations. Experimental simulations of far-sea magnetic measurement scenarios are then conducted based on the distribution of terrestrial geomagnetic stations. These simulations designate one station as the main station, assumed to be located at sea, with the other stations serving as onshore geomagnetic stations for model verification. The results of the experiments indicate that the model can accurately calculate daily variation information for the actual measurement area over an extended period with high precision. This innovative approach demonstrates the efficiency of leveraging short-term data from the survey area and long-distance shore geomagnetic stations to enhance diurnal variation correction in offshore magnetic measurements. Furthermore, this approach presents lower requirements for geomagnetic day-variable station locations, the ability to adapt to different combined station structures, and improved immunity to the extrapolation of geomagnetic perturbation variations.