地球椭球体表面是曲面，而地图通常要绘制在平面图纸上，因此制图时首先要把曲面展为平面。

Earth is an ellipsoid and its surface is curved, but the maps are usually drawn to the floor plan on paper. So before drawing you must spread the curved surface surface to the plane first.

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地球是一个椭球而非球体。

The earth is a spheroid and not a sphere.

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在大地测量中，地球的形状被看成一个椭球体，虽然在技术角度来看，它不是真正的椭球。

In Geodetic Surveys, the shape of the earth is thought of as a spheroid, although in a technical sense, it is not really a spheroid.

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在大地测量中，地球的形状被看成一个椭球体，虽然在技术角度来看，它不是真正的椭球。

In Geodetic Surveys, the shape of the earth is thought of as a spheroid, although in a technical sense, it is not really a spheroid.

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