蒙城地磁台相对观测磁偏角自2003年8月起,变化较大。运用上海佘山地磁台的资料作对比分析,发现相对观测磁偏角除地磁场的长期变化外,还存在仪器机械性漂移。研究结果认为,这种变化可能是受仪器室的物理因素影响的缘故。 From August, 2003, the changes in magnetic declination of relative observation are large than that before at Mengcheng magnetic station. The contrast analysis of the data of Mengcheng magnetic station with that of Shanghai Sheshan magnetic station shows that, for relative observation of magnetic declination at Mengcheng station, in addition to the long-term relative change of earth's magnetic field, there also exists mechanical drift of instrument and magnetic declination variation at Mengcheng station may attribute to physical factors of observation house.