海图的基准比例尺是图上一个单位长度与其对应的球面上长度的之比，用分数表示。
The natural scale of a chart is the ratio of a length measured on the chart to a corresponding length measured on the surface of the Earth and is expressed as a fraction.
海图的基准比例尺是图上一个单位长度与其对应的球面上长度的之比，用分数表示。
The natural scale of a chart is the ratio of a length measured on the chart to a corresponding length measured on the surface of the Earth and is expressed as a fraction.
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