全球磁场球谐模型NGDC720在局部海域的精度分析

Accuracy analysis of global magnetic field spherical harmonic model NGDC720 in local sea area

全球磁场模型NGDC720是当前分辨率最高的地磁球谐模型之一,对该模型在海域进行精度评估是拓展地磁导航应用的必要前提。本文在顾及NGDC720球谐模型频谱特性的基础上,基于区域船载磁力测量信息对该模型进行精度评估,结果表明:船载磁异常与全球磁场球谐模型NGDC720计算的模型磁异常在整体趋势上是一致的,在该海域的评估精度约为100nT;二者直接比较的标准差为71nT,平滑后二者比较的标准差为42nT,全球磁场球谐模型NGDC720仅能表达中长波磁力信息,该模型不足以表达海域磁力高频信息,但在海洋磁异常应用中可将其作为模型参考场。

The global magnetic field model NGDC720 is one of the highest resolution geomagnetic spherical harmonic models.It is necessary to evaluate the accuracy of the model in the sea area for expanding geomagnetic navigation and other applications.Based on the spectral characteristics of the NGDC720 spherical harmonic model,the accuracy of the model is evaluated based on the information of regional ship bome magnetic measurement.The results show that the global magnetic field spherical harmonic model NGDC720 is consistent with the shipbome magnetic in the overall trend,and the evaluation accuracy in this sea area is about lOOnt.The standard deviation of direct comparision is 71nt,and the standard deviation compared with the smoothed shipbome magnetic is 42nt.The global magnetic field spherical harmonic model NGDC720 can only express medium and long wave magnetic information,which is not enough to express the high frequency magnetic information of the sea area,but it can be used as the model reference field in the application of marine magnetic anomalies.