一、引言一个地磁台的观测质量,主要取决于磁变仪记录的稳定性和绝对观测的准确性。兰州台在整理出版历史资料时,发现磁偏角观测值有明显变小的趋势。本文通过对兰州台1970年— I. INTRODUCTION The observation quality of a geomagnetic station mainly depends on the stability recorded by the magnetometer and the accuracy of absolute observation. Lanzhou Taiwan in finishing the publication of historical data, we found that magnetic declination observed significantly smaller trend. This article through Lanzhou Taiwan 1970 -