This paper describes the principle of computing map magneticdeclinations, a new method of computing MMD is presented.
详细论述了磁偏角自动计算的原理，并提出了一种利用地磁图自动计算图幅磁偏角的新方法。
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According to the specified observation data, it found that the magneticdeclinations on airdrome runway varied greatly; therefore, it couldn't reflect the real condition for the airdrome whole area.